External moisture A guide to weathertightness remediation

Transcription

1 External moisture A guide to weathertightness remediation To be read in conjunction with Acceptable Solution E2/AS1

2 This document is intended as guidance only and is issued under section 175 of the Building Act While the Department has taken care in preparing the document, it should not be relied upon as establishing compliance with all the relevant clauses of the Building Act or Building Code in all cases that may arise. This document is not a Compliance Document and may be updated from time to time. The latest version is available from the Department s website at

3 Foreword In recent years, some New Zealand timber-framed buildings have been designed and built in ways that have caused weathertightness problems. The Department of Building and Housing is working to ensure better standards of construction, and to make consumers more aware of housing and construction issues. This involves a variety of measures, such as supporting homeowners under the Weathertight Homes Resolution Services Act 2006, publishing guidance about buying, building and maintaining homes, and improving weathertightness construction practices. This latest publication by the Department is a consultant s guide to weathertightness repair, entitled External moisture A guide to weathertightness remediation. It outlines a process that consultants should follow when advising owners on weathertightness repair of buildings. Specialist areas are also highlighted, where the experienced specialist can assist with critical aspects in the remediation process. These include help with investigating the specific cause and extent of leaks, with deciding repair strategies and with analysing decay. External moisture A guide to weathertightness remediation also tells builders and building officials about the intricacies of weathertightness repair, and informs owners of the procedures and specialist advice needed to repair timber-framed buildings affected by water entry. This is a technical document that has been developed in cooperation with a range of technical experts working in different areas of remediation, including building specialists, designers, remediation contractors, building officials, building scientists and fungal decay experts. It therefore represents a broad industry view that will provide a useful benchmark for remediation work. The Department recommends External moisture A guide to weathertightness remediation to consultants advising owners on weathertightness repair of buildings and to anyone who is interested in weathertightness. WEATHERTIGHTNESS remediation 1

4 INTRoducTIoN 6 Format of the guide 6 Background to the guide 8 Weathertightness and durability in the Building Code 8 Understanding weathertightness and durability 9 1 General information collection stage The property The building The site The current weather Construction history The owner or client Other information Information within the remediation process 15 2 Diagnosis stage The diagnosis process Steps in the diagnosis process Step 1: Visual investigation Step 2: Non-invasive testing Step 3: Invasive testing Step 4: Cut-outs and sampling Step 5: Identify leak sources Diagnosis conclusions Damage assessment Identifying and repairing causes of leaks Costs Reporting 23 3 Design stage Introduction Current state of active defects Nature of active defects Systemic defects Limited defects Isolated defects Potential for future damage Building leaking on some walls Apparently dry building 29

5 3.5 Repair priorities Importance of remediation Repair priority Staging of remediation work Design-related issues Reducing risks Visual effects Town planning considerations Other issues Cost-effectiveness Ongoing maintenance Alternative strategies Sketch options Implications of alternate strategies Choosing a strategy Project programming Estimates and budgets Developing the sketch design Contract documentation Working drawings Technical specifications 41 4 Contracts and construction stage Tender type The tender documents General conditions of contract Specific conditions of contract Important specific conditions Documentation and compliance General roles and responsibilities Occupancy and insurances Contract payments Special protection requirements Construction activity issues During construction Contract administration General review Contract changes and uncertainties Substantial completion 52

6 5 Post- construction stage Contract completion Post-contract matters Project information Maintenance and monitoring Planning for renewal 55 Appendix 1: Areas of risk 56 Appendix 2: Timber rot and moulds 59 A 2.1 Before inspection 59 A 2.2 During inspection 60 A 2.3 Laboratory analysis 62 A 2.4 Using analysis results 63 Appendix 3: Checklist for information collection 64 Appendix 4: Additional resources 66 Glossary 67

7 Figures Figure 1: The format of the guide 7 Figure 2: Weathertightness in the Code 9 Figure 3: Common areas of weathertightness risk 10 Figure 4: The building 11 Figure 5: The site 12 Figure 6: The records 13 Figure 7: The diagnosis stage 17 Figure 8: The diagnosis process 18 Figure 9: Moisture readings 20 Figure 10: Leak sources 21 Figure 11: Likely extent of timber decay and damage 22 Figure 12: The design process 25 Figure 13: The nature of defects 27 Figure 14: Visual effects 34 Figure 15: Town planning issues 34 Figure 16: Contracts, construction and beyond 43 Figure 17: A basic maintenance manual 54 Tables Table 1: Risk of leaks and consequences of failure 30 Table 2: Reducing the risks 33 Table 3: Implications of alternative measures 37 Table 4: Project budgets over time 39 Table 5: Common weathertightness defects 56

8 Introduction External moisture A guide to weathertightness remediation (the guide) provides an explanation of the process, documentation and project management needed to repair weathertightness defects successfully in timber-framed construction in New Zealand (refer to Building types covered ). Purpose The purpose of this guide is to provide assistance to consultants as they embark on weathertightness remediation work. It also aims to promote consistency in the way consultants assess weathertightness problems, make recommendations, detail and specify repairs, and implement remediation projects. Building types covered Although generally oriented towards housing, this guide will also prove useful for other types of timber-framed buildings (or parts of buildings). When the construction is appropriate, the guide should be useful for the following types of buildings. Housing Communal residential buildings (as defined in NZBC clause A1) Communal non-residential Buildings Light commercial buildings Industrial buildings Limitations This guide recommends the use of consultants as the most appropriate way to proceed with planning for and implementing remediation work. Most remediation projects involve complex technical and contractual issues that are beyond the skills and experience of most building owners. If owners are considering undertaking the work, they should expect to have to exercise the functions and judgement of an experienced consultant, and must be aware of the potential risks that the work will not be properly diagnosed or repaired if professional advice is not sought. The information provided in this guide does not replace professional advice. Guidance incorporated into remediation repair work must be reviewed by knowledgeable consultants, to ensure that the unique conditions and design of the particular building are reflected. The use of the guide does not relieve consultants (or building owners) of their responsibility to comply with the Building Act 2004, the New Zealand Building Code, relevant New Zealand building Standards and other Acts, local bylaws and professional obligations. Issues relating to claims, litigation or similar matters that might be involved in some remediation projects are not addressed in this guide. Other New Zealand Building Code issues This guide focuses on moisture and associated durability issues. It must be noted, however, that other Building Code issues (such as fire safety, structure and so on) need to be considered along with the moisture problems. Audience The primary intention of the guide is to provide guidance on the overall remediation process for: architects, engineers and other building professionals weathertightness building consultants. The guide should also provide some useful background information for: building owners or managers builders involved in remediation work building specialists building officials legal advisors insurers and financiers. format of the guide The guide identifies the general stages and the range of activities that must be carried out within a remediation project and decisions that must be explored. The stages are not neatly separated, instead they overlap, and include various feedback loops when more information becomes available as the remediation project progresses. Early in the remediation process it is important that building consultants use their experience to assess the likely extent of the repair work early so that 6 WEATHERTIGHTNESS remediation

9 owners can base their decisions on likely overall costs and repair options. As the project progresses, more information is gained on the underlying construction and condition of the building, which often results in the reassessment of earlier decisions. This iterative (see glossary) process continues into the construction phase, when hidden construction elements are finally revealed. The gradual decrease of uncertainty is particularly important in remediation work, because it can significantly affect budgets, schedules, consents and final construction. The unknowns that apply to various stages of the process must be taken into account during client consultations, budget preparation, when developing contract arrangements, when selecting contractors and when anticipating amendments to the consent documentation. The broad stages of the remediation process are described in sequence within the guide, as shown in Figure 1. Additional detailed explanations, examples and reference information are provided in the appendices. Boxes are used throughout the guide to provide further information, and the yellow boxes provide additional hints and warnings about possible pitfalls in remediation projects. Figure 1: The format of the guide Companion documents External Moisture A guide to using the risk matrix Stage 1 Information collection Gathering relevant data Refer Section 1 (page 11) Diagnosis of Buildings for Weathertightness Stage 2 Diagnosis Inspecting Moisture testing Sampling and analysis Refer Section 2 (page 16) External Moisture An introduction to weathertightness design principles Stage 3 Design Managing risks Developing design solutions Documenting for construction Refer Section 3 (page 24) Stage 4 Contracts and construction Developing suitable contracts Completing the repair work Refer Section 4 (page 42) Stage 5 Post-construction Maintaining weathertightness Refer Section 5 (page 53) WEATHERTIGHTNESS remediation 7

10 Terminology The glossary at the end of this document explains many of the terms used throughout this guide. The following are frequently used abbreviated terms. Department the Department of Building and Housing Building Act (or Act) the Building Act 2004 Building Code (or Code) the New Zealand Building Code (NZBC) Consultant the person advising a building owner on remediation contract work BCA building consent authority (the local council that issues building consents, carries out inspections during construction and issues code compliance certificates, notices to fix and compliance schedules) Companion documents There are several companion documents (as shown in Figure 1) that should be read in conjunction with this guide and that provide useful information for surveyors and consultants on weathertightness remediation. External moisture a guide to using the risk matrix provides additional information on weathertightness risk assessment. Its application to remediation projects is discussed further within this guide. Diagnosis of Buildings for Weathertightness is a more detailed report intended to be used by building experts who are commissioned by the Department of Building and Housing to investigate and diagnose the weathertightness of a building for Determinations and Weathertight Homes Resolution Services. Diagnosis results can be used directly as the first step in remediation design, or indirectly by contributing to dispute resolution activities. External moisture An introduction to weathertightness design principles explains the principles behind the E2/AS1 details in order to provide a basis on which alternative weathertight details may be designed. background to the guide The successful repair of weathertightness defects is developing into a specialist area within the inspection, design and construction sectors of the building industry. Although steps have been taken to improve the weathertightness of new buildings, existing moisture-troubled buildings (or buildings that owners seek assurance about) still require attention. The focus of this guide is on the remediation process, rather than rules to be followed. Successful remediation design and construction is an iterative process that is shaped by the particular circumstances of each situation. Success also relies on the experience of the consultants and specialists who have been contracted to do the work. Weathertightness and durability in the building code Figure 2 shows how weathertightness and durability requirements fit within the Code. The Department issues Compliance Documents that set out prescribed methods of complying with specific clauses of the Building Code. However, following these prescribed methods is optional. Remediation work involves many situations outside of those covered by the E2/AS1 details. Performance-based alternative solutions for sitespecific circumstances will need to be developed. Alternative solutions are subject to acceptance by building consent authorities (BCAs). A remediation consultant must satisfy the BCA that the repair details will meet the requirements of the Building Code. 8 WEATHERTIGHTNESS remediation

11 Figure 2: Weathertightness in the Code Must be followed Building Act Building Regulations Building Code New Zealand Building Code Clauses: E2 External Moisture (current) B2 Durability (ongoing performance) Many details in remediation work Weathertightness risk At all stages of a successful remediation project, consultants must be able to recognise and assess the general and specific weathertightness and durability risks of a building. General risk factors must be understood and specific high-risk areas of the particular building must be identified. Once the risks are identified and understood, the consultant can then pay particular attention to those areas that are known to have an increased likelihood of leaking. Further detail Table 5: Common weathertightness defects Compliance Documents E2/AS1 and E2/VM1 Alternative solutions (performance-based) The management of known weathertightness risks begins at the diagnosis stage (when potential sources of moisture penetration must be identified and investigated), and should extend through the design stage to the construction stage. Pathways for remedial work Common areas of weathertightness risk are shown in Figure 3. understanding weathertightness and durability Consultants involved in remediation work need to understand and use weathertightness and durability principles in all stages of the remediation process. This guide builds upon the background information provided in the companion document External Moisture An introduction to weathertightness design principles, which is recommended for further guidance. WEATHERTIGHTNESS remediation 9

12 figure 3: common areas of weathertightness risk 1 Base clearances 2 Vertical control joints/cracks 3 Horizontal control joints 4 Horizontal joints corners 5 Cladding base 6 Intercladding junctions 7 Sheet joints 8 Material quality 9 Cladding top 10 Decorative bands 11 Corners 12 Window jambs 13 Window sills 14 Window sill/jamb junctions 15 Window head/jamb junctions 16 Window heads 17 Raked/curved window heads 18 Garage door heads 19 Garage door jambs 20 Garage door jamb bottom 21 Parapet/roof junctions 22 Parapet tops 23 Parapet top corners 24 Rainwater outlets 25 Downpipe spreaders 26 Roof edge/gutter 27 Wall/roof junctions 28 Apron flashing bottom 29 Roof to wall clearances 30 Other roof flashings/skylights 31 Inter-roof claddings 32 Inter-roof/wall junctions 33 Deck/wall junctions 34 Deck perimeter/wall junctions 35 Deck perimeter 36 Open balustrade/wall junction 37 Clad balustrade/wall junction 38 Clad balustrade top 39 Handrail fixings 40 Deck drainage/overflows 41 Balustrade/deck junction 42 Timber deck/wall junction 43 Pipe penetrations 44 Pergola fixings 45 Meterboxes/grilles Note: Additional and/or different areas of risk apply to other design forms or materials such as solid masonry or masonry veneers, solid timber walls, timber subfloors etc WEATHERTIGHTNESS REmEdIATIoN

13 1 General information collection stage The collection of general information about the building early in the remediation process will help consultants direct attention to areas that are most at risk of leaking. Figure 4: The building Some information should be available from the BCA records, while further knowledge can be gathered by exploring the neighbourhood. A street-side perusal with photographs taken is useful for assessing general features of the building and site. Information should be sought on the age and history of the building (including the building materials used, timber type and degree of any timber treatment), component installation dates, leak history, details of past maintenance and any previous repairs. 1.1 The property When consultants inspect a property, they should pay attention to those particular characteristics that are likely to influence the building s weathertightness and durability. E2/AS1 Risk Matrix East Elevation Risk factor Wind zone (per NZS 3604) Risk severity Low Score Medium Score High Score Very high Score Subtotals for each risk factor further detail Figure 3, Table 5, Appendix 3: Checklist for information collection The building Type of building detached house, multi-unit complex, other type Foundations concrete, timber, subfloors, retaining walls etc Walls cladding materials, framing type, timber treatment, fire ratings, bracing etc Windows and doors materials, installation, special types (such as box/corner windows, raked /curved tops, fire ratings) Decks numbers, types, floors, balustrades, fixings etc Roof material, slope, levels, design features Other features parapets, clad columns/beams, framed chimneys, decorative bands, cornices, plinths, pergolas etc Number of storeys Roof/wall intersection design Eaves width Envelope complexity Deck design Total risk score: 19 The E2/AS1 risk matrix can be used to assess general risks applying to each elevation and whether a similar design would now require a drained cavity to comply with E2/AS1. Further detail External Moisture A guide to using the risk matrix WEATHERTIGHTNESS remediation 11

14 1.1.2 The site Location Salt-laden air affects the durability and maintenance needs of elements such as metal components. Very cold locations can also present special conditions for a building to cope with (such as movement resulting from extreme temperature changes and the ability to withstand moisture resulting from snow melting). Wind zone The wind zone may be moderated or increased by local factors such as site slope, trees and buildings (refer to NZS 3604 section 5.2 for guidance). Prevailing wind and rain Wind-blown rain will affect parts of buildings differently depending on local shelter, prevailing weather patterns and the terrain (hills create localised wind conditions). Slope The slope of the site affects surface water drainage and exposure, depending on the prevailing wind and rain. Orientation Sunshine and wind can promote the drying of claddings. However, sunshine also contains ultraviolet light, which can prematurely degrade some claddings, components, sealants and paints. Figure 5: The site Sun orientation Rain Wind other buildings The current weather Weather and seasonal effects A prolonged dry spell combined with a type of construction that aids drying can often mean that there is little or no evidence of high moisture levels from the readings taken with a standard resistance type deep- with the probe moisture meter. Moisture levels can also change significantly season, and can often be much lower in areas of advanced decay. The season and weather can affect moisture testing results. These influential factors must be recorded and planned for. The weather patterns over the 3 to 4 weeks before the inspection should be established. Allowance should be made for possible seasonal effects, and the time period for a survey may need to be extended to allow testing during seasonal wet weather or particular wind directions. 1.2 construction history A building s construction history can provide consultants with a basis for considering the results from diagnosis investigations and to then assess repair options during design. Consent documentation Where possible, copies of drawings, specifications and any approved amendments to the building consent should be obtained. Details and specifications relating to cladding and timber framing and any information about designers, engineers and builders may be useful. Resource consent records should be checked for any conditions relevant to the remediation diagnosis and design. height vegetation ground water salt air ground contours 12 WEATHERTIGHTNESS remediation

15 Figure 6: The records Property file Resource Building Consent consent Building specification Consent drawings Inspection records Claddings Producer statements Warranties Technical details Appraisals Other information Certificates Timber invoices Past repair work Letters and statements Code compliance certificate Age of construction Accuracy of records While consent documents show original design intentions, supporting evidence is also needed because the final details and materials may have varied significantly from those shown in the original drawings and specifications. A copy of the building consent and any code compliance certificate should be obtained. Copies of inspection records and reports should be sought (including any indicating the designer s role during construction). An assessment should be made on when the building was occupied (as distinct from completed according to the code compliance certificate), as this indicates the age of components in the building envelope and also the likely construction techniques common at the time. Timber treatment Evidence of the level and type of any timber treatment should be noted, as this is critical for informing later decisions on likely moisture damage and remedial options. As the specification alone is not sufficient, other supporting evidence (such as letters, statements, invoices etc) should be sought. However, it must be remembered that the only reliable evidence comes from removing timber samples and having these laboratory-tested for treatment types and levels. Further detail Refer A 2.3: Laboratory analysis WEATHERTIGHTNESS remediation 13

16 Producer statements and other information The age of the cladding The age of cladding is important for assessing its current condition. The cladding completion date can be significantly earlier than the building s completion. The completion date should also indicate the manufacturer s technical details that should have been used at the date of installation. Copies of any technical information, producer statements and warranties should be sought, particularly the manufacturer s information about the external claddings and coatings used on the building. These records should help to identify the materials that should have been used (which may differ from those specified in the consent documents or from those actually used). They may also show the completion date of those parts of the work and the age of the elements (eg, the wall cladding). Past repair work Evidence of any past repair work should also be sought. If consented work was undertaken, the date, location and details available on the repair work carried out should be noted. 1.3 The owner or client Understanding the owner or client s situation provides the consultant with a context for assessing remedial options during the design stage. Some general information can be collected prior to initial meetings with the client (saving time and informing discussions). Nature of ownership Clarification of the ownership and areas of responsibility for managing maintenance is important. This can affect later decisions and the time needed for client decisions and approvals. If the building is a detached house, is the client the occupier, or is the house tenanted? If the building is a multi-unit complex, is the client a Body Corporate or an individual owner of one of the units? (Refer to Complexities of ownership ). Reason for seeking advice Is the building currently leaking, or is the owner concerned about the possibility of hidden or future leaks? Beware the quick fix Beware pressure for a quick fix from an owner planning to sell. A consultant should not be party to substandard repairs. A sale could later be challenged if these repairs prove ineffective in preventing leaks and damage results. Recommendations must be based on results of the investigation, not just on an owner s short-term wishes. Occupants Gather any available information from occupants about the building and its problems (refer to Gathering further information ). Complexities of ownership In a multi-unit complex, confirming ownership of common property is critical to the owners decision-making processes and to the apportionment of costs to various owners. If the client is one of multiple unit owners, this introduces complications when repairing party walls. Body Corporate rules and restrictions must also be clearly understood. Similarly, cross-leased properties can mean there are restrictions over individual properties (depending on the terms of the leases), which must be investigated and provisioned for. Underlying motivation If an owner intends to sell the property in the shortterm (and wants a code compliance certificate), they may be aiming to spend as little as possible. The consultant must be prepared to explain their obligation to comply with the Building Code. Building Code requirements are a minimum. If intending to keep the property longer term, an owner may want to meet higher standards to reduce future maintenance requirements, to provide future insurance and peace of mind, or to improve the image of the building for future resale value. 14 WEATHERTIGHTNESS remediation

17 1.4 other information Property value A building s value can affect decisions as to the type, extent and even the viability of remediation work. Information on building values may be useful when considering remedial design options. In an extreme situation, the repair of a badly damaged building may prove not to be economically viable if the costs of repair outweigh the replacement cost. Gathering further information Information from occupants Outline some standard questions, such as: Can you show me any indication of water damage and other weathertightness concerns you have about the house? Has any repair work been done? Do you have any builder s, supplier s and/or manufacturer s warranties? (And ask for any further relevant information.) Other associated people Also try to identify people/companies involved with the design, approval and construction and any previous remediation of the building (and seek contact details if available). 1.5 Information within the remediation process While initial information collection is described as a stage in the remediation process, it is not an activity that can be separated from the overall remediation process. As a project progresses through subsequent stages, further detailed information must be collected to confirm, adjust and add to the consultant s knowledge. The initial collection of general information is actually the beginning of the diagnosis stage, which is explored in the following section. Sales history The sales history of the property may also provide information. Sales histories that cover the past decade or more are commonly available for detached houses or units. Frequent sales of the property could indicate ongoing problems that need investigation. Other reports If past sales have occurred, these may have involved pre-purchase inspection reports. Other types of building assessments may also have been carried out (such as for a determination). Copies should be sought, as important information may be revealed that could inform the remediation process. However, historic reports should always be treated with caution and do not eliminate the need for further assessments. WEATHERTIGHTNESS remediation 15

18 2 Diagnosis stage The diagnosis stage is the investigative part of the remediation process, and Figure 7 shows how the early collection of general information contributes towards this stage. Further detail Section 1: General information collection stage This section outlines the diagnosis process for consultants. Remediation experience is essential for this diagnosis stage to ensure the adequacy of testing and assessment of evidence. Consultants may wish to engage the assistance of experienced remediation specialists to assist with this diagnosis. This will help ensure the reliance of conclusions on which subsequent remediation work for the project is based. The following general aspects should be noted. Expertise Remediation specialists should be experienced and show evidence of past involvement in successful remediation projects and possibly in training courses. (The New Zealand Institute of Building Surveyors offers specialist remediation training for members.) Other qualified specialist expertise is needed for timber and mould analysis, corrosion, structural issues, and other associated areas such as acoustics and fire protection. Destructive testing The consultant should clearly establish with the owner the extent of inspection (refer to Types of surveys ), including any destructive testing, cladding removal and sampling required. Inspection equipment Particular equipment is needed for activities such as gaining access to all areas of a building (including subfloor and roof spaces), photographic recording, moisture testing and opening up parts of the cladding. Ongoing testing and observation may also be needed for difficult-to-diagnose moisture problems. Health and safety Building investigations can sometimes reveal decay of a severity that is threatening to the structure of critical building elements. This requires immediate engineering advice and action, such as temporary repairs, structural propping, closing off certain parts of the building and consulting with the BCA. The removal of claddings or linings may reveal moulds that can pose health hazards to the repairers and occupants. Specialist advice is needed on mould identification, likely hazards and treatment. Types of surveys For practical purposes, the guide assumes two levels of surveys within the diagnosis stage, a general survey or a detailed survey. This is an artificial separation, because diagnosis work is a continuum in terms of the depth and detail involved in the investigation. However, the concept of two levels is useful when considering the purposes of the initial investigation and the work that is likely to flow from the initial recommendations. Further detail Appendix 2: Timber rot and moulds 2.1 The diagnosis process The diagnosis process follows an investigative methodology as shown in Figure 8. It is a logical and ongoing process, designed to cause the minimum amount of damage to the building while at the same time providing a reasonable overall understanding of the likely causes of leaks and extent of damage. Initial assumptions can change as further information is gathered and assessed. An open mind is needed in order to avoid drawing premature conclusions. 16 WEATHERTIGHTNESS remediation

19 Figure 7: The diagnosis stage The building Building type Height Wall claddings Windows/doors Roof design Decks Risky features Maintenance The owner Nature of ownership Common/individual spaces Maintenance responsibility Property values Sales history Other reports Reason for seeking advice Possible motivations Relevant lifestyle bits General information Visual inspection Council records Local knowledge Owner/manager Manufacturers (refer to Section 1) The site Location Wind zone Prevailing rain/wind Rain/wind direction when leaking Local shelter Slope Sunshine/shade Accessibility No known problems (no obvious current leaks) Construction history Drawings/specifications Inspection records Other inspection reports Producer statements Warranties Technical information Invoices (eg, timber) Past repair work Weathertightness risk E2/AS1 risk matrix Identify risky locations Reasons for evaluation? Known problems Signs of potential problems Code compliance issues Similarity to problem buildings Seeking peace of mind Known problems (obvious current leaks) Section 2: Diagnosis stage General survey Visual examination Review documents Moisture testing Exploratory cut-outs Identify defects Assess durability Assess Code compliance Recommendations (on next steps) evidence of moisture (or significant defects) A general survey for a determination under the Act is a compliance issue and a detailed survey is needed before advising on repairs. Detailed survey Visual assessment Moisture testing Sample cut-outs Leak sources/paths Sample testing Other techniques Extent of damage Scope of repair work (and early estimates) WEATHERTIGHTNESS remediation 17

20 Figure 8: The diagnosis process (Note: summary only refer to text for detail) Step 1: Visual investigation Further information supplied by the owner/occupants Assessment of weathertightness risk factors Visual inspection of building Step 2: Non-invasive testing Moisture meter in capacitance mode Visual signs of moisture Smells of dampness (refer to Moisture meters box) Step 3: Invasive testing Drill into framing Take moisture readings with long probes (refer to Moisture meters box) Step 4: Cut-outs and samples Cut holes to explore invasive moisture testing Take further confirmatory moisture readings Test timber samples as required Step 5: Identify leak sources Use results to identify likely leak sources Carry out further tests as required The scope of the investigation A significant issue is the extent of appropriate investigation and reporting levels, dependent on the purpose and scope of the survey. While this section concentrates on detailed diagnosis, less detailed surveys with limited scopes are sometimes called for and can be useful at the initial stages for deciding which parts of the building to survey in more detail and how invasive that survey needs to be (refer to A limited scope survey ). Often combined as one step A limited scope survey In a less detailed general survey, limited invasive moisture testing may be the extent of the inspection process necessary to fulfil the particular purposes of the evaluation. (However, several sample cut-outs may be carried out to determine underlying construction details at critical junctions such as window jamb to sill junctions and inter-storey junctions.) 2.2 Steps in the diagnosis process The diagnosis process in Figure 8 is described as follows Step 1: visual investigation From the owner s descriptions (and the consultant s analysis of risk factors), a visual examination of the building and its condition is undertaken. This inspection provides important clues on moisture problems, and can indicate the areas that require particular attention (refer to Signs of moisture presence ). However, the fact that there are no initial obvious signs of moisture should not deter an investigation, as leaks can be extremely advanced before symptoms appear. Moisture levels in walls can build up over a long period, with occupants being unaware of any problem. There can also be multiple causes of water entry, and water can travel a long way from a point of entry before it is apparent. Areas where moisture is evident and/or damage has already occurred are usually examined first. An experienced consultant, or their specialist adviser, also aims at this point to identify the probable leak source(s). The overall standard of workmanship and current maintenance can also indicate potential moisturerelated problems. Other moisture sources It is important that the survey includes an assessment of subfloor areas as these may be inadequately ventilated and damp. Internal causes of moisture generation should also be noted (refer to Internal moisture ). 18 WEATHERTIGHTNESS remediation

21 Signs of moisture presence (from external or internal moisture) Stained/rotting carpet, rusty fixings Mould and mildew growth Swelling of skirtings or other trim Sagging ceiling linings Sagging or uneven floor surfaces Lifting of vinyl floors Corrosion of fixings Water dripping from soffit Dark stains, paint bubbles Paint and substrate deterioration Musty smells, nail popping Cracks type and location Efflorescence Selecting test locations Evidence from visual inspections (including highrisk areas) is used to select moisture test locations. Non-invasive testing is usually (and preferably) undertaken externally, because water accumulates or travels immediately behind the external cladding. However, there may be instances when lack of access precludes external investigations, or where the external cladding material is not suitable for surface testing, in which case less reliable internal investigations are necessary (refer to Apparently dry buildings ). Internal moisture Signs of moisture inside a house may initially appear to indicate leaks, but instead result from other problems such as leaking plumbing or condensation resulting factors such as the: lack of adequate thermal insulation, and/or lack of adequate ventilation, combined with occupants habits (eg, cooking, showering times, a house shut up during the day) Step 2: Non-invasive testing Visual observations are accompanied or followed by non-invasive moisture tests, using a moisture meter in capacitance mode. It is important to understand the limitations of capacitance mode testing (refer to Moisture meters ). The results of non-invasive testing should be compared with a known dry area that has been established as a control, with test results backed up by invasive testing and sample cut-outs at critical locations. Apparently dry buildings Visual inspections and non-invasive testing often provide no initial evidence of leaking, while further investigation can reveal signs of severe moisture penetration. If circumstances prevent the use of invasive testing (eg, for a pre-purchase inspection), then the limitations and risks involved must be explained clearly to potential users of the information. Moisture meters Moisture meters use changes in electrical properties in timber to provide an estimate of the moisture content. The two common types of meters in use are the resistance meter and the capacitance meter (which can be purchased as a single meter with two modes). Note the results from both types must be compared with known dry locations as readings may be affected by hidden materials (metals and chemical preservatives). Capacitance meters (non-invasive testing) These are used on a surface, and measure an electrical property called the dielectric constant and produce an electric field that can penetrate into the timber. Although the field can penetrate deep into the timber, the meter readings are biased to the surface moisture contents (so internal readings are frequently misleading). Resistance meters (invasive testing) These measure the flow of electricity between two pins inserted into the framing, where the timber acts as an electrical resistor between the pins. Different timber species and treatments have varying electrical resistance, so values shown on the meter will need to be adjusted to suit the species and the type of timber treatment Step 3: Invasive testing Visual observations and non-invasive moisture tests are followed by invasive moisture tests with the meter in resistance mode (refer to Moisture Meters above). Selecting test locations The evidence collected in previous steps is now used to select high-risk and other locations in the building for invasive moisture testing. WEATHERTIGHTNESS remediation 19

22 further detail Figure 3: Common areas of weathertightness risk Control point Establish equilibrium moisture levels by identifying areas likely to be dry (such as beneath eaves) to allow comparisons with other readings. Material from drillings Clues on timber condition can sometimes be gained from evaluating the timber extracted by drilling: dampness of timber and cladding softness and colour/consistency of drillings. Dry but decayed There can sometimes be areas of substantial decay without elevated moisture readings or obvious signs of decay. Examination and testing of drillings and/or cut-outs is needed to reveal the decay in this type of situation. further detail Appendix 2: Timber rot and moulds When the general level of elevated moisture levels is established, further invasive testing is needed to provide the likely sources of water entry, associated leak lines, areas of damage and points where water escapes to the outside. The aim here is to provide an overall picture of the moisture behaviour within walls. Invasive moisture readings are easiest to follow if they are presented on a photograph or elevation as shown in Figure 9. This is referred to as moisture mapping Step 4: cut-outs and sampling This involves cutting out sections of cladding at selected locations to confirm leak paths, causes and decay. It also allows samples of materials to be extracted and analysed for identification of timber treatment, decay and moulds (refer to Timber samples ). Although cut-outs can help to establish likely leak paths, the full extent of leaks will only be confirmed as areas of cladding are removed during repair work. Where weathertightness defects are suspected, cut-outs may also be used to expose underlying components (for instance, a hidden inter-storey junction). figure 9: moisture readings Note: a table identifying locations and descriptions may be added for further clarification. Control moisture reading (below eaves) Example house 24% Moisture readings 12% Cladding cut-outs (to determine underlying components and/or condition of timber) 24% 36% 16% 22% 40% 16% 24% 40% 35% 14% 14% 15% 24% 16% 27% 40% 15% 15% 20 WEATHERTIGHTNESS REmEdIATIoN

23 Repairing cut-outs Consider how cut-outs will be temporarily or permanently weatherproofed once testing is complete (including using the assistance of a builder if necessary). If problems are revealed, permanent repair may wait for the later remedial work. Timber samples Samples for laboratory testing should be taken from exposed timber. Samples should be chosen according to the: dampness of timber and cladding softness and colour/consistency suspected decay during construction suspected past/present leaks. Special drilling tools (incremental borers) are available to take timber samples Step 5: Identify leak sources At this stage, evidence collected in the previous steps is used to help identify the reasons for moisture entry, the possible extent of timber damage, the likely leak paths, the initial sources and any other contributing defects (refer to Contributing defects ). Further checking and sample testing may be needed at this point in order to reach reliable conclusions, and the consultant should be prepared to revisit and test earlier assumptions. Contributing defects Leaks can be complex. While a leak may be tracked to its source, other weathertightness defects commonly contribute to the extent of moisture penetration (and consequent damage). All possible sources must therefore be checked. Examples are a: leaking parapet cap at the top of a wall, which has a horizontal junction further down that does not allow water to drain leaking window jamb above a non-draining sill. Figure 10 shows how likely leak paths may be presented. This type of presentation may be repeated for all applicable elevations. figure 10: leak sources leak sources A Inadequate jamb seal at face-fixed windows b Poorly weatherproofed balustrade/ wall junction c Corner of uncapped flat top to monolithic balustrade d Lack of kickout to bottom of apron flashing Note: additional cut-outs are likely to be made to confirm conclusions. contributing defects E No sill drainage f No drainage at horizontal joint (moisture trapped) G Cladding too close/ buried in ground, or no anti-capillary gap C B D F D A E Example house Initial cut-outs (refer note) G Moisture eventually spreads along bottom plates WEATHERTIGHTNESS REmEdIATIoN 21

24 2.3 diagnosis conclusions damage assessment Figure 11 shows how the assessed likely extent of timber decay and damage may be illustrated. Although this section focuses on identifying moisture entry and damage, investigations are likely to identify weathertightness defects that have not yet caused leaks or damage. Assessment should therefore include predicting likely further damage if repair work is not undertaken (refer to Future risks ). Structural concerns If there is any concern regarding the effects of timber decay on critical structural components, engineering advice must be sought and temporary measures taken to ensure safety. Diagnosing mould and decay The decay specialist Ensure the testing is carried out by a recognised specialist in the field, as mould and timber analyses can involve different expertise. In particular, timber analysis requires more specialised knowledge than plant pathology or mycology. Identification of the degree of timber decay and the type of moulds that may be present on framing, wraps and linings is a specialist task that requires laboratory testing. Samples of moulds and suspected timber decay should be taken for laboratory analysis. Further detail Appendix 2: Timber rot and moulds Future risks In certain situations, decisions will be needed as to whether defects that are not yet leaking are likely to allow future moisture entry if they are not upgraded. (The extent of timber treatment is critical for assessing possible consequences). Further detail Section 3.5: Repair priorities Identifying and repairing causes of leaks The diagnosis now needs to provide a prognosis for the building envelope and to outline recommendations for repair. In order to forecast weathertightness and durability performance, the extent of damage and deterioration must be quantified, based on the level of any timber treatment and the assessment of damage discussed in above (refer to Initial options for repairs ). Figure 11: Likely extent of timber decay and damage Estimated extent of current timber damage (based on limited destructive sampling) Note: additional cut-outs are likely to be made to confirm conclusions. Example house Initial cut-outs (refer note) 22 WEATHERTIGHTNESS remediation

25 The work required to repair damage and to make the building weathertight and durable must address both the symptoms of damage and the mechanisms of deterioration. Further detail Section 3.2: Current state of active defects 2.4 Reporting The level of reporting that is required depends on the objectives of the survey, and should be tailored according to the circumstances. A detailed survey will usually result in a detailed report, while general surveys are limited in scope and will lead to less detailed reports. Initial options for repairs Alternative remediation strategies are considered in detail during the design stage. However, initial options still need to be explored in order to provide an earlier outline scope of work for the remediation project. In broad terms, these options fall into three categories. Complete re-cladding of the building Targeted repairs Combination of re-cladding and targeted repairs costs At the completion of the diagnosis work, the potential extent and likely severity of problems are known and broad approaches to repair have been identified. Although limited information is available, initial estimates must be prepared to allow project budgets to be established so that decisions can be made about the next steps in the remediation process (refer to Initial repair estimates ). Further detail Figure 7: The diagnosis stage Recommendations Whether general or detailed, the survey report needs to cover the specific brief, information collected, investigations undertaken, and results of those investigations. For a general survey, the recommendations would usually be at a broad advisory level, and could include the requirement for a detailed survey of the building. The report that results from a detailed survey will not only include further detail, but also often be extended to cover a recommended scope of repairs and, most usefully, a preliminary estimate of cost for the remedial work. However, it must be noted that the estimates will be based on experience with similar, completed repair work (therefore limiting the accuracy). The design work is yet to be done, and the full extent of the damage is yet to be revealed. Further detail Section 3.9.2: Estimates and budgets Initial repair estimates Allow for: all project costs including design, administration and consent fees etc (not just repair costs) upgrading where necessary to comply with the Building Code costs related to timing and disruption issues (including alternative accommodation if needed) remedial work to prevent potential damage. WEATHERTIGHTNESS remediation 23

26 3 Design stage Figure 12 summarises the overall design process that is considered and explored in this section. 3.1 Introduction Remediation work uses the results of the diagnosis process described in Section 2 to develop a detailed remediation proposal ready for tendering (refer to Starting point of design ). In simple situations, little further development will be needed, but in many cases the initial scope of work forms the beginning of a complex process of exploring options and priorities of repair work (to be discussed with the owner). Detailed design proposals can then be prepared for contracting and construction of the remedial work. Starting point of design At the start of design development, the consultant should have the following. Descriptions of known current defects Estimated extent of moisture penetration and deterioration Recommendations that provide a general outline of repair work Rough orders of cost for the scope of work Interpreting diagnosis results The consultant needs to interpret the diagnosis results to appreciate the significance of the underlying defects and risks. Further recommendations should be considered, as what might appear to be the most obvious methods of repair may not be the most appropriate (given the complexities commonly involved in moisture problems). How does a defect allow water in? It is important to understand this. The way a defect triggers leaks can be unexpected, depending on particular circumstances such as siting, orientation, construction, maintenance etc. Also, combinations of defects can work together, so fixing one defect may mean that others resurface later. As well as quantifying the extent and severity of deterioration, any defects that have caused (or contributed toward) moisture damage should be identified in order to allow future risks to be evaluated (refer to How does a defect allow water in? ). Active and inactive defects Weathertightness defects have been separated in this section into two types, active and inactive. Active defects refer to those that are leaking at the time the assessment is undertaken (referred to as currently leaking). In contrast, inactive defects are those not currently associated with elevated moisture levels or damage in the adjacent timber framing, although (depending on the circumstances) they may have leaked in the past or have potential to leak. Both types of defects are important when considering repair priorities. Further detail Section 3.5: Repair priorities 3.2 current state of active defects The most important defects are those that are currently leaking and these need to be considered carefully, in terms of their locations and type. General types Active defects should be grouped into broad types so the nature and common characteristics of each type can be further considered (refer to Grouping defects ). Grouping defects An example of grouping could be: within the cladding itself windows and doors parapets roof junctions apron flashings decks and balustrades penetrations. Further detail Figure 3: Common areas of weathertightness risk Table 5: Common weathertightness defects 24 WEATHERTIGHTNESS remediation

27 Figure 12: The design process General survey For signs of current or potential leaks Leaks? No Defects? Low risk Maintenance Identify risk areas Specify maintenance Consult client (explain risks) No work currently needed Low priority Unlikely to leak Low consequence Other issues Other compliance issues Programming of work Town planning issues BCA requirements Occupation during work Future maintenance Visual impacts Longterm durability Property value Cost-effectiveness Value decreased Value increased Value maintained Diagnosis stage Refer to sections 1 and 2 Yes: moisture evident (Start of design stage) Yes: future risks Weathertightness Durability (high-risk areas) No Isolated Not repeated? Discrete repair? Advisable Pro s and con s Staging Defects requiring more detailed survey work Higher risk Inactive Currently dry Other defects? Durability? Risk for future? Need for work? Future risks Mitigating factors Aggravating factors Work needed? Limited Other locations? General repair? Limited repair? Urgent Likely to leak soon Has leaked in past Organise temporary repairs and structural support to prevent further deterioration and to ensure safety Consult client (choose strategy) Detailed survey To establish likely: Leaks and paths Timber treatment Decay and damage Future risks Initial scope of work Current state of defects Active Repairs Other options? Classify locations Classify types Characteristics? Nature/extent Details repeated? Similar locations? Cladding general? Component general? Limited/isolated? Yes Nature of defects Systemic Degree of damage Recladding? Other options? Importance of remediation Risks vs consequences (Table 2) Repair priority Critical Temporary repairs Safety Remediation priorities Sketch options Options for reducing risks Developed design options Alternative strategies Preliminary cost estimates Develop design Sketch design Contract documents Final cost estimates Further investigation needed DESIGN SET PRIORITIES RISK ANALYSIS DIAGNOSIS WEATHERTIGHTNESS remediation 25

28 Specific locations The specific locations of identified active defects in the building should be studied, and their particular characteristics identified (eg, exposure, risk features etc). Consider early options Consultants should develop preliminary solutions for known active defects, and options for achieving the same objective should be explored. Consideration should be given to various repairs in terms of costs, required maintenance and expected durability (refer to Initial sketch details ). Initial sketch details Initial sketch details will be rough and exploratory as the first translation of descriptions into 3D forms. However, they should still allow the assumptions used in the earlier preliminary estimates to be checked. Problems are also more likely to be identified when sketch details are explored Systemic defects If defects are systemic throughout the building, the resulting remedial work is likely to be extensive. If the problem has led to moisture penetration, mould and decay may be established. In these instances, complete re-cladding of the building is likely to be necessary, along with extensive replacement of decayed timber framing and the installation of increased levels of weathertightness protection (such as cavities) to provide a future dry environment within walls. However, some defects can take time for the building element to deteriorate sufficiently to cause extensive problems. Less drastic remedies could be appropriate in these circumstances. In all cases, the level of existing timber treatment will be a critical factor in determining the likely consequences of leaking. 3.3 Nature of active defects The initial consideration of defects described above helps in understanding the defect mechanisms applying to a particular building, and helps to clarify remedial recommendations and options (refer to The nature of defects ). The nature of defects To help consider options for repair, it is useful to classify defects into categories as follows. Systemic problems Limited problems Isolated problems The decision of whether defects are isolated, limited or systemic is critical for establishing the appropriate repairs, and raises issues of future moisture problems, including potential moisture problems for wall areas that are currently dry. Figure 13 shows how (depending on the particular circumstances) defects might be categorised. Further detail Table 1: Risk of leaks and consequences of failure Nature of defects Decide whether defects are systemic, limited or isolated, by considering whether there are: general cladding problems such as lack of control joints, sub-standard plaster etc. general component or location problems (eg, window flashings, base details, clearances, roof wall junctions repeated generally around the building) other areas with similar defective details similar locations/exposures isolated problems with limited application further investigations needed to confirm how widespread defects are. Current condition At this point, further investigation could be necessary to reliably establish the extent of present timber damage. This may require additional survey work and laboratory testing. Further detail Appendix 2: Timber rot and moulds 26 WEATHERTIGHTNESS remediation

29 figure 13: The nature of defects Examples of defect categories are: A Systemic Sub-standard solid plaster stucco or textured coating EIFS or flush-finish fibre cement defective backing sheets or joints Lack of or poor control joints Extensive cracking Inadequate weathergrooves or overlaps to weatherboards b limited Poor window flashings Cladding clearances Apron flashings Intercladding junctions Corner junctions c Isolated Deck-to-wall junctions Meterbox sealing Garage door head Curved-top window head Pergola fixings Ground clearances Skylight flashings Pipe/cable penetrations Note: The list is intended to be an example of one possible division only as categorisation is based on judgement of the particular circumstances and the result will vary accordingly. c c A c c c b b b A b b b c c c c b A Need for re-cladding Once current moisture penetration and deterioration is known, the next question is whether all walls need re-cladding or just limited areas. An important influence will be the level of timber treatment and other component problems noted during inspections. It is likely that a systemic problem, together with a component problem (for instance, lack of control joints leading to cracking, combined with poorly flashed windows), will lead to re-cladding being the most cost-effective current or future solution. Currently dry walls If some walls are dry and undamaged, the consultant should investigate why this is in order to assess the risks of future moisture penetration. It may be that local protection (for instance, by roof overhangs) has delayed the onset of leaks and a defect may be remedied in time without the existing cladding having to be removed. In other cases, limited repairs may not be possible (refer to Dry but systemic defects ). Dry but systemic defects Some types of systemic defects cannot be remedied without recladding. A building may be currently dry on all walls, and yet require recladding in order to comply with the durability provisions of the Code. Two examples of this are sub-standard solid plaster and inadequate backing sheets (eg, layout, material, thickness) behind flush finishes. These types of defects may not yet be causing leaks, but are considered likely to deteriorate and leak in the future (based on experience of similar situations). WEATHERTIGHTNESS REmEdIATIoN 27

30 Other options for currently dry walls At this stage, consultants should explore the options available for protecting dry walls despite the identified inactive defect(s). If moisture can be deflected away from the wall, the dry condition may then be extended. Further detail Table 2: Reducing the risks limited defects This category applies to those defects that are limited to discrete components or locations around the building. The problems identified during the diagnosis phase need to be put into the context of the specific building (refer to Limited defects ). Component problems These are associated with particular components (such as repeated defective window installations). Location problems Common problems include areas such as cladding clearances, the bottom of apron flashings, roof to wall junctions, and some types of cladding base details. Limited defects Consider the following. Are there other general problems? Are other cladding details generally okay? Are there other similar defects/locations? If so, have they remained dry? Does further moisture testing need to be done on apparently dry walls? If dry, why have they remained dry? Will they remain dry in future and for how long? Isolated defects This category applies to isolated features of a building, such as decks, pergolas, special windows, chimney structures and the like. It may also apply to certain locations that do not apply elsewhere around the building (such as a limited section of wall). Depending on their position within the building envelope, isolated defects are generally more amenable to targeted repairs (refer to Position of isolated problems ). Position of isolated problems The extent of damage associated with isolated problems depends on where that particular feature is located within the building. For example, a leaking deck-to-wall junction will have substantially greater impact on the surrounding wall for an upper floor deck (particularly if above living areas) than for a ground floor deck with a concrete foundation wall below it. Similarly, defective wall-to-roof junctions of a dormer window will have greater consequences than defects in a curved-top ground floor window. As is done with the other categories, a consultant will need to confirm that the particular defect is not repeated in locations elsewhere in the building. If it is, moisture levels and possible damage in those areas will need to be checked. 3.4 Potential for future damage The likelihood of future deterioration is as important as current deterioration. Even if walls are currently dry, possible future problems must still be assessed to determine whether there is a reasonable expectation that the cladding (in its present form) will continue to keep the building dry (refer to Judgement ). It is important that consultants establish the potential for future moisture problems, because this will shape the timing, nature and eventual costs of the remediation measures that are required. Judgement It is critical that consultants use their own knowledge and experience to infer known weathertightness problems, for example, from both: the particular building construction details site conditions other buildings similar details, claddings, risk features and so on similar site conditions. Further detail Section 1: General information collection stage 28 WEATHERTIGHTNESS remediation

31 Past and future maintenance The level and quality of past maintenance may have impacted on the current condition of the building, but maintenance can be increased to possibly improve its weathertightness and assist in its future performance. Hidden leaks and decay Be aware that not all leaks or decay may have been identified in a survey and walls that appear to be dry often have hidden moisture or decay problems. The following scenarios use two buildings, one that seems to be leaking on some walls only, and one that is apparently dry building leaking on some walls It is important to understand why the same type of defects that are causing moisture problems on some walls, have not yet leaked onto other walls (refer to Why are some walls not leaking ). This understanding will help establish whether: mechanisms that are acting to deteriorate parts of the building will begin to do so on undamaged parts in the future (ie, inactive defects will become active) other mechanisms are in place that could cause problems or prevent problems the rate at which damage has occurred on leaking walls is likely to escalate. Why are some walls not leaking? Consider mitigating influences together with factors applying to dry areas such as: prevailing weather rain, wind, sun site protection site shelter from trees, slope, and other site features building protection (eg, eaves, canopies) variable workmanship ease of maintenance and inspection current maintenance has this prevented problems to date? length of time walls have stayed dry risks of undetected leaks in future possible future movement in framing, and likely effects Apparently dry building Building owners are becoming increasingly aware of the type of buildings and claddings that have in the past experienced moisture penetration and may be concerned about the condition of their building, regardless of any known moisture problems. A general survey allows a consultant to prepare recommendations (including priorities, or the need for further investigation) to allow an owner to decide on (if any) repair work, maintenance, ongoing monitoring or further investigation should be undertaken (refer to Aims of general surveys ). If the results of a limited survey provide reasonable assurance that a building is currently dry and undamaged, the process followed from then on will be similar to that used for maintaining dry walls on a building that has some leaking walls. However, if the survey indicates a likelihood of significant moisture penetration and damage, a more detailed survey will be needed. Aims of general surveys The key aims of general surveys are to: verify current moisture levels using appropriate invasive moisture testing of locations in areas considered high risk identify high-risk areas and consider the detailing used in these locations, cutting out small sections of cladding at sample positions (such as a typical jambto-sill junction, inter-storey junctions etc) to establish likelihood of back flashings at high-risk junctions identify weathertightness defects that are likely to lead to future moisture problems, including mitigating influences such as shelter and drainage. The discovery of moisture penetration should lead to a subsequent detailed diagnosis. Limitations of general surveys General surveys may be used for apparently dry buildings, or in cases where the weathertightness compliance of a building is in doubt (such as for buildings referred to the Department for a determination). An inspection process should be used in general surveys that provides sufficient evidence (when considered with information collected) WEATHERTIGHTNESS remediation 29

32 to allow assessment of the ongoing weathertightness of the cladding systems. These inspections are less detailed than those usually undertaken on obviously leaking buildings, but still involve invasive moisture testing, sample cut-outs to inspect underlying construction and the identification of defects that could lead to future weathertightness problems. Further detail Section 2.1: The diagnosis process 3.5 Repair priorities The preceding sections explore ways of collecting, analysing and categorising information on a building, in order to understand both the current condition and the nature of possible future risks. The following section discusses how repair priorities are established Importance of remediation While it may be ideal to remedy every identified defect in a building, a practical approach is needed to suit the particular circumstances (for instance, staging the repairs according to their priority). This involves considering the location and severity of the leaks and/or defects, with the likely consequences, keeping in mind that completed repair work must meet weathertightness and durability provisions of the Building Code. One useful approach to establishing remediation priorities is to balance the level of risk of moisture penetration against the severity of the likely consequences (including health risks), should a leak occur. Table 1 illustrates one system that could be used to achieve this. Risk analysis caution Care must be taken when analysing risks. There must be a rational, recorded basis for establishing varying risk levels that can be explained as reasonable in the circumstances of the particular building. The categories within Table 1 are shown to illustrate the use of risk profiles to suit specific situations. Decisions on the priority of the repair work required will vary according to the particular building structure (for example, the level of timber treatment) and the cost-effectiveness of the repairs Repair priority Critical work (Type A in Table 1) Critical areas require immediate action to prevent further deterioration and to ensure safety. Temporary repairs, structural work or measures to protect the health of the occupants may be needed before the main remedial work can be carried out (refer to Moulds ). Table 1: Risk of leaks and consequences of failure Likely consequences (1) Current condition Severe and widespread Moderate or isolated severe Minor and isolated Leaking and degraded A A B Some current leaking A B C Highly likely to leak B C D Leaks possible in future C D E Leaks unlikely D E E Risk/consequence levels applied to a particular project might be classified as: A Critical remedial work C Necessary remedial work E Low priority B Urgent remedial work D Advisable remedial work (1) allow for effect of timber treatment on durability (Note: A, B, C and E categories are usually straightforward, but Type D requires more analysis/consideration.) 30 WEATHERTIGHTNESS remediation

33 If timber decay could endanger critical structural elements, a structural engineer should review the condition and design any temporary propping required. Access to parts of the building may need to be restricted (for example, to decayed decks or support beams). Further repairs can also be carried out to weatherproof moisture-affected areas temporarily until permanent repairs are completed. Moulds Evidence of moulds requires immediate attention, and specialist laboratory tests are needed to confirm the type and extent, together with advice on actions required to protect the health of occupants and workers. Further detail Appendix 2: Timber rot and moulds Urgent/necessary work (Types B, C in Table 1) For all necessary remedial works, outlined design proposals should be developed to a level suitable for owner consultation, and any estimated costs should be updated. These categories include permanent remedial proposals for Type A areas (to replace temporary repairs). Advisable work (Type D in Table 1) This category requires the most consideration and judgement. The advantages of risk reduction need to be balanced against likely consequences, subject to the repaired building meeting the requirements of the Building Code (refer to Advisable remedial work ). Advisable remedial work Factors to be considered include the following. Existence and level of timber treatment Presence of active fungal growth Difficulty/costs (access, design style etc) Increase in vulnerability from cutting into an existing dry structure Whether work can be planned for later implementation without significant effect Whether any leaks would be obvious, or could remain undetected in future Whether the risks could be reduced with improved maintenance (within normal reasonable expectations) Low priority (Type E in Table 1) This category is where details have been identified that do not meet current expectations, but where the risk (and likely consequences) of moisture entry is judged to be low. In certain low and medium exposure conditions, specific combinations of exposure, wall construction, detailing and timber treatment may result in little or minimal damage, even if the wall construction is not ideal. In the unlikely event of a leak occurring, the consequences have been assessed as not likely to be severe or widespread, and comprehensive remediation may not be warranted. Code compliance The consultant must still ensure that recommended remedial work will result in an adequately weathertight, durable and Code-compliant building. The possible risks associated with some low priority defects (and the likely consequences) need to be explained to an owner, who should also be made aware of preventative ongoing maintenance they should undertake (for instance, regular washing, maintaining sealants and coatings, cleaning gutters etc) and periodic monitoring of these areas. Having established the varying levels of importance of remedial work required for the building, the consultant should then prepare a priority list of repairs and proposals, together with a preliminary estimate of costs for those repairs and proposals Staging of remediation work At this point in the design development, the scheduling of work can be considered including the possibility of staging repairs over time (refer to Staging repairs ). Limited staging It may be possible to stagger work, starting with the most damaged or risky areas. This allows repair costs to be spread, but extends disruption and will be costlier in the long run. WEATHERTIGHTNESS remediation 31

34 Extended staging It may be possible to extend remedial work over longer periods for example, where repairs on low exposure walls are deferred for 5 to 10 years, if their condition is monitored. Building consent Discuss any proposed repair programme with the BCA to clarify implications on the building consent. The Act requires a code compliance certificate to be issued within 2 years of the consent. Unless the BCA grants an extension, separate consents will be needed if the remedial work takes too long, which will add to the overall costs. Staging repairs Possible phases Consider the following phasing of different types of the work. Immediate work to prevent further damage and ensure safety Short-term work for temporarily repaired areas, those likely to leak in the near future or with severe consequences if leaks were to occur Medium-term work to remedy defects with little immediate risk Longer-term work for areas with lower level risks and consequences, but where work is needed for longer term durability Factors to consider Primary factors to be considered include the following. Construction costs the additional start-up costs with separate stages Risk of further damage areas not repaired may continue to deteriorate Disruption occupants will be disrupted for a longer period of time by noise, access, loss of use of areas, dust and other construction irritants Financing different scenarios will require different realistic cash flow plans Property values specialist advice should be sought on the impact of varying remedial scenarios on property values Any future sale deferred work may need to be declared as an area with known potential problems. 3.6 design-related issues The next part of the guide considers in further detail some of the associated design issues that have been mentioned in preceding sections. These matters will affect decisions and may limit options in many situations Reducing risks The E2/AS1 risk matrix covers key weathertightness risk factors, and the guidance document External Moisture A guide to using the risk matrix offers useful information and explanations of these factors. Possible measures to improve weathertightness, such as those suggested in Table 2, that provide and maintain a dry environment, should be explored. These may prove more cost-effective than the installation of new cladding over a drained cavity. The effect of shelter The effect of rain on walls can be significant. Providing shelter minimises the effect of water penetration on walls. However, it is important to check timber treatment levels and current timber condition in these areas, because apparently sheltered walls may still be degrading. Remediation options aiming to preserve currently dry walls can include providing shelter to individual details or to a whole wall. Many building envelopes are not clear-cut in terms of defining the remedial work required visual effects The change in a building s appearance could be the most obvious result of any remediation work, particularly if it involves alterations to cladding materials or other noticeable elements (such as the removal of enclosed decks, or the addition of eaves, canopies or enclosures in order to reduce the risk of moisture penetration). If the remedial work aims to minimise changes to the look of the building, care should be taken to select profiles, materials and colours that complement or enhance the original design. 32 WEATHERTIGHTNESS remediation

35 Table 2: Reducing the risks E2/AS1 risk factors Associated elements Possible risk reductions Wind zone Local influences Add permanent localised shelter (1) Roof/wall intersection design Eaves width Envelope complexity Deck/balcony design Limited protection of wall Enclosed balustrades Oblique eaves Multiple claddings Pergolas Special windows (eg, box, bay, corner, raked or curved tops) Decks over living areas Decks open underneath Cantilevered deck Increase roof overhangs Change to side-fixed open balustrades (with no upstands) If rafters exposed, clad soffits Extend eaves/verge widths Add canopies to compensate for lack of eaves Replace parapets with roof overhangs Simplify or reduce inter-cladding junctions Remove or roof over Alter to freestanding type Replace with standard joinery Add canopies (1) Enclose the deck Expose underside to allow drying of joists (1) Improve access for monitoring Separately support deck (1) Take care some measures are effective only if they are retained as permanent features. However, if the work is likely to result in major changes in appearance, professional design assistance is warranted as architects and experienced designers should be skilled in understanding and managing the consequences of potential visual impacts. The visual impact of remedial measures must be considered carefully as it has the potential to positively or negatively influence the value of the building. Revising the image Most repairs will require building consents which will then form part of the public records of a particular building. It may be worth exploring the advantages of purposely revising a building s image, rather than returning it to the same external appearance as prior to the remediation work. Figure 14 shows how the appearance of a building might be changed. The combination of changes in cladding, with a decrease in risk features, can substantially alter a building s appearance in a positive manner if repairs are skilfully executed. The resulting impact on the property s value could outweigh the initial costs of undertaking the work. Improvement costs If design changes are made, itemisation of the applicable costs may be needed by the owner for future claims and/or arguments. (Check with the legal advisor if applicable.) Further detail Section 3.7: Other issues WEATHERTIGHTNESS remediation 33

36 Figure 14: Visual effects Original building no eaves parapets exposed decks solid balustrades cantilevered decks Post-remediation option extended eaves parapets replaced with verges canopy over deck open balustrades cladding changed decks supported Figure 15: Town planning issues Extend eaves? Close in deck? Replace parapets with pitched roof and eaves? Envelope restriction Add verandah? Town planning considerations It is common for buildings requiring extensive remedial work to have used the maximum building envelopes allowable in local town planning bylaws at the time of construction. If building volumes of the original design were maximised, then the addition of protective weathertightness measures to a building can conflict with building envelope restrictions, as shown in Figure 15. Envelope restrictions, repair options and possible cladding changes must be discussed with the local council early in the design process. Some councils may allow eaves and canopies to project into public space (eg, road reserves), but permission from neighbours is likely to be required for changes to other boundary areas. 3.7 other issues The following provides further detail on some of the issues mentioned in previous sections (such as cost-effectiveness, ongoing maintenance and strategies) that can affect repair decisions and may often limit remediation options. 34 WEATHERTIGHTNESS remediation

37 3.7.1 cost-effectiveness Cost-effectiveness is key to certain remediation decisions, and judgement on what is important depends on the viewpoint of those involved and the timescale involved. A measure may not be cost-effective over the short term, but could be when considered on a longer-term basis. Cost-effectiveness can be viewed differently by various stakeholders according to their financial and long-term interest in the building (refer to Cost-effectiveness viewpoints ). Alternatives may need to be developed (with costs and associated risks outlined for each) to allow owners to make informed choices. Objective recommendations Consultants must base advice to owners on the results of investigations, and not be party to any inadequate repair work (based on immediate short-term wishes). Cost-effectiveness viewpoints While all remedial work must comply with the Building Code, a consultant should be aware of (and able to counter if necessary) other viewpoints. Examples of different viewpoints include: an owner planning to sell an owner planning to remain long term a body corporate balancing wishes of the unit owners against responsibility to ensure ongoing weathertightness lending institutions financing remedial work or with mortgages over the building parties involved in the original design and construction of the building future buyers of the property consultants concerned about exposure in regard to possible future failure ongoing maintenance Ongoing maintenance for the building needs to be considered during remediation design. Normal maintenance of the building envelope increases the likelihood that elements will continue to perform over their intended service lives (and, at a minimum, fulfil the durability requirements of the Building Code). Inadequate maintenance increases the risk of degradation of the building envelope. If any existing direct-fixed cladding is left in place, then maintenance is especially important for ensuring that these walls remain weathertight. When a wall relies on sealant joints, these must be inspected regularly and repaired as necessary. Access for appropriate monitoring and maintenance is critical, and the design should provide for this. The levels of maintenance required by different components and wall claddings will vary, with some types being more forgiving than others. Consultants should therefore consider the need for a maintenance plan for the building (refer to A maintenance plan ). Further detail Section Maintenance and monitoring A maintenance plan Ideally, customised plans should be prepared that are tailored to suit the expertise of the person who will be undertaking the inspection and maintenance. For example: a homeowner may need very specific guidance on the areas to inspect, what to look out for and the resulting maintenance actions a property manager on a multi-unit complex (or an untrained resident) may need guidance in the form of maintenance schedules an experienced professional should need little guidance. The preparation of a maintenance schedule can ensure that current and future owners know what ongoing maintenance is necessary for preventing future weathertightness problems. 3.8 Alternative strategies Remediation design starts with defining requirements, and previous sections have discussed various analyses and factors that should be considered as part of the process. This can lead the consultant to consider using alternative approaches for remediation involving different levels of initial construction cost, maintenance costs and weathertightness risks (refer to The design stage ). WEATHERTIGHTNESS remediation 35

38 The design stage In remediation projects, basic design parameters of orientation, form and layout are pre-existing. The design stage is essentially one of design development. Some owners may find it hard to see the value in this stage of the process, instead wishing to focus on proceeding directly to stopping the building from leaking Sketch options Appearance If any options change the appearance of the building significantly, these should be illustrated so an owner is aware of what the visual impact will be from different choices. Sketch options need to be developed to a level suitable for owner consultation. Relative costs should also be prepared so owners can consider the proposed remediation options in an informed way Implications of alternate strategies Table 3 summarises some common remediation strategies that are used, including their impact on performance and their limitations. A remediation project can involve combinations of strategies, with the choice of strategy influencing costs and risks for future weathertightness performance. 3.9 choosing a strategy A remediation strategy should be chosen in consultation with the owner. When presenting information, the consultant should clearly identify any issues and provide advice on them. The consultant should explain the varying levels of risk associated with repair alternatives and guide owners so that risks, costs, cash flow, appearance, durability, disruption (including costs of relocation, if necessary) and other factors are balanced. Implications on future maintenance needs, and any deferred remedial work should also be presented to the owner (refer to Approval time ). The remediation strategy or plan should reflect the integration of all repair requirements for the building; it should establish priorities and describe alternative approaches while still ensuring the minimum requirements of the Building Code are met. Approval time Owners may need considerable time to review and consider their position, particularly if the required remediation is extensive and costly. The time required for a multi-unit complex will vary according to the number of owners involved, and a body corporate is likely to need time to formulate special resolutions and payment schedules. The availability of finance may need to be investigated before choices can be made. While it is important that the owners do not make commitments without knowing that finance will be available, raising funds is timeconsuming and can delay the remediation process Project programming Different remediation strategies involve different timescales, and it is important that these are explained to the owner. Once a strategy is chosen, the consultant should prepare an outline project schedule that shows the main activities in both the pre-construction and construction phases. This is useful for owners, as it provides them with key decision dates and a timeline on what funds will need to be raised (refer to Outline programme ). While details will become more certain as the project develops, an outline programme is important in setting out the steps and general timescales involved. Owners should understand that some flexibility is needed as some parts of remediation work cannot be reliably predicted until the cladding is removed. Outline programme This shows the time needed for all stages of the project including: preparation of drawings and specifications obtaining of building consents selecting suitable building contractors obtaining contract prices completing contract formalities undertaking construction work. If the building is to remain occupied during construction work, the programme will need to allow for this. Inconvenience or health and safety issues may require occupants to vacate all or parts of the building at particular times, with the work phased to suit. 36 WEATHERTIGHTNESS remediation

39 Table 3: Implications of alternative measures Weathertightness Details Walls Town planning Code and BCA involvement Remediation measures Reduce exposure Repair damage Eliminate details Improve details Change construction Improve existing None Limited Significant None Limited Significant Effectiveness Add roof/enclose space Add eaves etc Add canopy Replace clad barriers with rails Reduces exposure Can reduce repair need Can protect some elements and junctions below Can protect existing windows and deck junctions Allows decks to drain freely Deletes leaking/risky areas Install balustrade cappings Protects vulnerable tops Replace parapets Eliminates leaking/risky areas Install parapet cappings Protects vulnerable tops Reclad over cavity To provide a reliable dry wall environment Different cladding Replace with less risky cladding Remove/reflash windows When window flashings are missing or faulty Rebuild saddle junctions To improve junction Replace sealant maintenance only Add coating maintenance only To extend current weathertight condition To extend current weathertight condition Estimates and budgets The chances of finding unanticipated conditions are higher when the full extent of the damage is not apparent until the building is opened up during construction. Carefully prepared estimates, with appropriate contingency and provisional allowances, can help to cater for this uncertainty (refer to Quantifiable/non-quantifiable elements ). Some costs can be well defined and estimated reliably once the remediation design is complete, but those associated with timber decay and damage are difficult to estimate accurately until the framing is exposed. These costs are covered by provisional allowances that are used for reimbursing materials and labour costs. WEATHERTIGHTNESS remediation 37

40 Further detail Section 4.3.4: Contract payments Time and cost overruns Because of the nature of remedial work, unforeseen situations (including original, non-compliant work) often occur, and are discovered only when cladding is removed. This can result in delays and extra costs. Over- or under-estimating Understating costs can result in owners committing themselves to a remediation project they cannot pay for. Over-estimating, however, can result in owners delaying or not proceeding with necessary repairs. Quantifiable/non-quantifiable elements Tenders will be a combination of lump sums and provisional allowances, depending on the nature of the items and work involved. Lump sums can be set for quantifiable elements such as: project specific requirements, scaffolding etc cladding removal window removal and reinstallation installation of a new cladding system replacement of interior floor coverings replacement of interior fittings. Provisional allowances (based on estimated quantities) are likely to be needed for such items as: timber replacement interior lining repair and replacement work required to services original substandard work revealed other unforeseen conditions. Project budgets All costs need to be included within the remediation project budget including associated fees, relocation and storage costs for occupants, security, insurances and so on. As well as unanticipated conditions, cost and time overruns can result from unrealistic expectations and inadequate budgets. It is essential for the owner that the consultant creates a realistic project budget that accurately reflects probable costs. Consultants must also advise owners of the level of uncertainty applicable to cost estimates at each stage of the design process, and explain to owners how the estimate plus contingency combine to give a worst case cost estimate for the project. (refer to Contingency funds ). Table 4 illustrates how an overall project budget can vary over the course of the remediation process. Contingency funds An owners contingency fund for unforeseen or unexpected problems should be included in a project budget. The amount should reflect the high side of the accuracy range at each stage of the remediation process, and, by doing so, will therefore reduce from the earliest diagnosis stage to the tender stage. For example (depending on the particular project), at the condition assessment stage, the contingency fund may be 50 percent, at preliminary design stage 30 percent, at contract documentation stage 25 percent and during construction it may be 20 percent developing the sketch design The selected remediation strategy should now be developed as necessary to allow a preliminary assessment of costs to be prepared. This step may sometimes be omitted if the earlier design work has been developed sufficiently to allow reliable estimates to be prepared (depending on project size and complexity). While work on simpler, detached house projects can probably proceed directly to the preparation of working drawings, further design work is likely to be needed for complex, multi-unit developments. This can improve the reliability of the project estimate (over those drawings used when alternative strategies were explored and presented to the client). 38 WEATHERTIGHTNESS remediation

41 Table 4 : Project budgets over time Progression through the stages of the remediation process Completion of diagnosis stage Remediation strategy selected Completion of contract documents Construction Level of information Extent/severity known Outline scope of work More detailed design Strategy chosen Phasing identified Working drawings Specification (consent documents) Tender/quote (or estimate) accepted Other issues identified Basis of estimates Historic from previous similar projects Sketch proposals available for estimating Full details available Based on accepted bid (with contingency) Expected accuracy Owner s contingency could be plus or minus 50 percent Owner s contingency could be plus or minus 30 percent Owner s contingency could be plus or minus 25 percent Accuracy should improve (say 20 percent contingency) Usefulness Shows overall magnitude Allows decisions on next steps to take Allows finance to be sought Allows finance to be secured Can plan cash flow Monitor during construction to avoid surprises Building consent authority requirements If these have not been done earlier, discussions with the local BCA or council should take place regarding building consent requirements, the level of BCA inspections that will be needed during construction, any quality assurance requirements, Code compliance or other issues relevant to the project (refer to Compliance issues ). Compliance issues Issues to consider for a remediation project include plans/requirements for: building/resource consents planned staging of work alternative solutions or E2/AS1 details quality assurance requirements variations to consent drawings minor repair work any upgrading needed for other current Code requirements (eg, fire) other Code clause issues health and safety issues (including the disposal of hazardous wastes) contract documentation At this stage of the process, the remediation strategy and proposed design will have been agreed upon and the cost estimates updated. The next step is the preparation of working drawings that, together with specification and pricing information, will form the contract documents (refer to Contract documents ). The following section considers the development of working drawings and the technical specifications. Other (non-technical) documentation required for a contract is discussed as part of the construction stage. Further detail Section 4: Contracts and construction stage WEATHERTIGHTNESS remediation 39

42 Contract documents The contract documents consist of the legal agreement between the owner and contractor (usually a standard format), together with the following documents. The building consent documents Scope of the works Working drawings Specifications Other BCA requirements Other information Pricing information. (provisional allowance, sums etc) Any notices to tenderers issued General drawings These outline the site plan, floor plans, elevations and sections, and should: indicate the overall scope of the work show interfaces between remedial work and existing unchanged areas identify locations of components reference drawings of details. Detail drawings These should detail the: locations of materials and components relationship to adjacent construction profiles of existing components clear delineation of existing versus new construction and details Working drawings Although the working drawings form part of the submission for a building consent, their primary function is to provide enough information to allow the contractor to perform the repair work in accordance with the contract requirements and the Building Code. The drawings must identify and locate all materials, components and assemblies that require repair and indicate the extent of the necessary work. Further detailed information is provided in the specifications (refer to Detail drawings ). While changing design decisions can impact on construction costs, it may be necessary to reassess some earlier decisions if new issues arise during detailing (this may also be necessary during construction, as unexpected conditions are exposed). Further detail Section 4.4.3: Contract changes and uncertainties The design of details Remediation work is obviously limited by the existing construction, many repair details may vary from those included in E2/AS1. However, the Acceptable Solution can provide guidance and benchmarking of expected performance. The weathertightness principles underpinning E2/AS1 provide a good starting point for designing remediation details to suit the particular circumstances (refer to Details ). Further detail External moisture An introduction to weathertightness design principles A BCA will need to be satisfied that the proposed repair details are Code compliant. A designer must justify the weathertightness of proposals when they are developed into construction drawings and included in the building consent application. Details This guide is primarily intended to be a guide to the process involved in remediation projects, and does not provide prescriptive solutions for repair. 40 WEATHERTIGHTNESS remediation

43 Effects on other requirements If direct-fixed claddings are to be replaced with a cavitybased system, bracing, insulation values, acoustics and fire-ratings are likely to be affected. Any changes must be catered for within the new construction details. Most repair details need to be designed to suit the specific circumstances of the building, but the principles underlying E2/AS1 should still be followed. There is little point in following a detail that was used in the original construction, when a lack of performance has been demonstrated (always remember that a dry environment must be created). Good Practice Guides Current BRANZ Ltd Good Practice Guides should be consulted for detailed information and practical advice on appropriate details (many are alternative solutions). Some guides list defects, causes and repairs, which can be useful for diagnosing and detailing remedial work Technical specifications Technical specifications complement working drawings and provide details about the quality of materials and components, compliance with standards, workmanship and any approved suppliers of materials or components. As for other construction work, documentation for remedial projects should be specific to the remediation work rather than relying on general specifications. Other general (non-technical) aspects of tender documents and contracts are discussed in the following section. Further detail Section 4: Contracts and construction stage Manufacturer s information Consultants should ensure that the most up-to-date manufacturer s recommendations are followed during the installation of components or cladding. The manufacturer should also be consulted for advice on maintaining and prolonging the durability of existing claddings or components. Upgrading existing work Sometimes, existing construction has inadequate fire ratings and bracing. This is often not apparent until revealed during remedial work. If obvious before then, upgrading these elements should be included as part of the contract documentation, with specialist advice obtained as necessary. WEATHERTIGHTNESS remediation 41

44 4 Contracts and construction stage Figure 16 shows the general contract and construction process explored in this stage, and the following stage (post-construction). This section outlines how an appropriate remediation contract is arrived at, and discusses some of the major issues to be considered during construction work. Appropriate expertise If owners manage this stage of the work, they need a similar level of knowledge and judgement as an experienced consultant in order to assure a successful completion of repair work. As discussed in the introduction to this guide, remediation projects generally involve complex technical and contractual issues that are beyond the skills and experience of most building owners (and also inexperienced consultants and builders). This section is therefore based on continued consultant involvement throughout the tendering and construction stage, in order to establish as much certainty as possible in the often complex contractual and technical processes involved (refer to Appropriate expertise ). 4.1 Tender type The type of tender suitable for the remediation project should be discussed with the owner and resolved at an early stage in the process. It is important that the owner understands the basic differences between types of tenders. Which tender is the most appropriate will be influenced by the size, complexity and location of the project. In some areas, the availability of experienced contractors may limit the choice of tender (refer to Types of tender ). The ability of contractors to interpret and manage the contract is also a factor in choosing the type of tender. Some building companies are unfamiliar with remediation work and can require additional remediation guidance from the consultant during construction. The increased fees of the consultant may then outweigh the additional cost of a more experienced builder. Selected or negotiated tenders While open tendering may be appropriate for many new buildings, most remediation projects require contractors who have special skills and experience. Limiting tenders to a group of known, reliable and experienced contractors, or negotiating with a single suitable contractor, is more likely to ensure a successful project outcome. Types of tender The owner should be made aware of the risks and benefits that apply to different types of tender. Open to all tenderers Limited to selected tenderers Negotiated with single tenderers Open tenders are generally unsuitable for remediation projects, and the reasons for recommending a particular type should be clearly explained to the owner. The consultant should also explain provisional sum items included (and how risks within a contract are allocated between the parties). 4.2 The tender documents The following section continues from Section : Technical specifications and covers the additional (non-technical) aspects of contract documents (refer to Tender documents ) General conditions of contract The general conditions of contract should be based on a recognised standard form (such as NZS 3910, those from engineers or architects professional bodies, or from other respected sources). The general conditions of contract must work with and complement the specific (special) conditions for the remediation project. It is important that any contradictions between general and special conditions are avoided, as these can lead to contractual problems and additional costs. 42 WEATHERTIGHTNESS remediation

45 Figure 16: Contracts, construction and beyond Construction documents Working drawings Technical specifications Pricing information (sums, allowances etc.) Building consent Scope of works Construction documents Other BCA requirements (eg, QA schedule) May use to invite registrations of interest (suitable for larger remediation projects) Administration First meeting (Contractor/consultant/ owner pre-construction) Introductions Communications Programming Payment processes Resolution processes Subs and suppliers Procedural issues Other concerns Site meetings (Contractor/consultant/ subcontractors/suppliers) Progress Quality issues Costs, overall budget Construction activity Design clarification Discrepancies BCA issues Variations/changes Health and safety Owner s concerns Other issues Final meeting (Contractor/consultant/ owner post-construction) As-built drawings Warranties Other information Open (open to all bids) To include minimum durability compliance (but may choose to go beyond B2 minimum) Often recommended Consult client Type of tender Occupancy Insurances Site conditions Consultant roles Tender documents Legal contract agreement Tender bid document General conditions Special conditions, P&G Construction documents Building consent items Tender type Selected (limited to known, experienced bidders) Tender(s) The contract Tender documents consultant to the contract Review Payments Progress payments - payment schedule Variation payments - lump sums - unit rates - materials plus labour Monitoring costs Work completion (Practical completion) Final inspections Code compliance items May be reoccupied Project completion (Actual contract completion) Outstanding items complete As-built drawings Code compliance certificate Defects retentions/liability Ongoing performance Maintenance Replacement/repair Negotiated (negotiated with single experienced contractor) General Quality assurance Regular inspections Variations - existing construction - client initiated - uncertain items Monitoring costs BCA inspections Special conditions (and P&G) Owner occupancy Insurances Progress payments Variations, retentions Protection requirements Space, storage, access Hours, security, facilities Services, rubbish, noise Complementary General conditions NZS 3910, IPENZ, NZIA or similar Review rates, prices etc Consult client Discuss bid conditions Recommend bid Get approval of bid Client liaison Progress update Payment approval Budget forecasts Maintenance plan Particular components: inspection maintenance frequency Renewals plan Particular components: type of renewal maintenance expected durability warranty expiries POST-CONSTRUCTION CONSTRUCTION THE TENDER CONTRACT DOCUMENTS WEATHERTIGHTNESS remediation 43

46 Tender documents The tender documents consist of the: legal contract agreement documentation expected from tenderers general conditions of contract special conditions of contract ( P&G ) sections of the specification. construction documents (refer to 3.11) working drawings technical specifications pricing information (sums, rates) other building consent requirements eg, scope of work, quality assurance schedule. The consultant s role The role of the consultant should be defined in a consultant/owner agreement, including the consultant s role in the owner/builder remediation contract. The latter is usually defined in the general conditions of contract mentioned above. Consultant s role The owner needs to understand roles and responsibilities created by the contract, including the fundamental requirement for the consultant to administer the contract fairly and without bias. Consultants will often need to give owners guidance on the practical effects of building (remediation) contract clauses, because some owners can be confused by parts of the standard conditions of contract and its terms Specific conditions of contract Section 3.11 considers the technical aspects of contract design and documentation. However, specifications must also cover operational and procedural issues that apply to the contractual arrangements of the remediation project. Many of these specific conditions are covered within the preliminaries and general ( P & G ) sections of the specification. These requirements must complement the general conditions of contract in order to avoid later conflicts and should cover all of the circumstances that apply to the type of contract, building work and site conditions (refer to Preliminaries and general ). Preliminaries and General Matters to be covered include: documentation, compliance issues, nominated suppliers etc site roles and responsibilities owner occupation of the building insurance covers, periods and details payment terms, dealing with variations Construction Contracts Act (CCA) QA programme (if BCA requirement) defect retentions (amounts, periods applying) special protection requirements (health and safety, security for occupants etc) weather and other protection of the works and existing building working space, storage, scaffolding, access restrictions working hours, security, access to existing facilities special conditions (phones, toilets, water, power, rubbish, noise etc). 4.3 Important specific conditions The issues outlined below are not intended to be an exhaustive list of special contract conditions but rather concentrate on those that have particular significance to remediation contracts documentation and compliance Documents and submissions The consultant should establish the documentation and form for responses required from tenderers. The contract must be clearly linked to a single set of building consent documents. Multiple sets of documents with varying status can lead to confusion. Nominated suppliers and warranties Remediation projects frequently involve nominated or preferred subcontractors and suppliers. These should be identified and written into the contract. At the same time, the consultant should establish requirements for warranties, guarantees and producer statements, together with timelines for when these are expected, and identify this in the contract (refer to BCA documents ). 44 WEATHERTIGHTNESS remediation

47 The building consent Responsibility for obtaining the building consent should be clearly defined in the contract. An agent (such as the consultant or contractor) may do this, but it is the building owner s ultimate responsibility to ensure a building consent is obtained. Depending on the terms of the consultant/ owner agreement, the consultant can handle dealings with BCAs on behalf of the owner (refer to BCA requirements ). BCA requirements Some BCAs are tying consents to a specified quality assurance programme. This can set particular requirements that will need to be incorporated into the contract. Any particular requirements, such as an inspection programme, producer statements, warranties, certificates, must be clarified and allowed for within the contract documentation and during construction to avoid later problems with code compliance certificates. Amendments during construction The consultant should generally be responsible for documenting amendments to the building consent during construction (and seeking BCA approval for these as required). If the main contractor is required to submit information for amendments, this should be defined and covered within the specification. Variations Remember that work on any variations affecting NZBC requirements cannot legally begin until the BCA has approved them and a way of recording these on the consent documentation has been agreed. This can cause delays. BCA documents Building consent documentation required by the BCA must be allowed for. The BCA should be consulted on any particular requirements (including any additional details as work progresses). At the same time, particular policies with regard to documentation such as producer statements, warranties and the like should be confirmed and covered in the specification. The consultant should also be aware of subcontractors (such as plumbing and drainage, electrical) who are expected to provide as-built drawings and/or compliance certificates for their particular sections of the works as part of separate compliance requirements (refer to BCA documents ). Further detail Section 5.1: Contract completion The code compliance certificate Required procedures on completion of the project also need to be defined. As with the building consent, it is the owner s ultimate responsibility to ensure a code compliance certificate is obtained. If it is intended that the contractor will seek the code compliance certificate on behalf of the owner, then this must be specified. If not, the relevant requirements must be defined and specified. This also applies to expectations around substantial completion of the work (including staged completion of parts if applicable). Further detail Section 5.1: Contract completion General roles and responsibilities Communications Appropriate site responsibilities must be defined, including the requirement to maintain a representative of the main contractor on site throughout the contract period. Lines of communication must also be clarified. This will ensure site workers receive instruction from only one source, and that any issues are fed back from the owner, site workers or sub-contractors to the consultant (refer to Consultant liaison ). Consultant liaison In addition to administering the contract (and interpreting the contract documents fairly), the consultant represents the owner during construction and provides overall liaison between the contractor and owner. This includes progress reporting and seeking owner decisions during construction. WEATHERTIGHTNESS remediation 45

48 Meetings and inspections Meetings should be held throughout the project. The number and frequency will be determined by the size and complexity of the project. Some meetings will involve just the consultant and contractor, to resolve technical details, or for monitoring construction quality at critical points in the repair work. The specification should require the contractor to allow for regular meetings and for taking minutes if required (in practice it is often common for the consultant to take the minutes). It is also important to allow for BCA inspections in a timely manner as they are mandatory (refer to BCA inspections ). BCA inspections Allowance for inspections required by the BCA will also be needed. This should include providing inspectors with access to all parts of the work. The BCA should be consulted on any particular requirements for inspections as these may differ according to location. At the same time, particular policies with regard to final inspections and Code compliance issues should be clarified to allow any relevant matters to be covered in the specification. Sampling and framing replacement Responsibilities and arrangements for taking samples of timber framing and other materials for laboratory testing, and for the replacement of damaged framing, need to be clearly defined. Further detail Section 4.4.3: Timber replacement, Appendix 2: Timber rot and moulds occupancy and insurances Occupation during construction Before the design is completed, and the project documentation and budgets are finalised, the owner should decide, with advice from the consultant, whether to occupy all or parts of the building during the remediation project. Drawings and specifications should therefore assume occupancy or vacancy of the site. The conditions of contract will also need to be adjusted to reflect this (to include the requirement for parts of the building to be vacated to fit with the programming of construction activities if applicable). Further detail Section 3.9.1: Project programming The continued occupation of the building can affect other site requirements, particularly work that is likely to impinge on the safety and day-to-day activities of the occupants. The owner should be made aware of the advantages and disadvantages that are involved in the building being occupied during remediation work. Insurances Whether or not the building is occupied, the owner s insurers will need to confirm the extent and status of cover under the existing house and contents policy over the construction period, and any additional or special cover that will be required. It is generally practical for the owner to extend their insurance policy to cover Contractors All Risks (often referred to as Contract Works insurance) for the period of the project, and it is important that the division of insurance between the owner and the contractor is clarified prior to tender (such as responsibility for security and health and safety on the site, theft, damage, responsibility for unfixed materials, plant and equipment). Third party covers any other special risks where needed, and should be in the joint names of the owner and the contractor (appropriate public liability insurance). The consultant should establish the minimum levels of required cover in consultation with the owner and identify that value in the special conditions. Off-site storage Storing materials for the project away from the site should be avoided where possible because of the problem of insuring against ownership disputes (in addition to the usual risks of damage, theft or fire). 46 WEATHERTIGHTNESS remediation

49 If the building is vacated, the contractor then has possession of the site and their insurance should cover the whole of the building, the construction work, as well as plant, equipment and materials stored on site. If household contents are left on site, the responsibility for insurance cover for these must be resolved and defined contract payments Progress payments The terms for progress payments should be outlined. These must comply with the requirements of the Construction Contracts Act 2004 (CCA). If payment terms are covered within the general conditions of contract, they should also be checked for compliance with the CCA. A payment schedule (prepared by the consultant in consultation with the owner) is often included as part of the tender documents. The contractor will then base progress claims on this schedule, with any changes explained and calculated. (Under the CCA, if a schedule is not included, the contractor s claim will by default be the claim to be paid.) The format of progress claims, with progress reports and certified time sheets for reimbursable work (signed off by the consultant) must be clear and fair to all parties. Details on payment processing times (including the effects of late payments) should be provided. Also specify the period for submitting the final account and release of retentions (refer to Retentions and bonds ). Retentions and bonds The amounts and liability periods that apply to any retentions must be clearly stated. Liquidated damages or similar remedies for late completion are not usually applicable to this type of work, so the owners need to be aware of the time flexibility required. In special circumstances, contractors or owner s bonds can be required. Should bonds be needed, specialist advice should be sought. Variation costs The requirements and procedures that apply to the costs of variations must be covered in the conditions of contract (refer to Variations ). A contractor is entitled to recover any variations in costs from the initial pricing as outlined in the contract documents, including all relevant overheads and profit margins. The owner, however, is also entitled to pay only fair and justifiable costs for extra work and a fair credit for work not completed. Variations Contract clauses should cover: changes in: amount of work done material types installation methods underlying conditions revealed unforseen additional work owner-requested changes record-keeping requirements. Uncertain costs It is almost inevitable that the repair work will reveal unforeseeable hidden problems that must be remedied. A system for handling this type of work is necessary. Payment processes for work done within provisional sums and prime cost items should therefore be clearly defined (including how margins will be adjusted and what rates are required for the work). Clarity The specification should clearly define what rates are expected to include, as poorly worded clauses lead to misunderstandings and disputes. Provisional work may be based on a cost plus basis (materials plus time costs) or a unit rate basis (where the type of work is known but not the amount). Prime cost items mean sums can be set aside for specific items (such as new floor coverings), the detail of which is agreed prior to the expenditure of the sum. WEATHERTIGHTNESS remediation 47

50 4.3.5 Special protection requirements Health and safety Disturbing moulds In remediation construction work there are particular hazards related to disturbing potentially toxigenic moulds during building activities. Health and safety considerations to the building site are essential. The consultant must ensure the contractor s health and safety policies are project-specific and presented with the tender. Health and safety procedures are necessary for protecting workers on site (and any occupants) during construction. Reasonable care must also be taken to prevent any unauthorised entry to the building site. Robust health and safety procedures must be established and implemented to ensure that workers are safe when they are handling potentially harmful materials. Further detail Appendix 2: Timber rot and moulds Weather protection It is important that dry areas of the building remain weathertight during construction. Good temporary weather protection covers will speed repairs and provide adequate protection. Building protection requirements must be clearly outlined in the contract to allow for the appropriate equipment (which can be costly) to be provided. If inadequately provided for, some tender bids can appear deceptively attractive when compared with others, resulting in later problems construction activity issues The conditions of contract must also clearly define any other issues that are specific to the particular remediation project such as, site working areas, storage, availability of facilities and services, working hours, access and noise restrictions, rubbish disposal and any other additional elements that could impact on the progress of the project. Project meetings Initial meeting Matters to be covered should include: introduction of relevant representatives communication and site responsibility issues scheduling of project meetings reviewing the contractor s construction programme reviewing payment schedules and processes processes for resolving construction discrepancies reviewing the list of subcontractors and suppliers processes for dealing with uncertain work BCA liaison and inspection requirements health and safety matters any other design clarifications or procedural issues any of the owner s concerns and questions. Ongoing meetings The agenda should include: a review of: construction schedule relevant quality issues costs and overall budget construction activity issues unanticipated delays design clarifications contract variations, owner s concerns unforseen extra work, decay etc health and safety matters. Care of existing property As well as the above, provisions for ensuring the existing building and its surroundings are appropriately protected against damage during construction activities should be clearly defined within the contract. 48 WEATHERTIGHTNESS remediation

51 4.4 during construction Apart from representing the owner during the construction phase, the consultant has two principal roles, contract administration and general review. Depending on the circumstances, a consultant may also provide construction management services contract administration Initial site meeting The first site meeting should take place before the project work begins. This initial meeting is important for clarifying and agreeing on various procedural issues for the project. It is particularly important to emphasis the protocols expected for communication throughout the contract. The meeting should involve the owner (or their representative), the consultant and the main contractor (refer to Project meetings ). Ongoing meetings Regular site meetings should be held during the construction process, with participation of the owner, consultant and main contractor varying according to the particular stage of the work (refer to Project meetings ). General review Matters covered should include: monitoring and approving work quality approving progress payment claims approving variation or provisional cost claims interpreting contract document requirements providing explanations, interpretations, clarifications and extra instructions updating drawings etc if required providing variation instructions (and any role in amending consents) reviewing contractor s variation claims verifying substantial completion verifying final completion and Code compliance. While most matters can be dealt with on a dayto-day basis, regular meetings allow general issues and anticipated problems to be addressed and recorded. Various sub-contractors or suppliers may be required to attend these meetings at critical junctures throughout the project. In remediation work, this can apply in particular to cladding and window suppliers/installers General review In addition to administering the contract and interpreting contract documents fairly, the consultant also processes payment claims, reports on progress, monitors costs and the quality of the work, and consults with the owner on decisions required during the construction process (refer to General review ). Quality assurance An owner may not always be aware of the consultant s role in monitoring quality assurance during construction, so it is important to clearly explain the limits and responsibilities involved in reviewing the construction. The consultant does not control or supervise the contractor. It is the contractor who, in accordance with the contract documents, is responsible for the organisation and methods used for construction. The consultant reviews the building work, which includes examining and reporting on quality. The normal expected level of quality assurance is of a general nature (rather than supervision of all details of construction). The contractor is then responsible for correcting any discrepancies noted, including occurrences of other, similar discrepancies (refer to Extended services ). Extended services Extended services may be negotiated between the consultant and the owner. In a very large remediation project, the appointment of an on-site consultant s representative may also be considered. Professional engineers and architects offer various levels of construction monitoring (refer to NZIA, IPENZ and ACENZ). WEATHERTIGHTNESS remediation 49

52 Inspections (consultant and BCA) Regular inspections by the consultant form part of the general quality assurance process and these must be coordinated between the consultant, the contractor and sub-contractors to ensure that all critical stages and parts of the construction work are covered. Inspections by the BCA are also required (refer to BCA inspections). BCA inspections The BCA will require inspections at key points in the building work. It can be advantageous if the consultant is present. If the consultant chooses to be present, BCA inspections should be integrated into the overall review process contract changes and uncertainties The nature of remediation work is such that unanticipated circumstances are expected more than in new construction projects. Some suggestions for handling uncertainties have been discussed in earlier sections (refer to Uncertainties ). Further detail Section 3.9.2: Estimates and budgets Section 4.3.4: Contract payments Uncertainties The greatest unknowns relate to the extent and resulting costs of structural repairs to walls, floors, decks and support structures (together with further sample testing, repairing finishes and so on). The contract should have included appropriate payment methods that would apply to different types of expected additional work based on: material plus labour costs ( cost plus ) unit price items lump sum fixed costs. Contract variations Changes during the construction process, such as those from unforeseen circumstances, ownerrequested changes, BCA requirements, and errors or omissions in the documents, are inevitable. Unit rates The use of unit rates is suitable when the type of work can be clearly defined, but not the quantity or extent. Unit rates may not be suitable for work that cannot be defined until the walls are opened. The replacement of structural components often includes replacement of other associated items that cannot be defined by the contractor in the tender. This can lead to large variations between tenderers and problems in the adjustments during construction. Materials plus labour costs For reimbursable work or contracts, the contractor should maintain daily work sheets that show the activity carried out, number of personnel on site, hours worked and materials used. These work sheets should be reviewed regularly and approved by the consultant, thereby providing ongoing monitoring. This process allows good budget control and minimises disputes over progress claims. Uncertain items The inclusion of appropriate contingency funds and provisional allowances in the contract can help to cover areas where additional work is expected, but where costs cannot be estimated until the full extent of the damage is revealed (usually when the cladding is removed). Costs of work on provisional items can be based on unit rates, materials plus labour costs or requested fixed-price quotations, depending on the nature of the work. Some contracts may be based entirely on cost reimbursement. Accurate record-keeping is essential in all cases (refer to Unit rates ). It is also possible to include provisional numbers of hours in the contract, based on a consultant s experience of similar projects. These hours can then be priced as part of the tender. As work is completed, actual hours are compared with contingency hours, resulting in a credit or debit adjustment. Further detail Section 4.3.4: Contract payments 50 WEATHERTIGHTNESS remediation

53 Fixed-price quotations may be used when the extent of extra work is revealed (for instance, following the removal of cladding) and is able to be defined clearly and measured. A price for the extra work is then submitted and approved in total. Timber replacement As existing framing is exposed during the repair work, decayed timber that will need to be replaced may be revealed. Control sampling should be carried out early in the construction process in order to set the testing levels to be used later as reference points. As decay is revealed, further sampling and laboratory testing will be required to ensure that the framing to be left in place is sound and unlikely to contribute towards future failure (refer to Framing replacement ). Framing replacement While the contractor is expected to recognise possible decay and raise any concerns about the framing, it is the consultant who is responsible for the identification of timber decay, including arranging for sampling and testing to establish the extent. The consultant is then responsible for instructing the builder on which areas require replacement. The in-situ treatment of retained timber must also be considered as part of this process. Further detail Appendix 2: Timber rot and moulds Existing construction The consultant s review role is generally limited to those areas of the building that are directly affected by the remedial work (as defined within the drawings and the scope of the works). However, deficiencies in the existing construction may be exposed that will need to be addressed during the remediation construction. As well as overseeing the replacement of decayed timber, the consultant is also responsible for ensuring that any sub-standard framing or structure is upgraded to meet Building Code requirements (refer to Existing framing ). Existing framing As well as decay, common deficiencies in timber framing can include: missing or sub-standard studs/dwangs missing, corroded or sub-standard fixings lack of adequate structural supports inadequate deck balustrades. Monitoring costs Buildings that are in a much poorer condition than expected place an additional financial burden on owners. It is important for consultants to keep owners up-to-date on contract expenditure against contingency sums (variations). The consultant should maintain running estimates of cost increases and regularly provide the owner with projected final cost expectations. Owners will usually have based their contractual agreements on initial costs estimates provided by a consultant at commencement of the work, and will expect to be advised in advance if these are likely to be exceeded. This provides owners with an opportunity to arrange additional finance where necessary or to investigate possible reductions in the original scope of work. Further detail Section 3.9.2: Estimates and budgets Any variations from the building consent drawings, especially significant changes, will need to be approved by the BCA, who may also require consent drawings to be amended during construction or to be submitted as a final set of marked-up drawings that record the amended consent. Designers should discuss with BCAs, requirements for variations at outset of the work. Building defects, damage and deterioration need to be documented by the consultant as the structure is opened up during construction. This record can include photographs, analyses of timber or material samples, failed original components, and any other evidence collected during the completion of the remedial work. This evidence forms an essential audit trail, which the owner may later require if legal issues are pursued. WEATHERTIGHTNESS remediation 51

54 4.5 Substantial completion It is important to remember that the project is not complete until the BCA is satisfied that the remediation work complies with the Building Code as set out in the consent documentation. The remediation work may be sufficiently finished to allow occupants to move back into the building but there may be a number of unfinished items, outstanding documentation and defects still to be remedied. Substantial or practical completion The meaning (and relevance) of these terms should be defined by the particular conditions of contract used for the remediation project. It is important that this stage be linked with the completion of all Code compliance issues identified by the BCA. The consultant should ensure that overseeing the project continues once the project has been substantially completed, because it can be easy to lose sight of the contract work at this stage. The final section of this guide discusses matters that need to be completed or finalised as part of the post-occupancy stage of the remediation project. 52 WEATHERTIGHTNESS remediation

55 5 Post-construction stage At this stage, the building work should be substantially complete. However some building work may still need completion or resolution, as well as the collection of outstanding documentation such as producer statements, warranties, certificates and so on. 5.1 contract completion Building Code compliance Time limit Be aware that, under the Building Act 2004, a 2-year time limit is set for issuing the code compliance certificate. An extension may be applied for and granted by the BCA if circumstances are considered to warrant an extension. Part of the consultant s responsibility should be to ensure that all outstanding items are completed and approved by the BCA. Owners often need to be guided through these final steps including the application for and obtaining of the code compliance certificate. Depending on the terms of engagement, the consultant may act as the owner s agent. Records and other documentation Required documentation Ensure all required documents are collected prior to final payments otherwise it may be difficult to ensure these are completed. The consultant should already be familiar with the BCA requirements for documentation such as producer statements, certificates, warranties and other records, and ensure that the relevant parties provide these. The BCA may require a marked-up set of contract drawings in order to record approved amendments to the building consent. How replacement timber framing is to be recorded should have been clarified as part of the tender process, and the BCA should be consulted on any specific local requirements. Final meeting A final meeting should be held involving the consultant, contractor and the owner to hand over all the documentation, including: code compliance certificate final as-built drawings warranties and guarantees technical instructions and data sheets lists of important trades and contacts any other important information. Minutes of this meeting should record the handover of the documentation. Release of defects retentions The period of liability applying to defects retentions will have been set by the special conditions of contract (or by default by the general conditions). The consultant should review the building work before the expiry of this period, and notify the contractor of any items requiring attention. 5.2 Post-contract matters Project information Providing the owner with guidance about building maintenance will allow them to manage the building to achieve ongoing weathertightness and pass maintenance information on to successive owners. Warranties, guarantees, compliance certificates, technical data sheets and other manufacturers information on installed materials and components should be collected by the consultant on behalf of the owner. A list of names and contact details for the contractor, subcontractors and suppliers involved in the project (with their areas of responsibility) can also be included. The collection of documents shown in Figure 17 can form a basic building envelope manual for the owners and provide a framework for developing a maintenance plan for the building. Additional information can be added to provide more detailed maintenance and monitoring guidance, if appropriate to the scale and complexity of the building. WEATHERTIGHTNESS remediation 53

56 Figure 17: A basic maintenance manual Materials and components (Manufacturer s maintenance instructions) Other certificates Warranties Certificates Producer Statements As-built drawings Materials and components (Technical installation information) Maintenance Manual Consent CCC Contractor Subcontractors and Suppliers (names and contact details) Durability under the Building Code The effective maintenance of claddings is important to ensure compliance with Building Code Clause B2 Durability (which requires certain minimum durability periods to be achieved for various parts of a building). Maintenance is the responsibility of the building owner. The Code bases the durability requirements on normal maintenance, although that term is not defined in the Act. The Department has stated (in various determinations) that normal maintenance is considered to be work generally recognised as necessary to achieve the expected durability for a given element. For claddings, this will depend on the material or system, its geographical location and the level of exposure (refer to Normal Maintenance ). Although the Building Code sets minimum requirements, building owners may elect to go beyond these minimums to consider longer-term maintenance planning as discussed below. Normal maintenance The Department has stated (for claddings) that normal maintenance tasks should include, but not be limited to: where applicable, following manufacturers recommendations washing down surfaces, particularly those subject to wind-driven salt spray re-coating protective finishes replacing sealant, seals and gaskets in joints maintenance and monitoring Owners of large and complex buildings should consider the benefits of commissioning a detailed maintenance plan. Consultants may be able provide advice on this. Maintenance planning involves describing and scheduling inspection, monitoring and maintenance tasks. The maintenance plan for a building is unique and should reflect the building s cladding systems, its geographical location and the level of exposure (refer to Maintenance planning ). 54 WEATHERTIGHTNESS remediation

57 A maintenance plan should also reflect the technical competence of those who will be involved in following the guidance provided. Specific guidance will be needed for owners or residents (in contrast to professional and experienced building managers). Specific guidance on maintenance will be particularly critical for any cladding areas that have been left in place and that may rely on sealants to remain weathertight. Maintenance planning A maintenance plan should identify and describe the: particular building component (eg, wall claddings, windows, flashings) type of inspection required (what to look out for) routine maintenance required (such as washing, repainting etc. the time frame or frequency (eg, annual, 6-monthly) work needed if problems noted (eg, for joint seals, gaskets). This should be outlined for all important visible components. Renewal plan A renewal plan should identify and describe: the particular building component (eg, the cladding material, windows, roof) the renewal recommendation (eg, recoating, replacing) the likely time until replacement (or phased replacement if applicable) any warranty expiry dates applicable code durability dates if applicable the replacement cost (in current dollars). This should be outlined for all important visible components Planning for renewal Planning for renewal identifies the timing, cost and nature of the expected repair and the replacement of elements and components that have a limited expected serviceable life. At the same time, this planning allows for renewal of some items that have deteriorated prematurely. A renewal plan is likely to be based on a theoretical knowledge of expected durability and information from the applicable manufacturers. Maintenance plans help with renewal planning, as inspections will trigger the renewal of some materials (and will keep the renewal plan up to date). The benefit of renewal plans for larger multi-unit developments is that they allow a body corporate to prepare for gradual financing (refer to Renewal plan ). WEATHERTIGHTNESS remediation 55

58 Appendix 1: Areas of risk The following table lists the high-risk locations that were shown in Figure 3: Common areas of weathertightness risk, and includes examples of common defects (along with an indication of the incidence of defects in such locations based on a recent study) (note 1 on page 58). Table 5: Common weathertightness defects Detail Description Examples of possible defects % (1) 1 Cladding general Base clearances Inadequate cladding clearance above ground Bottom of cladding buried Floor to ground separations 64% 2 Body of cladding Cracking 55% Vertical control joints No or poor control joints 50% 3 Horizontal control joints No control joint, unflashed joint Poor overlaps, flashing traps moisture 4 Horizontal joints corners Gaps, poor seals, no soakers 5 Cladding base No anti-capillary gap/poor overlap No plaster drip edge 45% 6 Inter-cladding junctions No back-flashing, scribers etc 27% 7 Sheet joints Joints pouting, nails popping Joints lining up with window jambs 8 Material quality Sub-standard solid plaster Sub-standard weatherboard profiles 20% 20% Paint coating/sealer defects 14% 9 Cladding top Poor barge flashings Inadequate overlap/no drip edge Unsealed under fascias 10 Decorative bands Unsealed fibre cement under bands Flat top/cracks 19% 15% 11 Corners No back-flashing, scribers etc 12% 56 WEATHERTIGHTNESS remediation

59 Table 5: Common weathertightness defects (continued) Detail Description Examples of possible defects % (1) 12 Windows and doors Jambs Unsealed under jamb flanges No jamb flashings where required 13 Sills No drainage gap at sill flashing No or inadequate flashing where applicable 14 Sill/jamb junctions Poor seals/no soakers where needed No sill flashing turnups 15 Head/jamb junctions Inadequate/unsealed head projection No returns to head flashings 16 Heads No drainage above flashing slope Inadequate head flashing 29% 9% 30% 27% 23% 19% 18% 17 Curved/raked heads Inadequate head/jamb junctions 30% 18 Garage heads No head flashing. No drip edge 10% 19 Garage jambs Unsealed/unflashed jamb liners 8% 20 Garage jambs bottom Clearance from paving 21 Parapets Parapet/roof junctions Inadequate flashings 22% 22 Parapet tops No capping. Flat top. 50% 23 Parapet tops -corners Poor capping joints 38% 24 Roof drainage Rainwater outlets Unsealed scuppers No overflow provisions 11% 25 Downpipe spreaders No or poor spreaders 4% 26 Roof edge/gutter Inadequate overhang, gaps Building paper not overlapping gutters 4% 27 Roof flashings Wall/roof apron flashings Inadequate upstands/overlaps 9% 28 Apron flashing bottom No kickout, poor sealants, gaps, bare fibre cement/framing etc Gutters/fascias buried 38% 27% 34% 29 Roof/wall clearance Inadequate clearance to apron 15% 30 Other roof flashings, skylights Inadequate overlaps, poor sealants 12% 31 Inter-roof claddings, skylights Inadequate overlaps, poor sealants 35% 32 Inter-roof/wall junctions Inadequate flashings 22% WEATHERTIGHTNESS remediation 57

60 Table 5: Common weathertightness defects (continued) Detail Description Examples of possible defects % (1) 33 Solid floor decks Deck/wall junctions Poor cladding clearance above deck Inadequate overlaps, capillary gaps 50% 22% 34 Deck perimeter/wall junctions Inadequate flashings 26% 35 Open balustrades Deck perimeter Poor membrane overlaps Balustrade penetrations 15% 9% 36 Balustrade/wall junction Unsealed fixings 5% 37 Clad balustrades Balustrade/wall junction No saddle flashings 52% 38 Balustrade top No slope to tops No capping Poor capping/capping joints 51% 47% 13% 39 Handrail fixings Handrail penetrations through tops 46% 40 Drainage/overflows Inadequate overflow/drainage Poor slope 41 Balustrade/deck junction Poor cladding clearance above deck Inadequate overlaps, capillary gaps 42 Timber slat decks Deck/wall junctions No drainage gaps Decking buried in coating 34% 10% 14% 47% 17% 43 Penetrations Pipe penetrations Poor seals 50% 44 Pergolas etc No flashings, poor seals etc 30% 45 Meterboxes/grilles etc No head flashings Poor sealants/gaps/cracks etc 23% Note: (1) Incidence of defects from analysis of information from a sample of about 340 houses assessed for Departmental Determinations up to December Not all defects are included in the table only the most commonly found defects are noted. 58 WEATHERTIGHTNESS remediation

61 Appendix 2: Timber rot and moulds Issues related to timber decay and mould identification are probably the least understood and most complex of the entire remediation process. There is relatively little information available for consultants or specialists on where to take timber framing samples, how many samples to take, the size of samples, and the ongoing need for sampling throughout the remediation repair process. This appendix expands on areas related to timber decay. The most critical aspect of timber decay is to determine the extent of the decay. Timber that is clearly decayed is easy to identify. The difficult part is to detect decay where the timber can appear quite normal even to a specialist. It is only when a sample is examined under the microscope by a trained and experienced specialist in fungal and mould behaviour, that the type and extent of decay can be determined. It is therefore essential to work closely with an experienced laboratory specialist who can give advice based on micro-scopic analysis. It is also important that samples continue to be sent for specialist analysis throughout the repair stage as more of the building is opened up. The process of assessing decay may be seen as four phases. 1. Before inspection 2. During inspection 3. Laboratory analysis 4. Using the results Types of rot While identification should be made in the laboratory, the following is a general guide. Brown rots usually cause wood to lighten in colour prior to becoming dark brown, and to crack along and across the grain (although only once dry). When dry, very decayed timber will crumble to dust. White rots cause the timber to become lighter in colour and fibrous in texture without cross-checking. Dry rot is the common term for one brown rot Serpula lacrymans, and is relatively rare in New Zealand. However, it is also difficult to distinguish from other brown rots so field observations must be backed up with laboratory testing. The main concern with dry rot is that decay is very rapid once suitable conditions prevail and it can move moisture considerable distances to dry wood and cause decay of timber that would have otherwise remained dry and resistant to other types of decay. Wet rot refers collectively to all other brown rots and white rots. Soft rot often shows little outward sign of decay in the affected timber (ie, classical softening is absent). Sometimes the timber may become a dirty grey-tobrown colour. When a sample (at least the size of a matchstick) is broken off, the fracture surface can sometimes look like a broken carrot (although juvenile wood without decay behaves similarly). A 2.1 before inspection Collect information and identify particular risks as discussed in Section 1: General information collection stage to help determine where cladding cut-outs should be made and timber or mould samples taken. Further detail Figure 3: Common areas of weathertightness risk Section 1.1: The property, Section 1.2: Construction history WEATHERTIGHTNESS remediation 59

62 A 2.2 during inspection The on-site inspection is part of the extensive diagnosis process described in Section 2. Before any moisture testing is undertaken, any early evidence of possible decay should be noted in order to inform the testing process (refer to Early indicators of decay ). Moisture readings Moisture readings should first be taken in the non-destructive or capacitance mode, followed by drilling holes through the cladding into the framing and taking readings in the resistance mode Critical factors in both modes are to identify relative rather than absolute values. A useful approach is to identify a location that is known to not be affected by moisture penetration. This can be used as a control with other moisture readings compared with it. Further information on the use of moisture meters (including limitations) is provided in Section 2. Further detail Section 2.2.2: Step 2: Non-invasive testing Early indicators of decay Internal Occupants knowledge of leaks, locations and length of time of moisture problems Occupants comments about health problems that could be related to toxic moulds Visible signs of dampness, mould and decay (eg, corroding carpet fixings, swelling skirtings, cracked linings etc) Odours such as a distinctive mushroom smell associated with decay fungi External Cracking in cladding and/or staining and discoloration are often reliable signs of moisture ingress and subsequent timber decay Moisture travel Moisture problems can occur remotely from leak sources. It is important to allow for the possibility that evidence of moisture can show in unexpected positions and/or may be concealed. An example of this is where (maybe due to daytime temperature fluctuations) external moisture evaporates within cavities; the vapour redistributes and then condenses as moisture elsewhere. Taking on-site samples The decision on how many and where samples should be taken for laboratory analysis is not straight forward. It requires careful consideration and an understanding of possible moisture behaviour within building walls (refer to Moisture travel ). The number and location of samples taken are influenced by the following factors. Whether framing is known to be treated or not The length of time the timber has been subject to excessive moisture The extent of decay as assessed from on-site observations Information from drilling and other on-site testing (refer to On-site techniques ) Whether the likely repairs are tending toward complete recladding or targeted repairs Whether initial assumptions on decay are confirmed by laboratory analysis The costs of taking extra samples at a repeat visit if initial assumptions prove incorrect Whether laboratory analysis is required as part of a dispute resolution process The consultant s or specialist s experience (refer to Using experience) 60 WEATHERTIGHTNESS remediation

63 On-site techniques Useful site techniques (which should be confirmed by laboratory testing) include the following. Observing timber hardness when drilled and the nature of the drillings and comparing this with a control point in known sound timber. Probing timber with a sharp tool such as a chisel. If the timber breaks off into short splinters ( brashness test ) when levered by the probe it is usually an indication of decay and loss of strength. Softness of the timber is also a useful indicator of decay (although juvenile heartwood may be soft irrespective of the presence of decay). Striking the timber with a hammer or something similar. A hollow sound from a larger timber member, or a change in note along a length of timber might indicate decay. It is important to confirm (or otherwise) the results of on-site testing with laboratory analyses of representative samples. Samples of untreated timber The use of untreated kiln-dried timber for external wall framing was very common from 1996 to If on-site testing indicates that timber is untreated and decay is widespread, then only a few samples may be required because the need for recladding and major timber replacement will be obvious. If in doubt check The golden rule is, if in doubt check, either by taking another sample or seeking another opinion from another remediation authority. Remember that remediation is a team effort, with the underlying feature being the provision of adequate information to all those involved at every step, so that risk analysis is applied effectively. Lack of information can quickly become a major and perhaps insurmountable problem. The experience from overseas on these issues has taught us that failure to conduct adequate investigation greatly compounds problems. In such cases, the main reasons for sampling will be to ensure the owner has sufficient evidence that a reclad is required. Reasonable evidence of untreated timber includes observing markings on the timber and/or spot tests. Laboratory analysis can confirm that the timber is untreated and also the extent of decay. Using experience A very experienced remediation specialist: will be confident as to what is sound timber and what is decayed from observations and testing may take 2 3 samples per elevation for analysis at the fringes of decay will, if initial assumptions are not confirmed, take further samples for analysis. A less experienced consultant may take more samples because of uncertainty about the extent of decay. However, consultants should remember that some decay is impossible to detect without the backup of laboratory analysis. Samples of treated timber Cost-effectiveness Because timber can look sound but be decayed, it may be more cost-effective to take further samples initially (to be sure of the extent of decay) than to place reliance on experience that may prove to be wrong (and therefore lead to additional site visits and sample collecting having to be undertaken). If the timber is treated, more samples may need to be taken than for untreated timber. Untreated timber exposed to excessive moisture is likely to have severe decay after 3 to 12 months, but treated timber may be satisfactory for 2 to 5 years. If treated timber has widespread decay because of leaks over a long time, recladding and major timber replacement will be necessary (as discussed above, relatively few samples will be required). However, if the leaking is relatively isolated (with limited decay), further samples may be required in order to reliably establish the extent of decay. Further samples will be required when targeted repairs are an option, because the aim is to determine the limits of the decay (taking into account the rule-of-thumb that all timber within 1 metre of the outer limit of the decay must be removed). Size and nature of samples Practices vary regarding the size and nature of timber samples that are taken. Although laboratory analysis of very small samples is possible, it is best to submit as large a sample as possible in order to maximise the potential forensic WEATHERTIGHTNESS remediation 61

64 information (which includes measuring the degree of decay, how long it has been occurring for and the extent of leaching of preservative across the section of timber and so on). The largest framing sample would normally be about a 100 mm in length. Samples should be included which are taken from timber that is considered to be at the least decayed end of the spectrum, to set benchmarks. The nature and size of samples also depends on the forensic information required. If the aim is to determine the length of time that the building has been leaking at a particular location, it may be important to send a sample from a clearly wet area and one from a reliably dry area. The length of time that the building has been leaking can then be estimated by the degree of leaching of the preservative compared with the piece of timber that has not been subject to moisture. The type, location and extent of decay will also enable the duration of the leak to be estimated. Sellotape sampling for moulds The simplest way to take a sample is to use a piece of sticky tape, which is pressed down on the mould or fungi, transferred to a grease-proof paper envelope and then placed in a sealed plastic bag for sending to the laboratory. While Sellotape samples are satisfactory, more useful forensic information can be obtained by sending a sample of the actual material (eg, building paper or plaster board etc) with the mould attached to the laboratory for analysis. Records Photograph all decay samples, both close up and from further back to show relative locations of samples on the building, as this helps with interpreting test results. When sending samples to the laboratory, it is helpful to provide photographs showing where each sample has come from. Photographs should also be provided which give an overall perspective of the type of building under investigation (showing cladding etc), in order to assist with the forensic analysis of the samples. Health and safety issues When extracting samples, it is important that precautions be taken to guard against any potential hazards to those involved with the remediation work, including occupants of the building. Occupants health Diagnosis of the potential for adverse health effects from mould and other micro-organisms (eg, actinomycetes and bacteria) and their by-products is often not straightforward. The amount of affected material and its location, and the type of micro-organisms can all have an effect. Experience is important, and advice from a specialist in fungus and mould should be sought to keep people informed of potential risks. When taking samples: be careful to use suitable protective equipment including appropriate breathing masks and gloves remove cladding from the outside of the building rather than from the inside wherever possible (to allow any potentially dangerous fungi such as stachybotrys to be released into the atmosphere rather than into a living space inside the house) disturb the mould and fungi as little as possible (for instance, stachybotrys atra is far more dangerous when it has dried out and the spores readily become airborne. When wet, the spores tend to stick together and are less likely to become airborne and breathed in by the building user) carefully seal off any voids that may have been opened up as part of the investigation process. A 2.3 laboratory analysis Identifying timber treatment Laboratory testing is important to determine clearly the type and level of timber treatment, because doing this on site can be difficult. Site testing for boron or copper-based preservatives can be successful, but accepted guidelines must be followed and the limitations and reliability of such tests need to be appreciated. 62 WEATHERTIGHTNESS remediation

65 Moulds and fungi The analysis of moulds and fungi found on site can only be undertaken by experienced specialists. The results of laboratory analysis can be used to provide information on issues such as the type of mould, its toxicity, how long it has been in place, and forensic details of the type of moisture elevation scenario. Some moulds (such as stachybotrys atra and Chaetomium globossum) also cause decay in particular situations, and specialist knowledge is necessary to establish their significance in any given scenario. Dormant fungi Decay fungi can remain dormant in dry timber for many months and up to several years in some situations. This should be no surprise considering how long bakers yeast (also a fungus) can remain dormant in its dry form. Laboratory testing can determine if decay was recently active or not, or if it is still viable in the case of very old infected or decayed wood. Moulds and fungi can grow on any surface. While many do not pose health risks, stachybotrys atra and some other types of mould are toxigenic and have been implicated in building sickness syndrome. Stachybotrys atra is most commonly found on gypsum paper board, fibre-cement board, building paper and other cellulose containing materials. A 2.4 using analysis results The results of the laboratory tests (combined with the systematic off-site and on-site investigations) can provide valuable information (refer to Specialist laboratory advice ). The information will allow conclusions on the: extent of timber damage and therefore extent of replacement timber to be estimated time restrictions to be established for remediation measures to be put in place extent and type of treatment required for replacement timber to be decided. In this way, on-site information and laboratory testing allow an outline scope of work to be established, together with rough estimates of likely costs. Further sampling and analysis will be required through the remedial construction stage to confirm the integrity of timber to be retained. In-situ treatment In-situ treatment Some concentrated preservatives (applied by brush or airless spray) are commonly used in New Zealand. Boron-based in-situ preservative requires predampening of the timber. LOSP (Light Organic Solvent Preservative)-type preservatives can be suitable in some situations, provided the wood is essentially dry. Specialist laboratory advice Advice can be available on the following. Current condition Type and extent of decay Presence of wood preservative Retention levels and type of preservative History How long the decay has been present How long the leak/fault has been present Future How quickly decay will continue to develop If no decay, future risks of wood failure Repair How much framing needs to be replaced Type of replacement framing to be used Speed of drying measures needed Appropriateness of insitu preservative application and the type recommended In some instances, it may be appropriate to undertake targeted repairs, that is, leaving the timber in-situ and applying suitable preservatives. In such cases, it is important to follow the advice of a laboratory specialist who is experienced in the use and effectiveness of in-situ timber treatment. WEATHERTIGHTNESS remediation 63

66 Appendix 3: Checklist for information collection File No. BCA Substantially completed Survey date Address Certifier GENERAL: Building type Risk (enter no. of elevations) Wind Exposure Detached house Low Low Complex Number of units Moderate Medium One unit or all of complex High High Alterations/additions Very high Very high Specific design zone Recladding of existing building Floor/foundations Site slope Other site conditions Concrete/concrete block Flat or nearly flat (note) Number of storeys Retaining walls? Moderate slope Reason for survey Timber-framed Steep slope WHRS claim DBH Determination Concrete perimeter walls? Other specify ROOFS main others main others Complexity Pitch Materials Not applicable Less than 5 o Profiled metal Simple monopitch/curve 5 o to 10 o Membrane Simple gable/hip 11 o to 20 o Pressed metal tile Moderately complex 21 o to 30 o Masonry tile Complex 31 o to 40 o Asphalt/fibreglass shingles Very complex over 40 o Timber shingles Curved roof: Other specify Convex Concave Design Features Parapets Hips Dormers Monolithic clad Gables Skylights Monolithic top Monopitches Oblique eaves Parapet capping: Stepped Exposed rafters Metal Other other Membrane Overhangs (including gutters) (only if significant) Other Eaves main mm Eaves other mm Slope to parapet top: Verge main mm Verge other mm Flat/almost flat Walls with gutter only or less Less than 10 o Few Some Most 10 o or more 64 WEATHERTIGHTNESS remediation

67 WALLS Complexity Timber treatment Wall cladding materials main others Very simple box-like Unknown cavity? Simple shape more corners Untreated Stucco (solid backing?) Moderately complex Insecticide only EIFS (plain or grooved back?) Complex shape Older boron/ H1plus/ H1.2 Flush-finished fibre cement Very complex shape Douglas fir Fibre-cement sheet other Design Features Native Timber w/bd horizontal Pergolas/porticos etc. Other specify Timber w/bd vertical Monolithic columns Windows Fibre cement w/bd Monolithic flying beams Aluminium Brick or block veneer Monolithic clad chimney Curved heads Concrete block/concrete Decorative bands Raked heads Prof metal horizontal Other features specify Timber Profiled metal vertical Overall impressions of workmanship (Walls/roof) Other specify WEATHERTIGHTNESS remediation 65

68 Appendix 4: Additional resources Listed below are resources that provide additional detail on points raised in this guide. Department of Building and Housing Publications are available from the Department (free download from or freephone Acceptable Solution E2/AS1 External moisture A guide to using the risk matrix: June 2005 External moisture An introduction to weathertightness design principles: August 2006 Constructing cavities for wall claddings Characteristics and defects a study of weathertightness determinations: April 2007 Guide to applying for a building consent simple residential buildings: 2007 Timber treatment summary information from NZS 3602: 2003: June 2007 Canada Mortgage and Housing Corporation Building Envelope Rehabilitation Consultant s guide: 2001 Building Envelope Rehabilitation Owner-property manager guide: 2001 Occupational Health and Safety Risks to health from mould and other fungi Workplace Health Bulletin No.17: 2002 New Zealand Metal Roofing Manufacturers Inc. New Zealand Metal Roof and Wall Cladding Code of Practice: 2003 Building Research Establishment Recognising Wood Rot And Insect Damage in Buildings: Third edition 2003 Robin Wakeling Wood Decay in Leaky Buildings: proceedings of the NZIBS Annual Conference, 2005 New Zealand Standards NZS 3602: 2003 Timber and Wood-based Products for Use in Buildings NZS 3640: 2003 Chemical Preservation of Round and Sawn Timber BRANZ books (latest versions) Stucco Good Practice Guide Timber Cladding Good Practice Guide Profiled Metal Wall Cladding Good Practice Guide Weathertight Solutions, Volume One Weatherboards Weathertight Solutions, Volume Two Stucco BRANZ Bulletins: 304: Flashing Design 353: Ground Clearances 428: Weathertightness Do s and Don ts 434: Results of Weathertightness Failure 435: Weathertightness Evaluation 448: Domestic Flashing Installation 449: Keeping Water Out Timber-framed walls 66 WEATHERTIGHTNESS remediation

69 Glossary The following provides a brief description of the meanings intended by terms used in this guide. Acceptable Solutions Acceptable Solution E2/AS1 Active defects and Inactive defects Alternative solution Building Consent Authority (BCA) Building envelope Compliance Documents Consultant Control Cut-out Decay Defect Department Destructive Examples of materials, components and construction methods which, if used, will comply with the Building Code. They are one way, but not the only way, of complying with the Code. The Acceptable Solution for Building Code Clause E2 External Moisture. Active defects are weathertightness defects that have caused, or contributed towards, moisture penetration in contrast with inactive weathertightness defects that may allow future moisture penetration. A way of complying with the objectives and functional requirements of the Building Code that does not use the prescribed methods shown within the Compliance Documents. When proposing alternative solutions, designers must demonstrate compliance to the BCA. A BCA can be an organisation, such as a territorial authority or a private body, that is accredited to carry out certain building control functions as defined in the Building Act The outer structure of a building (including the floor if over a subfloor space), which is covered with wall and roof claddings. Documents (formerly known as Approved Documents) that set out prescribed methods of complying with specific clauses of the Building Code. The Compliance Documents contain Acceptable Solutions and Verification Methods and reference New Zealand and international standards. Though optional, Compliance Documents are commonly followed in domestic building projects because they provide straightforward paths for building. The person undertaking the remediation design and oversight of subsequent repair work. A measurement from an area (where the underlying condition is known), which is set up as a reference point against which other measurements may be compared. The removal of a small section of cladding to allow inspection of the underlying construction (including moisture and decay testing of samples of framing timber if appropriate). Various fungal diseases (caused by a number of fungi) that become established within building timbers when moisture levels are elevated above certain levels. A particular detail or location that is either causing or contributing towards moisture penetration at present, or may do so in the future. The Department of Building and Housing. Testing or sampling that involves removal of sections of cladding to examine underlying construction or to extract samples for laboratory analysis. WEATHERTIGHTNESS remediation 67

70 Detailed diagnosis Determination (and weathertightness Determination) Direct-fixed cladding Drained cavity General evaluation Invasive testing A detailed survey and investigation of a building, resulting in the assessment of likely damage and necessary repairs. A binding decision made by the Department, which provides a way of solving disputes or questions about the rules that apply to buildings. Within this guide, the term is used to describe determining matters about weathertightness and durability, and usually includes general evaluations of the buildings concerned. A cladding that is fixed directly through the building wrap to the exterior wall framing (without a drained cavity). Cavity behind a wall cladding as defined in E2/AS1 (refer to Acceptable Solution E2/AS1). A limited scope survey, where a building is assessed at a less detailed level than would apply to a detailed diagnosis (such as for a pre-purchase report or for a Departmental determination on Code compliance). Testing that involves drilling into the wall to measure the moisture content within the framing (in contrast to non-invasive testing that uses surface measurement). Iterative process The process of revisiting, adding to and reassessing earlier work based on developing knowledge. Monolithic claddings Moulds and fungi NZBC Outline scope of work Remediation Remediation strategy Risk matrix Samples or sampling Sketch design Stachybotrys atra Working drawings Wall cladding systems that are flush-finished and rely on protective coatings for weatherproofing (for example, stucco, EIFS and flush-finished fibre cement sheet). Moulds are a type of fungi, which are simple microscopic organisms that release spores able to be inhaled. New Zealand Building Code. The early recommendations for repair arising out of the diagnosis stage of remediation. The work required in order to achieve an adequately weathertight and durable building. The course of action chosen to undertake remediation work. A table from E2/AS1 used to determine levels of weathertightness risk applying to a building design. Materials removed from a building (such as timber, building wrap, linings, carpet) that will be sent away for laboratory testing. Early design stage during which options are explored and changes may be easily made. A toxigenic mould that has been implicated in health risks for some people who come in contact with it. Detailed design stage based on the chosen remediation strategy. 68 WEATHERTIGHTNESS remediation

71 This document is printed on Works Laser, a 100% recycled stock manufactured using a totally chlorine-free process.

72 Published in November 2007 by Department of Building and Housing PO Box Wellington, New Zealand This document is also available on the Department s website: ISBN: (document) ISBN: (website)