INSULATED PITCHED ROOFING

Transcription

1 DOW CONSTRUCTION PRODUCTS (a division of the Dow Chemical Company Ltd) INSULATED PITCHED ROOFING Welcome to this RIBA approved CPD self tutorial. First some information about the Dow Chemical Company itself: US origin, 100 years old. 2nd largest chemical company in the world Produces: chemicals, plastics, agrochemicals. Annual sales: 18 billion. Employs: 45,000 globally (Europe 8,000) Dow in the UK STYROFOAM* production since 1969 : polystyrene produced at Barry, Wales; extruded foam insulation produced in Kings Lynn. Dow Construction Products offers the STYROFOAM range of blue extruded polystyrene foam insulation: Floors - Floormate* 200,350,500 and 700 Cavity Walls Walls internally Structures below ground Pitched Roofs Inverted Flat Roofs Conventional Flat Roofs - Wallmate* CW - Styrofoam* IB - Perimate* DI - Roofmate* PR, RL - Roofmate* SL, LG - Deckmate* CM, FF * Trademarks of the Dow Chemical Company

2 Dow Construction Products Insulated Pitched Roofing This self-tutorial seminar covers all aspects of the so called Warm Roof Concept at rafter level pitched roof insulation. You will discover The insulation options The advantages of the warm versus the cold roof How a warm roof is constructed The general design considerations, relevant codes of practice and applicable standards to adhere to The role and selection of the various components with particular emphasis on the insulation, the underlay, fasteners and methods of securement The relevance and importance of the building physics issues, thermal insulation, condensation and ventilation The ins and outs of detail design: eaves, ridge, valley, hip and roof penetrations How the warm roof concept has been put to the test in the field

3 INSULATED PITCHED ROOFING INTRODUCTION: It is estimated that today around 10% of new pitched roofs are insulated at rafter level and that this figure is increasing. Various insulation solutions are available which are dependent on the type of insulation used and its location ( ie above, between or below the rafters or a combination of these ), and the type of underlay used. Although the insulation of pitched roofs cannot be considered a new application it is now the subject of much debate both in the technical press and within the industry itself - indeed the BRE, NFRC and BSI are all actively involved. The aim of this seminar is to review the application from an insulant manufacturer s point of view.

4 CONTENT Insulation options Advantages of an insulated roof structure The Warm roof concept Design considerations Roof build-up: the components Building Regulations: requirements Case study Detailing Conclusions

5 Roof structure: uninsulated attic/loft space insulation at ceiling level insulation at ceiling / joist level - mineral / glass fibre normally used attic / loft space ventilated (vents provided at eaves and at ridge) Note: Could adequate ventilation be provided by a water vapour permeable (breather) underlay and thus do away with providing vents at eaves and ridge level?

6 Roof structure: insulated insulation at rafter level room in the roof Insulation can be a) above, b) between c) below the rafters or a combination of these Warm roof insulation above rafters sometimes referred to as sarking insulation (see BRE Thermal insulation: avoiding risks BR262 Hybrid roof : insulation between and/or under rafters. Note: Focus of this seminar will be on the warm pitched roof as this is the optimum ( and perhaps the most challenging ) of the insulation options.

7 ADVANTAGES : INSULATED VS UNINSULATED ROOF STRUCTURE Increased living /working space for same footprint Additional space at lower cost Added value Allows room to grow Cost of providing additional space in the attic can be less than 50% of the standard floor cost. plus with a warm roof: - reduced risk of condensation on structural membranes. - thermal movement of roof structure reduced. - roof structure kept dry - no need for timber preservative treatment.

8 THE WARM PITCHED ROOF - roof build up Counterbatten Tiling batten Tiles Vapour permeable underlay Insulation Rafter Insulation shown above and between rafters Vapour permeable underlay (breather type) can be laid either in direct contact with the insulation ( as shown ) or over the counterbattens Suitable for new build or where the roof covering is to be replaced ( note increase in roof height! ) and where it would be difficult to provide eaves ventilation Note: Need for a vapour control layer (VCL)? YES for areas exposed to high humidity levels e.g swimming pools, kitchens, changing rooms. Use plasterboard (13 mm) to cover exposed XPS insulation.

9 THE WARM PITCHED ROOF CONCEPT rigid insulation over (and between) rafters plus a water vapour permeable (breather) underlay Note: Where proprietary products are to be specified, manufacturers recommendations should be followed. Designers should satisfy themselves that the performance of these products and the given recommendations have been proven by relevant experience in use or by test data based on the conditions and methods of application in equivalent and appropriate internal and external climatic conditions.

10 THE WARM PITCHED ROOF First thatched roofing! Developed from Scottish sarking - early 80 s Agrément certification - mid 80 s Thousands roofs, millions sq metres installed Includes all insulation types Minimal condensation problems No securement problems Note: Thatched roof - really is a breathing warm roof Sarking - originated in Germany / Scandinavia refers to a sheet or underskirt of boarding. - traditionally in Scotland 25mm thick close timber boarding at underslating level. - helps reduce effect of wind uplift on slates.

11 Design considerations! BS 5268 : Part 7 : 1990 Roof construction - rafters & purlins (Approved Document A : 1994 )! BS 5534 : Part 1 : 1997 Slating & tiling! BS 6399 : Part 1 : 1984 Dead loading! BS 6399 : Part 2 : 1995 Wind loading! BS 6399 : Part 3 : 1988 Imposed & snow loading

12 ROOF BUILD-UP - THE COMPONENTS Rafters Vapour Control Layer Insulation Underlay Battens Fasteners

13 RAFTERS Consider: Roof slope Cut vs trussed Dimensions (and tolerances) Spacing Bracing Note: Must assume that insulation does not contribute to the racking strength of roof structure.

14 VAPOUR CONTROL LAYER (VCL) Usually a membrane (eg 500 gauge polyethylene sheet) Substantially reduces transfer of water vapour Installed on warm side of insulation A VCL reduces water vapour transfer through any building component in which it is incorporated. (BRE document BR 262: Thermal insulation - avoiding risks specifies a minimum water vapour resistance of 200 MNs/g. BS 5250 refers to the use of 500 gauge polyethylene with a range of 200 to 350 MNs/g, typically 250 MNs/g.) The VCL should be installed on the warm side of the insulation. ( Note that a VCL at ceiling level will require increased ventilation below it during the wet trade phases of construction.) Performance of a VCL also is dependant on workmanship and build ability - see Clause 9.2 of BS It is essential that it is adequately lapped and sealed so as to maintain its integrity. Particular care should be given to detail design and installation around penetrations through the VCL (e.g services, compartment walls) and to the sealing of punctures caused by fasteners.

15 INSULATION Location - above / between / below (or any combination) Selection - thermal performance - water vapour permeability - water resistance (absorption) - user friendliness Thickness Installation - thermal integrity - convection tight Location: (a) over the rafters (b) between the rafters (c) under the rafters or any combination of these Note : Option (a) is sometimes referred to as a warm roof construction or as sarking insulation. All options can be used for new roof constructions or where the roof is to be replaced from rafter level up. Only options (b) and (c) can be used in situations where the roof covering cannot be removed or replaced. Selection: Rigid, semi-rigid and flexible insulants can be used. Each has its own specific physical characteristics as regards performance and installation requirements - the manufacturers recommendations should be followed. cont ->

16 Thickness: The thickness of the insulation will be determined by the required thermal performance as well as by the roof construction (see Approved Document L). It is important to ensure the continuity of the thermal insulation. If this is broken eg by the rafters and /or penetrations through the roof, the resulting thermal bridges can increase the risk of localised condensation and pattern staining of ceilings at rafter line. Note: Building Regulations require the effect of thermal bridging to be taken into account when calculating the thermal performance (U-value) of the roof. Refer to BS 5250 Section 9.6 and BRE Document 262: Thermal insulation - avoiding risks. Installation: Thermal integrity is essential. The roof void should be completely insulated. For example gable end walls will need to be insulated to their full height. The designer should take care to ensure that there are no gaps or breaks in the insulation envelope. The insulation should be installed to fit tightly at ridges, at eaves and around penetrations. Seal if necessary with flexible (polyethylene) or PU foam. Insulation boards should fit tightly together with no gaps around them. Rigid board joints should be correctly positioned so as to shed any likely incoming external water. Some types of board will require their joints to be sealed with tape - refer to the manufacturers instructions. Special care needs to be taken with rebated boards designed for over and between rafter installation e.g Roofmate PR to ensure that the rafter spacing is accurately set out so as to avoid gaps or unnecessary cutting of boards. Convection tight/airtight: A roof system in which the free movement of air through any section of the construction is prevented by use of airtight joints and seals is said to be convection tight or airtight.

17 INSULATION - typical physical properties XPS EPS PUR MF Thermal conductivity W/mK Water vapour resistance (relative to MF) Water vapour resistivity MNs/gm Water absorption % vol ? Compressive strength kpa max 175 max 120 max Density kg/m XPS EPS PUR MF - extruded foamed polystyrene - expanded foamed polystyrene (bead board) - polyurethane/polyisocyanurate - mineral fibre Thermal conductivity XPS, EPS measured at 90 days (after equilibrium reached) - long term value. PUR measured immediately after production ie before equilibrium reached - short term value. Water vapour resistance Determined relative to MF(air) for equivalent U-value thicknesses (XPS=50mm) Water absorption Be sure to take into account likely effect on thermal conductivity!

18 ROOFMATE* RL, PR - physical characteristics PR RL Density kg/m Thermal conductivity W/mK Compressive strength kn/m Water absorption % vol Water vapour resistivity MNs/gm Board size mm 2500 x x 600 Thickness mm 80, 90, , 50 Edge profile - rebated tongue & groove Roofmate RL Tongue and groove on all sides. Board should be laid so the tongues in horizontal joints face up the slope. Roofmate PR Available with edge flanged to suit 38 and 50mm rafters - type 38 and 50 respectively. Boards should be laid so that horizontal lap joints (i.e top and bottom of boards) point down the slope so that boards higher up the roof overlap those further down (boards are marked so as to facilitate this e.g with an arrow pointing up the slope of the roof).

19 UNDERLAYS- REQUIREMENTS - TRADITIONAL Keep water (snow, dust) out Air tight Adequate strength - WATER VAPOUR PERMEABLE (Breather) As Traditional plus water vapour permeability Keep water etc. out - secondary defense against wind driven rain, snow and dust. Air tight - to reduce wind load on primary roof covering. Adequate strength - tensile, tear strength (for nails), extensibility (reduce movement under wind pressure). Working temp. range - 20 to + 80 deg C. Water vapour permeability - Traditional underlay e.g BS747 Type IF felt These are defined (BS5250) as having a water vapour resistance in excess of 50MNs/g - Water vapour permeable (breather) underlay BS 4016 : 1995 Flexible building membranes (breather type) - max. water vapour resistance 0.6MNs/g BRE Thermal Insulation : Avoiding risks - specifies MNs/g.

20 UNDERLAYS WATER VAPOUR RESISTANCE Traditional Breather MNs/g BS 747 Type IF felt Monarfil* Permo* 0.20 Tyvek* HD - Soft 0.24 Tyvek* Pro 0.16 Roofshield* 0.08 Monarperm* Insulation XPS - 90mm 85 PUR - 80mm 46 MF mm 0.6 * Tradenames Monarfil reinforced polyethylene (0.25mm) Permo Tyvek Soft Tyvek Pro Roofshield - laminated spunbond polypropylene - spunbond polyethylene (0.19mm) - spunbond polyethylene / polypropylene laminate (0.42mm) - spunbond polypropylene laminate (0.60mm) Monarperm spunbond polypropylene (0.45mm)

21 BREATHER UNDERLAYS Performance criteria should reflect real life roof conditions Water vapour permeability + water resistance - working conditions - compatibility - tenting - blinding Installation Roof conditions : - 20 to C, 0 to 100% RH, seasonal, daily, hourly changes Compatibility Tenting - specifically with timber preservatives - water ( surfactants ) vs solvent based ( swelling ) cause loss of performance. - a problem with the early materials. Underlay leaks when touching surface below. Blinding - by dust, ice (?) Installation or - laid direct on insulation (common practice in North) - can cause noise (ie wind flutter )? - supported on counterbattens(common practice in South) - userfriendliness => slipperiness underfoot for roofer!

22 BATTENS Tiling, counter Dimensions Location of underlay Securement When the insulation is installed over the rafters, counter-battens will be required to secure the insulation to the rafters and to provide drainage under the tile battens - refer to BS 5534 Part 1 Section Care should be taken to ensure that the construction techniques employed provide for adequate and accurate location of the fixings used to secure the battens and counterbattens to the rafters. Width determined by diameter of fasteners (10-11 x diameter) Thickness determined by method of securement Underlay can be in direct contact with surface of insulation or located above the counter battens Who installs what? Carpenter - up to and including counterbattens (rafters, insulation) Roofer - above counterbattens (underlay, tile battens, tiles) or from the rafters up (insulation, battens, underlay,tiles)

23 SECUREMENT - need to secure tiles/slates, underlay and insulation against dead wind and imposed loads Insulation consider: - thickness (over rafters), physical properties Fasteners eg BS 1202 nails, Helifix Inskew, Proctor PR nails consider: - penetration, pull-out strength, deflection under load - ease and accuracy of installation Refer to manufacturers for advice

24 SECUREMENT cont When the insulation is installed over the rafters the fasteners securing the counter battens or battens through to the rafters must be of sufficient strength and length and correctly spaced so as to resist dead, wind and imposed loads. The following should be considered: Site locality - the assessment and determination of wind and imposed loads Roof Construction - roof pitch, rafter spacing, depth and width, insulation thickness; batten/counter batten length, width and depth; fastener diameter, length and spacing. Materials and related properties - slate/tile weight; rafter and battens/.counter battens: timber specification; fasteners: pull-out and pullthrough strengths, shear strength and deformation under load characteristics. Consideration should also be given to the deflection and possible overloading of the fasteners under load down the slope of the roof. It is recommended that the deflection should not exceed 3mm. A fastener must be capable of withstanding the dead and imposed loads vectored down the slope of the roof i.e its maximum allowable bending stress must not be exceeded - refer to the fastener and insulation manufacturers for advice. It may be necessary to provide stronger and larger diameter fasteners (with a corresponding increase in batten and rafter dimensions) or a reduced spacing and/or stop battens (i.e parallel to the eaves/ridge) Note : The trend towards increased thickness of insulation with reduced U values (June 2000 proposals to change Approved Document L).

25 Securement cont! BS 6399 : Part 1 : 1996 Deadloads! BS 6399 : Part 2 : 1995 Wind uplift! BS 6399 : Part 3 : 1988 Imposed Loads! BS 5268 : Part 2 : 1996! BS 5534 : Part 1 : 1997! BS 1202 : Part 1 : 1994 use above to determine fastener size and density ( per m 2 ) Note: Designers must take into account the two loading conditions for the fasteners: Wind uplift on the roof. Resistance to slip (deflection of the fastener) down the slope - dependant on the pitch of the roof and the dead and imposed loading. Insulation should not be considered to be a structural material. Refer to manufacturer s literature for the specialist fasteners.

26 Fasteners - method of securement Counter battens nailed to rafters through insulation Tile battens nailed to counter battens Tiles Rafter thickness Figure above shows a method of securement for insulation laid over and between the rafters, in this case Roofmate PR. Counterbattens 32 mm thick secured with galvanised slab nails 100mm long x 3.35 mm dia spaced at 200 and 150 mm centres for duo and mono pitched roofs respectively - refer to BS 5268 : Part 2 : Tiling battens are secured with galvanised slab nails at the required gauge - refer to BS 5534 : Part 1: 1997.

27 BUILDING REGULATIONS Building Regulations 1991, amended Requirement LI : Conservation of Fuel and Power Reasonable provision shall be made for the conservation of fuel and power in buildings by limiting the heat loss through the fabric of the building

28 BUILDING REGULATIONS Approved Document L Maximum U-values (W/m2K) DWELLINGS Approved Document L : 1995 U- values OTHER BUILDINGS SAP </= 60 >60 Cold roof Warm roof Cold roof 0.25 Warm roof - residential others 0.45 If roof slope is greater than 70 o then max U = 0.45 W/m 2 K For building classification see Approved Document B Building Regulations specify maximum allowable U-values - the optimum cost effective U-values are in fact lower eg: W/m 2 K Floors 0.35 Roofs Walls

29 BUILDING REGULATIONS CONDENSATION Approved Document F:1995 Adequate provision shall be made to prevent excessive condensation in a roof but. Is based on traditional underlay experience therefore.. refer to: BRE Thermal insulation : avoiding risks see Section Sarking insulation BS see Clauses 9.1, 9.2 and 9.3

30 CONDENSATION - it s prevention Short, long term concerns Insulation Underlay - continuity, convection tight, performance - choice, performance Roof covering (tiles/slates) - air permeability (?) Ventilation YES - between underlay/roof covering YES - between insulation/traditional underlay NO - between insulation/breather underlay Control of condensation is of particular concern for those roof systems where a breather underlay is used without a ventilated airspace between it and the insulation. It is recommended that a condensation risk analysis is undertaken - refer to to BS Use of the criteria for condensation build-up within the roof system as detailed in BS 6229 : 1982 (Section A ) is recommended. The roof system below a breather underlay should be designed and installed so as to be convection tight as is possible throughout its design life. Consideration should be given to installing a VCL on the warm side of insulation if the insulation has a low water vapour resistance - refer to the insulation manufacturer for advice. cont ->

31 For buildings with high internal temperatures and humidities it is recommended that a VCL be installed and for exceptional conditions, as may be experienced in say swimming pools, laundries, that the advice of a design specialist be sought. Ventilation - defined as the controlled movement of air There are two air spaces to be considered: Between the underlay and the insulation For traditional underlays ventilation should be provided in accordance with the recommendations given in BS 5250 and Approved Document F2 (1990). For breather underlays ventilation is not normally required. Between the roof covering and underlay Where a traditional underlay is used it is not normally necessary to provide ventilation. Where a breather underlay is used without ventilation between the underlay and insulation it will be necessary to ensure that there is adequate ventilation. This may be provided through the slate/tile assembly. Apertures for ventilation can be provided at the eaves, ridge or incorporated into the slate/tile assembly - refer to BS 5250 for ventilation aperture sizes. NOTE: Ventilation through the slate/tile joints may not be sufficient due to the close fitting of the slates/tiles. There may also be a risk that the joints become blocked by vegetation or dust over the lifespan of the roof. Additional ventilation inlets or outlets may, therefore, be required. Particular attention should be given to long span roofs to ensure that adequate ventilation is provided.

32 BUILDING REGULATIONS FIRE APPROVED DOCUMENT B : 1992 EXTERNAL FIRE SPREAD - B4 BS 476 : Part 3 : 1958 AA (best) rating - tile/slate roofs - unaffected by insulation INTERNAL FIRE SPREAD - B2 BS476 : Part 7 : 1971 Class O rating - 13mm plasterboard BS476 : Part 7 External fire exposure roof tests BS476 : Part 1 Surface spread of flame test - lists Classes 1 (highest) to 4; XPS is unclassifiable Class O is not identified in BS476. However, it can be achieved by materials of limited combustibility e.g plasterboard or a Class 1 material which has a fire propagation index (I) < 12 and a sub-index (I,) < 6. For useful information on aspects of XPS in building applications see BS 6203 : 1989

33 INSULATED PITCHED ROOFING In summary: Warm roof concept 15 + years proven track record minimal condensation problems secure Design for the total system Pay attention to the design of details* Take care in installation The issues: Insulation - location, selection, installation Underlay - selection, performance, installation Condensation - its prevention Securement * see end of tutorial for typical details

34 Case study - Hospital Extension m 2 insulated pitched roof Architects: Watkins, Gray International Main contractor: J Longley & Co. Insulation installer: NH Etheridge Ltd Roofer: Cobsen, Davies Location: Conquest Hospital, Hastings, East Sussex Project: BUPA extension - completed 1998

35 Case study - Hospital! Insulation: Roofmate* PR Type 50 (90mm)! Roof space for services - heating, ventilation

36 Case study - Hospital! Underlayer: Tyvek 2001-B Pro! Securement:! Tiles: (over counterbattens) Helifix Inscrew 600 fasteners - 110mm long Marley Modern

37 Case study - Hospital U-value calculations Tiles Vented airspace Tyvek 2001-B Pro Unvented airspace Roofmate PR Plasterboard U-value = 0.25 W/m 2 K Thickness Thermal Resistance (mm) (m2k/w) Outside surface resistance Concrete tiles Vented airspace (between tiles and sarking) Tyvek 2001-BPro - - Unvented airspace Roofmate PR Unvented airspace Plasterboard Inside surface resistance

38 Case study - Hospital Condensation risk analysis U-value: 0.25 W/m 2 K Condensation build up winter 0 g/m 2 summer 0 g/m 2 annual 0 g/m 2 Red : Actual temperature profile Blue : dew point temperature Temperature ºC Condensation occurs where red and blue lines touch or cross Notes: Element: Pitched roof, ceiling at rafter line, warm pitched roof Exposure: exposed Internal surface emissivity: high External surface emissivity: high Building use: hospital Environmental conditions Summer Winter Internal temp ºC External temp ºC 18 5 Internal humidity % External humidity % Construction Thickness (mm) Vapour Resistance (MNs/g) Outside surface resistance - - Concrete tiles Vented airspace - - (between tiles and sarking) Tyvek 2001-BPro Unvented airspace - - Roofmate PR Roofmate PR Umvented airspace - - Plasterboard Inside surface resistance - -

39 Warm pitched roof construction - detailing

40 Warm pitched roof construction Type A - insulation over and between rafters - Roofmate PR Counter battens Tiling battens Tiles Vapour permeable membrane Roofmate PR Insulation Rafter

41 A1- Eaves detail Ensure continuity of insulation Set rebated edges of insulation over rafters

42 A2 - Hip detail Cut insulation to line of hip and set over support battens Hip rafter

43 A3 - Roof window detail Roof window Cut insulation to fit tight against roof window trimmers and seal with gap filler Counter batten

44 A4 - Valley detail Discontinuous edge batten to allow drainage and ventilation Gutter lining on separating layer Cut insulation boards to line of valley. Form rebate to set over valley boards Set valley boards between rafters

45 A5 - Ridge detail Nail tiles to battens Nail tiling battens to counterbattens Nail counter battens to rafters Cut insulation to fit tight at ridge and seal with gap filler

46 A6 - Abutment detail Fix batten in gap between insulation and wall Insulation over and between rafters Underlay

47 A7 - Verge detail Insulation set over and between rafters Flying rafter Bargeboard

48 Warm pitched roof construction Type B - insulation over rafters Roofmate RL Counterbattens Tiling battens Tiles Vapour permeable membrane Roofmate RL Insulation Rafter

49 B1 - Eaves detail Ensure continuity of insulation

50 B2 - Hip detail Cut insulation to line of hip and set onto support battens Support battens Hip rafter

51 B3 - Roof window detail Roof window Cut insulation to fit tight against roof window trimmers and seal with gap filler Counter batten

52 B4 - Valley detail Cut insulation boards to line of valley and set over valley boards Discontinuous edge batten to allow drainage and ventilation Gutter lining on separating layer Valley rafter Set valley boards between rafters

53 B5 - Ridge detail Nail counterbattens to rafters Nail tiles to battens Nail tiling battens to counterbattens Cut insulation to fit tight at ridge and seal with gap filler

54 B6 - Abutment detail Nail counter battens to rafters Nail battens to counter battens Plasterboard ceiling Lay insulation boards over rafters

55 B7 - Verge detail Plasterboard ceiling Bargeboard Make up piece of insulation set over gable wall

56 INSULATED PITCHED ROOFING Summarising : Issues : Warm Roof: 15 years proven experience! minimal condensation, securement problems Design for total system Attention to detail design Care in installation Insulation selection, performance, installation Underlay selection, performance, installation Condensation: it s prevention Securement

57 If the following questionnaire is successfully completed and sent to Dow Construction Products, 2 Heathrow Boulevard, 284 Bath Road, West Drayton, Middx UB7 0DQ Fax Number a CPD certificate will be forwarded to you. 1. In the warm roof concept the insulation is placed above the rafters between the rafters above and between the rafters between the rafters 2. If a pitched roof is insulated at rafter level (and the loft space is to be utilised) What are the maximum allowable U-values Domestic Buildings (SAP>60) Non-Domestic - Old Peoples Home - Office 3. What is the difference between a traditional and breather underlay Water tight Air tight Tear Strength (nails) Tensile properties Water Vapour permeable 4. Where would you provide ventilation in a pitched roof construction insulated at rafter level if a) a traditional or b) a breather underlay is used? (a) (b) Below rafters Below insulation Between insulation and underlay Between underlay and tiles/slates

58 5. Which properties are of particular importance for breather underlays? Water resistance Water vapour resistance Compatibility with timber preservatives Tear strength Tearing resistance Slipperiness Blinding resistance Colour Air tightness 6. In designing a pitched roof which standards should you refer to for General design - slating/tiling Wind loads Design - timber structure Dead loads Imposed loads 1 = BS 6399 : Part 1 2 = BS 6399 : Part 2 3 = BS 6399 : Part 3 4 = BS 5534 : Part 1 5 = BS 5268 : Part 2

59 7. Where would you go for advice on how to avoid condensation in a pitched roof? BS 5250 Approved Document L Approved Document F BRE 262 Thermal Insulation : avoiding risks BS 5534 Insulation manufacturers 8. In a warm roof construction what issues did you need to consider to avoid/reduce the risk of condensation.? Use of a vapour control layer Water vapour permeability of insulation Convection tightness of insulation layer Type of underlay Location of underlay Where to ventilate Air permeability of primary roof covering Drying our of building structure Attention to details e.g. at eaves Securement of underlay 9. What factors must be considered when selecting and specifying fasteners? Length Diameter Pull-out strength (from timber) Bending stress Ease and accuracy of installation Deflection under load Width of battens, rafters

60 10. Which of these should be considered when selection of insulation for installation or rafter level? Location Compressive strength Rigidity Water vapour permeability Water resistance Thermal conductivity Ease of installation Fire resistance Nail ability Name Company Name Address Telephone Number