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