Limiting thermal bridging and air leakage: Robust construction details for dwellings and similar buildings. robust details

Transcription

1 DEFRA Department for Environment, Food & Rural Affairs DTLR TRANSPORT LOCAL GOVERNMENT REGIONS Limiting thermal bridging and air leakage: Robust construction details for dwellings and similar buildings. London: TSO

2 Published by TSO (The Stationery Office) and available from: Online Mail, Telephone, Fax & TSO PO Box 29. Norwich. NR3 IGN Telephone orders/general enquiries: Fax orders: Textphone TSO Shops 123 Kingsway, London WC2B 6PQ Fax Bull Street, Birmingham B4 6AD Fax Princess Street, Manchester M60 8AS Fax Arthur Street. Belfast BTI 4GD Fax The Stationery Office Oriel Bookshop High Street, Cardiff CFI 2BZ Fax Lothian Road. Edinburgh EH3 9AZ Fax TSO Accredited Agents (see Yellow Pages) and through good booksellers Queen s Printer and Controller of Her Majesty s Stationery Office, 2001 Copyright in the typographical arrangement rests with the Crown. The publication, excluding logos, maybe reproduced free of charge in any format or medium for research, private study or for internal circulation within an organisation. This is subject to it being reproduced accurately and not used in a misleading context. The material must be acknowledged as copyright of the Queen s Printer and Controller of Her Majesty s Stationery Office and the title of the publication specified. For any other use of this material, please write to Her Majesty s Stationery Office, The Copyright Unit, St Clements House, 2-16 Colegate, Norwich NR3 1BQ Fax: or copyright@hmso.gov.uk. This is a value added publication which falls outside the scope of the HMSO Class Licence. Printed in Great Britain on material containing 75% post-consumer waste and 25% ECF pulp. ISBN First Published 2001 Second impression (with amendments) 2002

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5 1 Limiting thermal bridging and air leakage: Robust construction details for dwellings and similar buildings.

6 Contents Introduction Section 1 Foreword Introduction 1.1 The need for Robust Details What are Robust Details? Where can they be used? Minimum insulation thicknesses at critical junctions Limitations of this guidance Alternative Details Terms and definitions 1.2 Acknowledgments 1.3 Masonry: External Wall Insulation Section 2 Masonry: Cavity Wall Insulation: Full-Fill Section 3 Masonry: Cavity Wall Insulation: Partial-Fill Section 4 Masonry: Internal Wall Insulation Section 5 Timber Frame Section 6 Light Steel Frame Section 7 General Arrangements Section 8

7 Foreword By Nick Raynsford Minister of State for Local Government and the Regions Pressing environmental issues mean that we must continually strive to make our buildings more energy efficient. With this comes the need to constantly review the way we build and to change our practices if necessary. That is why I attach such importance to the continued review of Part L of the Building Regulations, the recently published first stage of amendments and the future stages that are already under consideration. This Robust Details document will help the construction industry meet the new performance standards for thermal resistance and airtightness in the first stage amendment due to come into effect on 1 April I hope that it will stimulate manufacturers, suppliers and designers to develop their own details that improve still further on cost-effectiveness, practicality and the avoidance of condensation. It is right that we should help the construction industry to meet changing standards. Industry Advisory Groups have been a successful feature of this review, supporting the development of this document, and I am pleased that my Department and DEFRA have been able to respond to their calls. It is also right that the construction industry should work with those developing the new standards. This document is an exemplar of this mutual understanding with manufacturers, designers, builders and researchers working together for the benefit of the whole industry. I would like to thank the organisations and their representatives for their time and expertise. The construction details contained here have been rigorously analysed to confirm they are robust, if constructed with reasonable attention to workmanship and supervision. Their simplicity belies the time and effort I know has been invested in them. Whilst a collection of construction details will never be complete, this document provides the construction industry with a starting point that can be developed and improved as standards and construction practice continue to evolve. I commend it to you.

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9 1.1 Introduction The need for Robust Details This first edition of Robust Details has been prepared to assist the construction industry in achieving the performance standards published in the Building Regulations Approved Document L1 (2002 edition). They are intended to reduce risks and potential problems that can arise as a result of building to higher energy efficiency standards such as: interstitial condensation risk which can lead to the deterioration of the structure surface condensation risk which can lead to mould growth blockage of essential ventilation paths which can lead to condensation building up in places such as roof or floor voids risk of rain penetration higher heat loss than expected higher air leakage than expected leading to unforeseen but significant heat losses and occupant discomfort What are Robust Details? As standards change it is not always practical or technically advisable to simply adjust existing details to accommodate a greater thickness of insulation. Robust Details have been developed that: are based on existing industry practice use currently available materials and products are not sensitive to minor material substitutions are durable minimise the risk of surface and interstitial condensation should avoid excessive air leakage are readily buildable with available skills Where can they be used? This guidance is intended for dwellings built using the forms of construction covered by the details. It is also applicable to other buildings using these forms of construction so long as there is a domestic internal environment (e.g. it is not appropriate for high humidity rooms such as indoor swimming pools even in dwellings). Details are suitable for the elements with U-values in the following ranges: Element U-Value* Pitched Roof - insulation between rafters Pitched Roof - insulation between joists Flat roof Wall ** Floor * All U-values are calculated in accordance with the method specified in the Building Regulations Approved Document L1. ** Walls were assessed at the U-value originally proposed in the Part L Consultation Document. The details contained within this document may also be applied to situations where insulation levels are better than those given above, without increasing risk of greater air leakage and thermal bridging. However, specifiers should satisfy themselves that insulation thickness does not present any buildability issues. For details with insulation values worse than those given above, see section Alternative Details.

10 Introduction Insulation thicknesses to achieve any given U-value have not been provided as these depend on the thermal properties of the materials chosen. For calculation of U-values, specifiers should refer to the Approved Document L1, manufacturer s latest published figures and literature or other authoritative guidance. The details are not applicable to elements sheltered by an unheated space Minimum insulation thicknesses at critical junctions Certain parts of the external envelope are particularly prone to internal surface condensation risk. In these areas, it is important to provide a minimum thickness of insulation. Different insulation materials have different thermal properties (conductivities) and so different thicknesses of insulation are needed to achieve the same performance. For this reason R-values are used. The R- value is the thermal resistance and allows the thickness of insulation required to be calculated for a given material. To calculate the thickness of a given material thickness needed to achieve a given R-value, the following formula is used: t (mm) = R x λ x 1000 Where A = the required thermal resistance of the insulation in m 2 K/W λ = the thermal conductivity (lambda value) of the insulation in W/mK For ease of use, tables have been provided alongside relevant details showing thickness of insulation required for a range of common thermal conductivities. Example: for a given detail where insulation with a minimum R-value of 0.75m 2 K/W is required the following table would be provided. To achieve R=0.75m 2 K/W λ (W/mK) Thickness (mm) Limitations of this guidance Every effort has been made to ensure that the Robust Details do not conflict with the other technical requirements of Building Regulations at the time of publication. However, it remains the builder s responsibility to ensure that building work which follow Robust Details meets all aspects of the Building Regulations Alternative Details This guidance document considers a range of common construction details within a range of U- values. Other details, and where the U-values are worse than the range shown in can be used; BRE Information Paper IP 17/01 Assessing the effects of thermal bridging at junctions and around openings may be used as a means of assessing compliance in these situations.

11 1.2 Terms and definitions Dense Block For the purposes of Robust Details a dense block is one with with a thermal conductivity greater than 0.7W/mK. Insulating Block For the purposes of Robust Details a lightweight block is one with a thermal conductivity less than or equal to 0.2W/mK. Aircrete blocks would meet this requirement. Minimum Thermal Resistance Path For the purpose of assessing cavity closers, the minimum thermal resistance path is that path from internal surface to external surface that has the smallest thermal resistance, Rmin. For openings, the boundary, between the frame of the window or door and the opening, defines where the internal and external surfaces begin, i.e. at the lines of connection of frame to the opening. The minimum thermal resistance path is not necessarily the shortest path. Other, longer paths may exist, particularly where there are highly conductive materials. For thin layers not greater than 4mm thick and with thermal conductivity not greater than 0.3W/mK, the thermal conductivity, within and parallel to the thin layer, should be considered to be zero (i.e. infinite thermal resistance) while the thermal conductivity across the thickness of the thin layer is that of the layer itself. Provided the thermal conductivity of the shell of a cavity closer is not greater than 0.3W/mK, this means considering only the thickness of the shell in any possible minimum thermal resistance path and ignoring any path within and parallel to the sides of the shell. Thermal Conductivity (lambda - λ ) Thermal Conductivity is a measure of a material s ability to conduct heat. It is measured in W/mK and is the quantity of heat (in Watts) which will pass through, 1 square metre of the material 1 metre thick for each degree difference in temperature between one side of the material and the other. Any quoted thermal conductivity of a given material is, therefore, independent of its thickness. Thermal Resistance (R-value) The thermal resistance of a given thickness of a material is measured in m 2 K/W and is equal to the thickness of the material (in metres) divided by the thermal conductivity of that material. Surfaces and cavities also provide thermal resistance and there are standard figures for these resistances which must be taken into account when calculating U-values. The resistance of each material within an element are added together to determine the overall resistance of the element. Vapour Control Layers A vapour control layer (v.c.l.) is a material with a vapour resistance greater than 200 MNs/g. A v.c.l. is sometimes required on the warm side of the insulation, to reduce the possible risk of interstitial condensation within the insulation or on other surfaces within the construction. 500gauge (0.12mm) polythene would meet this requirement. Vapour Permeable Underlay A thin membrane with a vapour resistance not more than 0.25MNs/g used for restricting liquid water penetration whilst allowing water vapour transfer, e.g. as a tiling underlay.

12 1.3 Acknowledgments The DTLR would like to thank all those who participated in the development of this document. In particular we wish to thank the members of the Robust Details Working Panel and the Department s Part L Industry Advisory Groups for the time and effort that they have contributed. The DTLR also wishes to thank DEFRA for their support during the development of the document. Members of the Robust Details Working Panel Mr Norman Blower - Glass and Glazing Federation Mr Dennis Coward (Catnic) - Steel Lintel Manufacturers Association Dr Vic Crisp Building Research Establishment / Quantum Partnership (Chair) Mr Michael Driver - Brick Development Association Ltd Mr Cliff Fudge (H+H Celcon Ltd) - Autoclaved Aerated Concrete Products Association Ltd Mrs Sarah Greenwood - Building Research Establishment Dr Mark Gorgolewski - Steel Construction Institute Mr Steve Halcrow (Knauf) - Gypsum Product Development Association Mr Philip Heath (Kingspan Insulation Ltd) - British Rigid Urethane Foam Manufacturers Association Mr Ian Hornby (Redrow Group Plc) - House Builders Federation Mr Nick Jones - Building Research Establishment Mr Ted King - DTLR Mr Mervyn Kirk (Alumasc Exterior Building Products Ltd) - Insulated Render & Cladding Association Mr Phil Lever (Lignacite Ltd) - Concrete Block Association Mr Peter Lusby Taylor (HTA Architects) - Architects in Housing Mr John Mitchell - Zurich Municipal Mr Sam Patterson (Springvale EPS Ltd) - British Plastics Federation EPS Construction Group Mr John Pilkington (Owens Corning Building Products Ltd) - Eurisol Mr Fred Randall (Wilcon Homes Ltd) - House Builders Federation Mr Jerry Robson (Instafoam & Fibre Ltd) Council for Energy Efficiency Development Mr Keith Ross - Building Research Establishment Mr Chris Sanders - Building Research Establishment Mr David Scott The Timber & Brick Consortium Ltd Mr Neil Smith - NHBC Mr Chris Stride Federation of Environmental Trade Associations Mr Paul Wornell - Housing Association Property Mutual Any queries regarding Robust Details should be sent to Energy Helpdesk, Energy Division, BRE, Garston, Watford WD25 9XX, or helpdesk@robustdetails.co.uk

13 2Robust Details - Masonry: External Wall Insulation 2

14 Contents Introduction Section 1 Masonry: External Wall Insulation Section 2 Introduction 2.00 Pitched roof. Ventilated loft. Eaves Pitched roof. Ventilated loft. Gable Pitched roof. Ventilated rafter void. Eaves Pitched roof. Ventilated rafter void. Gable Pitched roof. Ventilated batten void (warm roof). Eaves Pitched roof. Ventilated batten void (warm roof). Gable Timber flat roof Timber flat roof with parapet Windows and doors. Lintel Windows and doors. Jambs and sills Ground bearing floor. Insulation above slab Ground bearing floor. Insulation below slab Raft foundation In-situ suspended ground floor slab. Insulation above slab In-situ suspended ground floor slab. Insulation below slab Precast concrete ground floor Timber suspended ground floor Separating wall Concrete intermediate floor Timber intermediate floor Masonry: Cavity Wall Insulation: Full-Fill Section 3 Masonry: Cavity Wall Insulation: Partial-Fill Section 4 Masonry: Internal Wall Insulation Section 5 Timber Frame Section 6 Light Steel Frame Section 7 General Arrangements Section 8 Masonry : External Wall Insulation

15 Introduction 2.00 Plaster or plasterboard Solid block wall (any type) Cladding (render finish shown) Externally applied insulation system (various fixing methods) The Robust Details shown here have been developed for a range of externally insulated solid masonry wall constructions. For this form of construction, details are given for the junctions with a range of roof, ground floor and internal floor types, in addition to details around window openings etc. Details that apply to all wall types and guidance on air leakage are included in section 8 General Arrangements. There are many types of insulating materials and masonry products and the details have, therefore, been assessed for any combination of insulation and masonry type which meet the calculated U- values given in section Unless otherwise stated on the particular detail, any type of concrete block or thermal insulation material can be used, providing they are suitable for their intended purpose. Insulation thicknesses for main building elements have not generally been provided as these depend on the thermal properties of the matenals chosen, together with the proposed U-value (which may vary if the Elemental Method of compliance is not used). For calculation of U-values, specifiers should refer to the Approved Document L1, manufacturer s latest published figures and literature, or other authoritative guidance. All details are shown with a thin coat render system for simplification. However, a range of cladding may be used without any loss of thermal performance or increased technical risk. These include thick coat renders, brick slips, tile hanging, and other proprietary systems. It is recommended that insulating and cladding components are part of a system to ensure compatibility. Masonry : External Wall Insulation

16 2.01 Pitched roof. Ventilated loft. Eaves. Detail Apply 50mm (min) layer of compressible mineral wool or similar (R=1.2m 2 K/W) over wall and ensure loft insulation meets wall insulation. 2. Use proprietary crossflow ventilator or ensure 25mm (min) air gap. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry : External Wall Insulation

17 Pitched roof. Ventilated loft. Gable Section through detail Place loft insulation between last truss and gable wall. This detail should be read in conjunction with detail Masonry : External Wall Insulation

18 2.03 Pitched roof. Ventilated rafter void. Eaves. Detail Tightly pack any gaps between wall insulation and roof insulation with mineral wool (or similar) to limit air leakage. 2. Use suitable cross flow ventilator and maintain 50mm (min) ventilation path over insulation. 3. Secondary insulation lining to u/s of rafter if required to achieve U-value. 4. Vapour control layer behind plasterboard. 5. Seal gap between floor and sloping ceiling. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry : External Wall Insulation

19 Pitched roof. Ventilated rafter void. Gable Section through detail Level top of gable wall with mortar to correct pitch. 2. Wall insulation should be taken up level with top of gable wall. 3. Use mineral wool strip (or similar) compressed between top of gable and underside of sarking felt to prevent thermal bridge and limit air leakage. 4. Maintain 50mm (min) ventilation path over insulation. 5. Secondary insulation lining to u/s of rafter if required to achieve U-value. 6. Vapour control layer behind plasterboard. 7. Rafter. This detail should be read in conjunction with detail Masonry : External Wall Insulation

20 2.05 Pitched roof. Ventilated batten void (warm roof). Eaves. Detail Tightly pack gap between wall insulation and roof insulation with mineral wool (or similar) to limit air leakage. 2. Support insulation between rafters on battens or clips (or fully fill rafter void). 3. Vapour permeable underlay under counter battens. 4. Vapour control layer. 5. Seal gap between floor and sloping ceiling. 6. Maintain ventilation to batten void. 7. Eaves carrier. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry : External Wall Insulation

21 Pitched roof. Ventilated batten void (warm roof). Gable Section through detail Level top of gable wall with mortar to correct pitch. 2. Wall insulation should be taken up level with top of gable wall. 3. Use mineral wool strip compressed between top of gable and underside of sarking insulation to prevent thermal bridge and limit air leakage. 4. Ensure insulation is placed between gable wall and last rafter. 5. Insulation between rafters supported on battens or clips (or fully fill rafter void). 6. Vapour permeable underlay under counterbattens. 7. Vapour control layer. 8. Maintain ventilation to batten void. 9. Rafter. This detail should be read in conjunction with detail Masonry: External Wall Insulation

22 2.07A Timber flat roof. 1. Eaves - Fix full height blocking piece and tightly pack mineral wool into void and under deck. Verge - Tightly pack mineral wool into void over wall and under deck (not shown). 2. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. Finishing details may vary according to covering type. Roof falls provided by firrings of tilting joists (not shown). Rev A ( ) Vapour control layer amended to lap with roof waterproofing layer Masonry: External Wall Insulation

23 Timber flat roof with parapet. 2.08A To achieve R=0.75m 2 K/W (note 1) λ* (W/mK) Tickness (mm) Place strip of insulation with minimum R-value of 0.75m 2 K/W around parapet - see table. 2. Minimum distance 300mm between top of edge insulation and bottom of roof insulation. 3. Impervious cladding. 4. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. 5. Flashing (150mm minimum above finish roof level). Finishing details may vary according to covering type. Roof falls provided by firrings of tilting joists (not shown). * Thermal conductivity Rev A ( ) Vapour control layer amended to lap with roof waterproofing layer Masonry: External Wall Insulation

24 2.09 Windows and doors. Lintel. To achieve R=0.5m 2 K/W (note 2) λ* (W/mK) Tickness (mm) Lintel can be of any type. 2. Wall insulation with a minimum R-value of 0.5m 2 K/W should overlap the window frame/packing piece - see table. Ensure that trickle vents are not obstructed or provide alternative arrangement for ventilation. 3. Sealant to front and back of frame. 4. Optional packing piece. * Thermal conductivity Masonry: External Wall Insulation

25 Windows and doors. Jambs and sills Plan view Achieve R=0.5m 2 K/W (note 1) * (W/mK) Thickness (mm) Wall insulation with a minimum R-value of 0.5m 2 K/W should overlap the window frame/packing piece - see table. 2. Wall insulation to be carried up to under side of sill. 3. Sealant to front and back of frame/sill. 4. Optional packing piece. The use of closers, minimum overlaps and sealants also apply to junctions between external walls and bay windows/conservatories. For level threshold details see section 8 General Arrangements. * Thermal conductivity Masonry: External Wall Insulation

26 2.11 Ground bearing floor. Insulation above slab. To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Continue wall insulation at least 200mm below top of floor insulation (or perimeter insulation where screed is used). 2. Course may be split to assist tamping. 3. Vapour control layer under timber floor finish. 4. DPM may be above or below slab. Any screed must have an edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. * Thermal conductivity Masonry: External Wall Insulation

27 Ground bearing floor. Insulation below slab To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Continue wall insulation at least 200mm below top of perimeter insulation. 2. Perimeter insulation with minimum R-value of 0.75m 2 K/W - see table. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown). * Thermal conductivity Masonry: External Wall Insulation

28 2.13 Raft foundation. To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Continue wall insulation at least 200mm below top of perimeter insulation (or floor insulation where screed is omitted). 2. Any screed must have perimeter insulation with a minimum R-value of 0.75m 2 K/W - see table. 3. Course may be split depending on floor insulation thickness and to assist tamping. * Thermal conductivity Masonry: External Wall Insulation

29 In situ suspended ground floor slab. Insulation above slab To achieve R=0.75 m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Continue wall insulation at least 200mm below top of floor insulation (or perimeter insulation where screed is used). 2. Vapour control layer under timber floor finish. Any screed must have edge insulation with minimum R-value of 0.75m 2 MN (not shown) - see table. * Thermal conductivity Masonry: External Wall Insulation

30 2.15 In-situ suspended ground floor slab. Insulation below slab. To achieve R=0.75m 2 K/W (note 3) λ * Thickness (W/mK) (mm) Continue wall insulation at least 200mm below top of perimeter insulation. 2. Dense blocks should not be used below slab (coursing not shown). 3. Perimeter insulation with minimum R-value of 0.75m 2 K/W - see table. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown). * Thermal conductivity Masonry: External Wall Insulation

31 Precast concrete ground floor To achieve R=0.75m 2 K/W (see notes) λ * Thickness (W/mK) (mm) Continue wall insulation at least 200mm below top of floor insulation (or perimeter insulation where screed is used). 2. Vapour control layer under timber floor finish. 3. Ventilated sub-floor (vents not shown). Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. Alternative arrangements for DPC and DPM may be used. * Thermal conductivity Masonry: External Wall Insulation

32 2.17 Timber suspended ground floor. To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Insulation should be placed directly under timber flooring avoiding any air gaps and supported either (la) on battens (rigid insulation) or (1 b) on netting draped over joists and stapled at required depths (non rigid insulation). 2. Fix strip of insulation with minimum R-value of 0.75m 2 K/W between wall and last joist - see table. 3. To limit air leakage careful attention should be given to sealing around perimeter of floor by applying expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing. 4. Wall insulation must continue a minimum of 200mm below top of floor insulation. 5. Timber joists should be supported using joist hangers. 6. Ventilated sub-floor (vents not shown). 7. Render. Joist and joist hangers should be supported in line with BRE Good Building Guide 21 Joist hangers. * Thermal conductivity Masonry: External Wall Insulation

33 Separating wall Plan view Refer to Approved Document B for fire safety requirements relating to separating walls. Refer to Approved Document E for sound insulation requirements relating to separating walls and their associated flanking constructions. Masonry: External Wall Insulation

34 2.19 Concrete intermediate floor. 1. Continue wall insulation across floor zone. 2. Ensure gaps between wall and floor are sealed with split course infil blocks or full depth edge block (beam and block floors), or with dry non compressible mix (pre-stressed slabs). Separating/compartment floors may require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. Masonry: External Wall Insulation

35 Timber intermediate floor Timber joists should be supported using joist hangers. Joist and joist hangers should be supported in line with BRE Good Building Guide 21 Joist hangers. Separating/compartment floors require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. Masonry: External Wall Insulation

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37 3Robust Details - Masonry: Cavity Wall Insulation: Full-Fill 3

38 Contents Introduction Section 1 Masonry: External Wall Insulation Section 2 Masonry: Cavity Wall Insulation: Full-Fill Section 3 Introduction 3.00 Pitched roof. Ventilated loft. Eaves Pitched roof. Ventilated loft. Gable Pitched roof. Ventilated rafter void. Eaves Pitched roof. Ventilated rafter void. Gable Pitched roof. Ventilated batten void (warm roof). Eaves Pitched roof. Ventilated batten void (warm roof). Gable Timber flat roof Timber flat roof with parapet Windows and doors. Lintel Windows and doors. Folded lintel Windows and doors. Independent lintel Windows and doors. Jambs and sills Ground bearing floor. Insulation above slab Ground bearing floor. Insulation below slab Raft foundation In-situ suspended ground floor slab. Insulation above slab In-situ suspended ground floor slab. Insulation below slab Precast concrete ground floor Timber suspended ground floor Separating wall Concrete intermediate floor Timber intermediate floor Masonry: Cavity Wall Insulation: Partial-Fill Section 4 Masonry: Internal Wall Insulation Section 5 Timber Frame Section 6 Light Steel Frame Section 7 General Arrangements Section 8 Masonry: Cavity Wall Insulation: Full-Fill

39 Introduction 3.00 Plaster or plasterboard Block wall inner leaf (any type) Full-fill cavity wall insulation Outer leaf (brick shown) The Robust Details shown here have been developed for a range of fully filled cavity wall constructions. For this form of construction, details are given for the junctions with a range of roof, ground floor and internal floor types, in addition to details around window openings etc. Details which apply to all wall types and guidance on air leakage are included in section 8 General Arrangements. There are many types of insulating materials and masonry products and the details have, therefore, been assessed for any combination of insulation and masonry type which meet the calculated U-values given in section Unless otherwise stated on the particular detail, any type of concrete block or thermal insulation material can be used providing they are suitable for their intended purpose. Insulation thicknesses for main building elements have not generally been provided as these depend on the thermal properties of the materials chosen, together with the proposed U-value (which may vary if the Elemental Method of compliance is not used). For calculation of U-values, specifiers should refer to the Approved Document L1, manufacturer s latest published figures and literature, or other authoritative guidance. All details are shown with a brick outer leaf for simplification. However, other types of masonry materials may be used as a substitution, without any loss of thermal performance or increased technical risk - such as blockwork with render, tile hanging or weather boarding. The suitability of this form of construction is dependent on the exposure of the site and the nature of the outer leaf. Further information is given in BR262 Thermal Insulation: Avoiding Risks, NHBC Standards, and Zurich Building Guarantees Technical Manual. Masonry: Cavity Wall Insulation: Full-Fill

40 3.01 Pitched roof. Ventilated loft. Eaves. Detail Apply 50mm (min) layer of compressible mineral wool or similar (R=1.2m 2 K/W) over wall and ensure loft insulation meets wall insulation. 2. Use proprietary crossflow ventilator or ensure 25mm (min) air gap. Fire stopping may be required with some wall insulation materials. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Full-Fill

41 Pitched roof. Ventilated loft. Gable Section through detail Place loft insulation between last truss and gable wall. 2. Continue wall insulation to top of gable or alternatively stop wall insulatio n 250mm above bottom of ceiling tie and insert cavity tray. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Full-Fill

42 3.03 Pitched roof. Ventilated rafter void. Eaves. Detail Tightly pack any gaps between wall insulation and roof insulation with mineral wool (or similar) to limit air leakage. 2. Use suitable cross flow ventilator and maintain 50mm (min) ventilation path over insulation. 3. Secondary insulation lining to u/s of rafter if required to achieve U-value. 4. Vapour control layer behind plasterboard. 5. Seal gap between floor and sloping ceiling. Fire stopping may be required with some wall insulation materials. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Full-Fill

43 Pitched roof. Ventilated rafter void. Gable Section through detail Level top of gable wall with mortar to correct pitch. 2. Wall insulation should be taken up level with top of gable wall. 3. Use mineral wool strip (or similar) compressed between top of gable and underside of sarking felt to prevent thermal bridge and limit air leakage. 4. Maintain 50mm (min) ventilation path over insulation. 5. Secondary insulation lining to u/s of rafter if required to achieve U-value. 6. Vapour control layer behind plasterboard. 7. Rafter. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Full-Fill

44 3.05 Pitched roof. Ventilated batten void (warm roof). Eaves. Detail Tightly pack gap between wall insulation and roof insulation with mineral wool (or similar) to limit air leakage. 2. Support insulation between rafters on battens or clips (or fully fill rafter void). 3. Vapour permeable underlay under counterbattens. 4. Vapour control layer. 5. Seal gap between floor and sloping ceiling. 6. Maintain ventilation to batten void. 7. Eaves carrier. Fire stopping may be required with some wall insulation materials. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail 3.06 Masonry: Cavity Wall Insulation: Full-Fill

45 Pitched roof. Ventilated batten void (warm roof). Gable Section through detail Level top of gable wall with mortar to correct pitch. 2. Wall insulation should be taken up level with top of gable wall. 3. Use mineral wool strip compressed between top of gable and underside of sarking insulation to prevent thermal bridge and limit air leakage. 4. Ensure insulation is placed between gable wall and last rafter. 5. Insulation between rafters supported on battens or clips (or fully fill rafter void). 6. Vapour permeable underlay under counterbattens. 7. Vapour control layer. 8. Maintain ventilation to batten void. 9. Rafter. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Full-Fill

46 3.07A Timber flat roof. 1. Eaves - Fix full height blocking piece and tightly pack mineral wool into void and under deck. Verge - Tightly pack mineral wool into void over wall and under deck (not shown). 2. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. Finishing details may vary according to covering type. Roof falls provided by firrings of tilting joists (not shown). Rev A ( ) Vapour control layer amended to lap with roof waterproofing layer Masonry: Cavity Wall Insulation: Full-Fill

47 Timber flat roof with parapet. 3.08A To achieve R=0 75m 2 K/W (note 1)1 λ * Thickness (W/mK) (mm) Place strip of insulation with minimum R-value of 0.75m 2 K/W around parapet - see table. 2. Minimum distance 300mm between top of edge insulation and bottom of roof insulation. 3. Impervious cladding. 4. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. 5. Flashing (150mm minimum above finish roof level). Finishing details may vary according to covering type. Roof falls provided by firrings of tilting joists (not shown). * Thermal cond uctivity Rev A ( ) Vapour control layer amended to lap with roof waterproofing layer Masonry: Cavity Wall Insulation: Full-Fill

48 3.09 Windows and doors. Lintel. Alternative for lintels with continuous steel baseplates To achieve R=0.34m 2 K/W (note 2) λ * Thickness (W/mK) (mm) Perforated baseplate with effective conductivity not exceeding 30W/mK (manufacturer s certified data). 2. For lintels with continuous solid steel baseplates soffit should be lined with insulation of minimum R-value of 0.34m 2 K/W -see table (alternative provision for trickle ventilation may be required). 3. Sealant to front and back of frame. Separate cavity trays may be required depending on exposure and lintel specification. * Thermal conductivity Masonry: Cavity Wall Insulation: Full-Fill

49 Windows and doors. Folded lintel Alternative for lintels with continuous steel baseplates To achieve R=0.34m 2 K/W (note 2) λ* Thickness (W/mK) (mm) No baseplate or perforated baseplate with effective conductivity not exceeding 30W/mK (manufacturer s certified data). 2. For lintels with continuous solid steel baseplates soffit should be lined with insulation of minimum R-value of 0.34m 2 K/W -see table (alternative provision for trickle ventilation may be required). 3. Sealant to front and back of frame. Separate cavity trays may be required depending on exposure and lintel specification. * Thermal conductivity Masonry: Cavity Wall Insulation: Full-Fill

50 3.11 Windows and doors. Independent lintel. 1. Any lintel types can be used. 2. Insulation ball brought down to window opening and cavity closed. 3. Cavity trays must have minimum upstand of 140mm and stop ends. 4. Sealant to front and back of frame. Masonry: Cavity Wall Insulation: Full-Fill

51 Windows and doors. Jambs and sills Plan view 1. Proprietary closer with minimum thermal resistance path of 0.45m 2 K/W (manufacturer s certified data). 2. Minimum frame/closer overlap: Exposure zones Sheltered - Severe* - 30mm. Exposure zones Very Severe* - Fully rebated (check reveals). Render or other impervious cladding should be used. 3. Sealant to front and back of frame/sills. The use of closers, minimum overlaps and sealants also apply to junctions between external walls and bay windows/conservatories. For level threshold details see section 8 General Arrangements. * As given in BR262 Thermal Insulation : Avoiding Risks, NHBC Standards, and Zurich Building Guarantees Technical Manual. Masonry: Cavity Wall Insulation: Full-Fill

52 3.13 Ground bearing floor. Insulation above slab. To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor insulation (or perimeter insulation where screed is used) and support on a row of ties. 2. Course may be split to assist tamping. 3. Vapour control layer under timber floor finish. 4. DPM may be above or below slab. Any screed must have an edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. * Thermal conductivity Masonry: Cavity Wall Insulation: Full-Fill

53 Ground bearing floor. Insulation below slab To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of perimeter insulation and support on row of ties. 2. Perimeter insulation with minimum R-value of 0.75m 2 K/W - see table. Any screed must have perimeter insulation with a minimum R-value of 0.75m 2 K/W (not shown). * Thermal conductivity Masonry: Cavity Wall Insulation: Full-Fill

54 3.15 Raft foundation. To achieve R=0.75m 2 K/W (note 2) λ * Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of perimeter insulation (or floor insulation where screed is omitted) and support on a row of ties. 2. Any screed must have perimeter insulation with a minimum R-value of 0.75m 2 K/W - see table. 3. Course may be split depending on floor insulation thickness and to assist tamping. Alternatively blockwork may be built off top of raft. * Thermal conductivity Masonry: Cavity Wall Insulation: Full-Fill

55 In-situ suspended ground floor slab. Insulation above slab To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor insulation (or perimeter insulation where screed is used) and support on a row of ties. 2. Vapour control layer under timber floor finish. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. * Thermal conductivity Masonry: Cavity Wall Insulation: Full-Fill

56 3.17 In-situ suspended ground floor slab. Insulation below slab. To achieve R=0.75m 2 K/W (note 3) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of perimeter insulation. 2. Dense blocks should not be used below slab (coursing not shown). 3. Perimeter insulation with minimum R-value of 0.75m 2 K/W - see table. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown). * Thermal conductivity Masonry: Cavity Wall Insulation: Full-Fill

57 Precast concrete ground floor To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor insulation (or perimeter insulation where screed is used) and support on a row of ties. 2. Vapour control layer under timber floor finish. 3. Ventilated sub-floor (vents not shown). Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. Alternative arrangements for DPC and DPM may be used. * Thermal conductivity Masonry: Cavity Wall Insulation: Full-Fill

58 3.19 Timber suspended ground floor. To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Insulation should be placed directly under timber flooring avoiding any air gaps and supported either (1a) on battens (rigid insulation) or, (1b) on netting draped over joists and stapled at required depths (non rigid insulation). 2. Fix strip of insulation with minimum R-value of 0.75m 2 K/W between wall and last joist - see table. 3. To limit air careful attention should be given to sealing around perimeter of floor by applying expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing. 4. Wall insulation must continue a minimum of 150mm below top of floor insulation and be supported on a row of ties. 5. Timber joists should be supported using joist hangers. 6. Ventilated sub-floor (vents not shown). Joist and joist hangers should be supported in line with BRE Good Building Guide 21 Joist hangers. * Thermal conductivity Masonry: Cavity Wall Insulation: Full-Fill

59 Separating wall Plan view Refer to Approved Document B for fire safety requirements relating to separating walls. Refer to Approved Document E for sound insulation requirements relating to separating walls and their associated flanking constructions. Masonry: Cavity Wall Insulation: Full-Fill

60 3.21 Concrete intermediate floor. 1. Continue wall insulation across floor zone. 2. Ensure gaps between wall and floor are sealed with split course infil blocks or full depth edge block (beam and block floors), or with dry non compressible mix (pre-stressed slabs). Separating/compartment floors may require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. Masonry: Cavity Wall Insulation: Full-Fill

61 Timber intermediate floor Timber joists should be supported using joist hangers. Joist and joist hangers should be supported in line with BRE Good Building Guide 21 Joist hangers. Separating/compartment floors require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. Masonry: Cavity Wall Insulation: Full-Fill

62 Masonry: Cavity Wall Insulation: Full-Fill

63 Robust Details - Masonry: Cavity Wall Insulation: Partial-Fill 4

64 Contents Introduction Section 1 Masonry: External Wall Insulation Section 2 Masonry: Cavity Wall Insulation: Full-Fill Section 3 Masonry: Cavity Wall Insulation: Partial-Fill Section 4 Introduction 4.00 Pitched roof. Ventilated loft. Eaves Pitched roof. Ventilated loft. Gable Pitched roof. Ventilated rafter void. Eaves Pitched roof. Ventilated rafter void. Gable Pitched roof. Ventilated batten void (warm roof). Eaves Pitched roof. Ventilated batten void (warm roof). Gable Timber flat roof Timber flat roof with parapet Windows and doors. Lintel Windows and doors. Folded lintel Windows and doors. Independent lintel Windows and doors. Jambs and sills Ground bearing floor. Insulation above slab Ground bearing floor. Insulation below slab Raft foundation In-situ suspended ground floor slab. Insulation above slab In-situ suspended ground floor slab. Insulation below slab Precast concrete ground floor Timber suspended ground floor Separating wall Concrete intermediate floor Timber intermediate floor Masonry: Internal Wall Insulation Section 5 Timber Frame Section 6 Light Steel Frame Section 7 General Arrangements Section 8 Masonry: Cavity Wall Insulation: Partial-Fill

65 Introduction 4.00 Plaster or plasterboard Block inner leaf (any type) Partial-fill cavity wall insulation (any type) retained against inner leaf Outer leaf (brick shown) 50mm residual cavity The Robust Details shown here have been developed for a range of partially filled cavity wall constructions. For this form of construction, details are given for the junctions with a range of roof, ground floor and internal floor types, in addition to details around window openings etc.. Details that apply to all wall types and guidance on air leakage are included in section 8 - 'General Arrangements. There are many types of insulating materials and masonry products and the details have, therefore, been assessed for any combination of insulation and masonry type which meet the calculated U-values given in section Unless otherwise stated on the particular detail, any type of concrete block or thermal insulation material can be used providing they are suitable for their intended purpose. Insulation thicknesses for main building elements have not generally been provided as these depend on the thermal properties of the materials chosen, together with the proposed U-value (which may vary if the Elemental Method of compliance is not used). For calculation of U- values, specifiers should refer to the Approved Document L1 or the manufacturer s latest published figures and literature, or other authoritative guidance. All details are shown with a brick outer leaf for simplification. However, other types of masonry materials may be used as a substitution, such as blockwork with render, tile hanging or weather boarding, without any loss of thermal performance or increased technical risk. Masonry: Cavity Wall Insulation: Partial-Fill

66 4.01 Pitched roof. Ventilated loft. Eaves. Detail Apply 50mm (min) layer of compressible mineral wool or similar(r=1.2m 2 K/W) over wall and ensure loft insulation meets wall insulation. 2. Use proprietary crossflow ventilator or ensure 25mm (min) air gap. 3. Fully close cavity with mineral wool or calcium silicate board (shown). This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Partial-Fill

67 Pitched roof. Ventilated loft. Gable Section through detail Place loft insulation between last truss and gable wall. 2. Continue wall insulation to top of gable or alternatively stop wall insulation 250mm above bottom of ceiling tie. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Partial-Fill

68 4.03 Pitched roof. Ventilated rafter void. Eaves. Detail Tightly pack any gaps between wall insulation and roof insulation with mineral wool (or similar) to limitair leakage. 2. Use suitable cross flow ventilator and maintain 50mm (min) ventilation path over insulation. 3. Secondary insulation lining to u/s of rafter if required to achieve U-value. 4. Vapour control layer behind plasterboard. 5. Seal gap between floor and sloping ceiling. 6. Fully close cavity with calcium silicate board or mineral wool closer (shown). Compliance with Approved Document B should be checked with wall insulation manufacturer. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Partial-Fill

69 Pitched roof. Ventilated rafter void. Gable.4.04 Section through detail Level top of gable wall with mortar to correct pitch. 2. Wall insulation should be taken up level with top of gable wall. 3. Use mineral wool strip (or similar) compressed between top of gable and underside of sarking felt to close cavity, prevent thermal bridge and limit air leakage. 4. Maintain 50mm (min) ventilation path over insulation. 5. Secondary insulation lining to u/s of rafter if required to achieve U-value. 6. Vapour control layer behind plasterboard. 7. Rafter. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Partial-Fill

70 4.05 Pitched roof. Ventilated batten void (warm roof). Eaves. Detail Tightly pack gap between wall insulation and roof insulation with mineral wool (or similar) to limit air leakage. 2. Support insulation between rafters on battens or clips (or fully fill rafter void). 3. Vapour permeable underlay under counterbattens. 4. Vapour control layer. 5. Fully close cavity with mineral wool or calcium silicate board (shown). 6. Maintain ventilation to batten void. 7. Seal gap between floor and sloping ceiling. 8. Eaves carrier. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Partial-Fill

71 Pitched roof. Ventilated batten void (warm roof). Gable Section through detail Level top of gable wall with mortar to correct pitch. 2. Wall insulation should be taken up level with top of gable wall. 3. Use mineral wool strip compressed between top of gable and underside of sarking insulation to close cavity, prevent thermal bridge and limit air leakage. 4. Ensure insulation is placed between gable wall and last rafter. 5. Insulation between rafters supported on battens or clips (or fully fill rafter void). 6. Vapour permeable underlay under counterbattens. 7. Vapour control layer. 8. Maintain ventilation to batten void. 9. Rafter. This detail should be read in conjunction with detail Masonry: Cavity Wall Insulation: Partial-Fill

72 4.07A Timber flat roof. 1. Eaves - Fix full height blocking piece and tightly pack mineral wool into void and under deck. Verge - Tightly pack mineral wool into void over wall and under deck (not shown). This will also have the effect of closing the cavity pack. 2. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. Finishing details may vary according to covering type. Roof falls provided by firrings of tilting joists (not shown). Rev A ( ) Vapour control layer amended to lap with roof waterproofing layer. Masonry: Cavity Wall Insulation: Partial-Fill

73 Timber flat roof with parapet. 4.08A To achieve R=0.75m 2 K/W (note 1) λ* Thickness (W/mK) (mm) Place strip of insulation with minimum R-value of 0.75m 2 K/W around parapet - see table. 2. Minimum distance 300mm between top of edge insulation and bottom of roof insulation. 3. Impervious cladding. 4. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. 5. Flashing (150mm minimum above finish roof level). Finishing details may vary according to covering type. Roof falls provided by firrings of tilting joists (not shown). * Thermal conductivity Rev A ( ) Vapour control layer amended to lap with roof waterproofing layer Masonry: Cavity Wall Insulation: Partial-Fill

74 4.09 Windows and doors. Lintel. Alternative for lintels with continuous steel baseplates To achieve R=0.34m 2 K/W (note 2) lambda Thickness (W/mK) (mm) Perforated baseplate with effective conductivity not exceeding 30W/mK (manufacturer s certified data). 2. For lintels with continuous solid steel baseplates soffit should be lined with insulation of minimum R-value of 0.34m 2 K/W -see table (alternative provision for trickle ventilation may be required). 3. Sealant to front and back of frame. Separate cavity trays may be required depending on exposure and lintel specification. * Thermal conductivity Robust details Masonry: Cavity Wall Insulation: Partial-Fill

75 Windows and doors. Folded lintel Alternative for lintels with continuous steel baseplates To achieve R=0.34m 2 K/W (note 2) λ* Thickness (W/mK) (mm) No baseplate or perforated baseplate with effective conductivity not exceeding 30W/mK (manufacturer s certified data). 2. For lintels with continuous solid steel baseplates soffit should be lined with insulation of minimum R-value of 0.34m 2 K/W (alternative provision for trickle ventilation may be required). 3. Sealant to front and back of frame. Separate cavity trays may be required depending on exposure and lintel specification. * Thermal conductivity Masonry: Cavity Wall Insulation: Partial-Fill

76 4.11 Windows and doors. Independent lintel. Alternative arrangement with Insulation inserted from below 1. Any lintel types can be used. 2. Insulation batt brought down to window opening and cavity closed. 3. Cavity trays must have minimum upstand of 140mm and stop ends. 4. Sealant to front and back of frame. Masonry: Cavity Wall Insulation: Partial-Fill

77 Windows and doors. Jambs and sills Plan view 1. Proprietary closer with minimum thermal resistance path of 0.45m 2 K/W (manufacturer s certified data). 2. Minimum frame/closer overlap: Exposure zones Sheltered - Severe* - 30mm. Exposure zones Very Severe* - Fully rebated (check reveals). 3. Sealant to front and back of frame/sills. The use of closers, minimum overlaps and sealants also apply to junctions between external walls and bay windows/conservatories. For level threshold details see section 8 General Arrangements. * As given in BR262 Thermal Insulation : Avoiding Risks, NHBC Standards, and Zurich Building Guarantees Technical Manual. Masonry: Cavity Wall Insulation: Partial-Fill

78 4.13 Ground bearing floor. Insulation above slab. To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor insulation (or perimeter insulation where screed is used) and support on a row of ties. 2. Course may be split to assist tamping. 3. Vapour control layer under timber floor finish. 4. DPM may be above or below slab. Any screed must have an edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. * Thermal conductivity Masonry: Cavity Wall Insulation: Partial-Fill

79 Ground bearing floor. Insulation below slab To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of perimeter insulation and support on row of ties. 2. Perimeter insulation with minimum R-value of 0.75m 2 K/W - see table. Any screed must have perimeter insulation with a minimum R-value of 0.75m 2 K/W (not shown). * Thermal conductivity Masonry: Cavity Wall Insulation: Partial-Fill

80 4.15 Raft foundation. To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of perimeter insulation (or floor insulation where screed is omitted) and support on row of ties. 2. Any screed must have perimeter insulation with a minimum R-value of 0.75m 2 K/W - see table. 3. Course may be split depending on floor insulation thickness, and to assist tamping. Alternatively blockwork may be built off top of raft. * Thermal conductivity Masonry: Cavity Wall Insulation: Partial-Fill

81 In-situ suspended ground floor slab. Insulation above slab To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor insulation (or perimeter insulation where screed is used) and support on a row of ties. 2. Vapour control layer under timber floor finish. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown) see table. * Thermal conductivity Masonry: Cavity Wall Insulation: Partial-Fill

82 4.17 In-situ suspended ground floor slab. Insulation below slab. To achieve R=0.75m 2 K/W (note 3) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of perimeter insulation. 2. Dense blocks should not be used below slab (coursing not shown). 3. Perimeter insulation with minimum R-value of 0.75m 2 KW - see table. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown). * Thermal conductivity Masonry: Cavity Wall Insulation: Partial-Fill

83 Precast concrete ground floor To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor insulation (or perimeter insulation where screed is used) and support on a row of ties. 2. Vapour control layer under timber floor finish. 3. Ventilated sub-floor (vents not shown). Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. Alternative arrangements for DPC and DPM may be used. * Thermal conductivity Masonry: Cavity Wall Insulation: Partial-Fill

84 4.19 Timber suspended ground floor. To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Insulation should be placed directly under timber deck avoiding any air gaps and supported either (1a) on battens (rigid insulation) or, (1b) on netting draped over joists and stapled at required depths (non rigid insulation). 2. Fix strip of insulation with minimum R-value of 0.75m 2 K/W between wall and last joist - see table. 3. To limit air leakage careful attention should be given to sealing around perimeter of floor by applying expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing. 4. Wall insulation must continue a minimum of 150mm below top of floor insulation and be supported on a row of ties. 5. Timber joists should be supported using joist hangers. 6. Ventilated sub-floor (vents not shown). Joist and joist hangers should be supported in line with BRE Good Building Guide 21 Joist hangers. * Thermal conductivity Masonry: Cavity Wall Insulation: Partial-Fill

85 Separating wall Plan view Refer to Approved Document B for fire safety requirements relating to separating walls. Refer to Approved Document E for sound insulation requirements relating to separating walls and their associated flanking constructions. Masonry: Cavity Wall Insulation: Partial-Fill

86 4.21 Concrete intermediate floor. 1. Continue wall insulation across floor zone. 2. Ensure gaps between wall and floor are sealed with split course infil blocks or full depth edge block (beam and block floors), or with dry non compressible mix (pre-stressed slabs). Separating/compartment floors may require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. Masonry: Cavity Wall Insulation: Partial-Fill

87 Timber intermediate floor Timber joists should be supported using joist hangers. Joist and joist hangers should be supported in line with BRE Good Building Guide 21 Joist hangers. Separating/compartment floors require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. Masonry: Cavity Wall Insulation: Partial-Fill

88

89 5 Robust Details - Masonry: Internal Wall Insulation 5

90 Contents Introduction Section 1 Masonry: External Wall Insulation Section 2 Masonry: Cavity Wall Insulation: Full-Fill Section 3 Masonry: Cavity Wall Insulation: Partial-Fill Section 4 Masonry: Internal Wall Insulation Section 5 Introduction 5.00 Pitched roof. Ventilated loft. Eaves Pitched roof. Ventilated loft. Gable Pitched roof. Ventilated rafter void. Eaves Pitched roof. Ventilated rafter void. Gable Pitched roof. Ventilated batten void (warm roof). Eaves Pitched roof. Ventilated batten void (warm roof). Gable Timber flat roof Timber flat roof with parapet Windows and doors. Lintel Windows and doors. Folded lintel Windows and doors. Jambs and sills Ground bearing floor. Insulation above slab Ground bearing floor. Insulation below slab Raft foundation In-situ suspended ground floor slab. Insulation above slab Precast concrete ground floor Timber suspended ground floor Separating wall Concrete intermediate floor Timber intermediate floor Timber Frame Section 6 Light Steel Frame Section 7 General Arrangements Section 8 Masonry: Internal Wall Insulation

91 Introduction 5.00 Insulated dry-lining (75mm max) on dabs or mechanical fixing Block wall inner leaf (any type) Outer leaf (brick shown) 50mm clear cavity The Robust Details shown here have been developed for a range of internally insulated cavity wall constructions. For this form of construction, details are given for the junctions with a range of roof, ground floor and internal floor types, in addition to details around window openings etc.. Details that apply to all wall types and guidance on air leakage are included in section 8 General Arrangements. There are many types of insulating materials and masonry products and the details have, therefore, been assessed for any combination of insulation and masonry type which meet the calculated U-values given in section Unless otherwise stated on the particular detail, any type of concrete block or thermal insulation material can be used providing they are suitable for their intended purpose. Insulation thicknesses for main building elements have not generally been provided as these depend on the thermal properties of the materials chosen, together with the proposed U-value (which may vary if the Elemental Method of compliance is not used). For calculation of U-values, specifiers should refer to the Approved Document L1, manufacturer s latest published figures and literature, or other authoritative guidance. Due to the practicality of fixing insulated dry lining to blockwork these details limit the overall board/insulation thickness to 75mm. All details are shown with a brick outer leaf for simplification. However, other types of masonry materials may be used as a substitution, such as blockwork with render, tile hanging or weather boarding, without any loss of thermal performance or increased technical risk. Masonry: Internal Wall Insulation

92 5.01 Pitched roof. Ventilated loft. Eaves. Detail Apply 50mm (min) layer of compressible mineral wool or similar (R=1.2m 2 K/W) over wall. 2. Use proprietary crossflow ventilator or ensure 25mm (min) air gap. 3. Apply continuous ribbon of adhesive to perimeter of wall. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry: Internal Wall Insulation

93 Pitched roof. Ventilated loft. Gable Section through detail Place loft insulation between last truss and gable wall. 2. Apply continuous ribbon of adhesive to perimeter of wall. This detail should be read in conjunction with detail Masonry: Internal Wall Insulation

94 5.03 Pitched roof. Ventilated rafter void. Eaves. Detail Tightly pack any gaps between wall insulation and roof insulation with mineral wool (or similar) to limit air leakage. 2. Use suitable cross flow ventilator and maintain 50mm (min) ventilation path over insulation. 3. Secondary insulation lining to u/s of rafter if required to achieve U-value. 4. Vapour control layer behind plasterboard. 5. Seal gap between floor and sloping ceiling. 6. Apply continuous ribbon of adhesive to perimeter of wall. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry: Internal Wall Insulation

95 Pitched roof. Ventilated rafter void. Gable Section through detail Level top of gable wall with mortar to correct pitch. 2. Use mineral wool strip (or similar) compressed between top of gable and underside of sarking felt to close cavity, prevent thermal bridge and limit air leakage. 3. Maintain 50mm (min) ventilation path over insulation. 4. Secondary insulation lining to u/s of rafter if required to achieve U-value. 5. Vapour control layer behind plasterboard. 6. Apply continuous ribbon of adhesive to perimeter of wall. 7. Rafter. This detail should be read in conjunction with detail Masonry: Internal Wall Insulation

96 5.05 Pitched roof. Ventilated batten void (warm roof). Eaves. Detail Tightly pack gap between wall insulation and roof insulation with mineral wool (or similar) to limit air leakage. 2. Support insulation between rafters on battens or clips (or fully fill rafter void). 3. Vapour permeable underlay under counter battens. 4. Vapour control layer. 5. Seal gap between floor and sloping ceiling. 6. Maintain ventilation to batten void. 7. Eaves carrier. 8. Apply continuous ribbon of adhesive to perimeter of wall. Seal gap between floor and sloping ceiling. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Masonry: Internal Wall Insulation

97 Pitched roof. Ventilated batten void (warm roof). Gable Section through detail Level top of gable wall with mortar to correct pitch. 2. Use mineral wool strip compressed between top of gable and underside of sarking insulation to close cavity, prevent thermal bridge and limit air leakage. 3. Ensure insulation is placed between gable wall and last rafter. 4. Insulation between rafters supported on battens or clips (or fully fill rafter void). 5. Vapour permeable underlay under counter battens. 6. Vapour control layer. 7. Maintain ventilation to batten void. 8. Apply continuous ribbon of adhesive to perimeter of wall. 9. Rafter. This detail should be read in conjunction with detail Masonry: Internal Wall Insulation

98 5.07A Timber flat roof. 1. Eaves - Fix full height blocking piece and tightly pack mineral wool into void and under deck. Verge - Tightly pack mineral wool into void over wall and under deck (not shown). This will also have the effect of closing the cavity. 2. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. 3. Apply continuous ribbon of adhesive to perimeter of wall. Finishing details may vary according to covering type. Roof falls provided by firrings of tilting joists (not shown). Masonry: Internal Wall Insulation

99 Timber flat roof with parapet. 5.08A To achieve R=0.75m 2 K/W (note1) λ* Thickness (W/mK) (mm) Place strip of insulation with minimum R-value of 0.75m 2 K/W against wall held in place by joist (verge) or battens (eaves) - see table. 2. Impervious cladding. 3. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. 4. Apply continuous ribbon of adhesive to perimeter of wall. 5. Flashing (150mm minimum above finish roof level) Finishing details may vary according to covering type. Roof falls provided by firrings of tilting joists (not shown). Rev A ( ) Vapour control layer amended to lap with roof waterproofing layer Masonry: Internal Wall Insulation

100 5.09 Windows and doors. Lintel. To achieve R=0.34m 2 K/W (note 1) λ* Thickness (W/mK) (mm) Insulate soffit with insulation of minimum R-value of 0.34m 2 K/W (alternative provision for trickle ventilation may be required) - see table. 2. Sealant to front and back of frame. 3. Apply continuous ribbon of adhesive to perimeter of opening. Separate cavity trays may be required depending on exposure and lintel specification. * Thermal conductivity Masonry: Internal Wall Insulation

101 Windows and doors. Folded lintel To achieve R=0.34m 2 K/W (note 1) λ * Thickness (W/mK) (mm) Insulate soffit with insulation of minimum R-value of 0.34m 2 K/W (alternative provision for trickle ventilation may be required) - see table. 2. Sealant to front and back of frame. 3. Apply continuous ribbon of adhesive to perimeter of opening. Separate cavity trays may be required depending on exposure and lintel specification. * Thermal conductivity Masonry: Internal Wall Insulation

102 5.11 Windows and doors. Jambs and sills. Plan view To achieve R=0.34m 2 K/W (note 1) λ* Thickness (W/mK) (mm) Reveals to be insulated with insulation of minimum R-value of 0.34m 2 K/W - see table. 2. Proprietary closer with minimum thermal resistance path of 0.45m 2 K/W (manufacturer s certified data). 3. Minimum frame/closer overlap: Exposure zones Sheltered - Severe** - 30mm. Exposure zones Very Severe** - Fully rebated (check reveals). 4. Sealant to front and back of frame/sills. 5. Apply continuous ribbon of adhesive to perimeter of opening. The use of closers, minimum overlaps and sealants also apply to junctions between external walls and bay windows/conservatories. For level threshold details see section 8 General Arrangements. Foot note * Thermal conductivity ** As given in BR262 Thermal Insulation : Avoiding Risks, NHBC Standards, and Zurich Building Guarantees Technical Manual. Masonry: Internal Wall Insulation

103 Ground bearing floor. Insulation above slab To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Apply continuous ribbon of adhesive to perimeter of wall. 2. Apply expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing to reduce air leakage. 3. Course may be split to assist tamping. 4. Vapour control layer under timber floor finish. 5. DPM may be above or below slab. Any screed must have an edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. * Thermal conductivity Masonry: Internal Wall Insulation

104 5.13 Ground bearing floor. Insulation below slab. To achieve R=0.75m 2 K/W (note 1) λ* Thickness (W/mK) (mm) Perimeter insulation with minimum R-value of 0.75m 2 K/W - see table. 2. Apply continuous ribbon of adhesive to perimeter of wall. 3. Apply expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing to reduce air leakage. Any screed must have an edge insulation with minimum R-value of 0.75m 2 K/W (not shown). Masonry: Internal Wall Insulation

105 Raft foundation To achieve R=0.75m 2 K/W λ* Thickness (W/mK) (mm) Any screed must have perimeter insulation with a minimum R-value of 0.75m 2 K/W - see table. 2. Apply continuous ribbons of adhesive to perimeter. 3. Apply expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing to reduce air leakage. 4. Courses may be split depending on floor insulation thickness and to assist tamping. Alternatively blockwork may be built off top of raft. * Thermal conductivity Masonry: Internal Wall Insulation

106 5.15 In-situ suspended ground floor slab. Insulation above slab. To achieve R=0.75m 2 K/W (see notes) λ * Thickness (W/mK) (mm) Apply continuous ribbon of adhesive to perimeter of wall. 2. Apply expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing to reduce air leakage. 3. Vapour control layer under timber floor finish. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. * Thermal conductivity Masonry: Internal Wall Insulation

107 Precast concrete ground floor To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Apply continuous ribbon of adhesive to perimeter of wall. 2. Apply expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing to reduce air leakage. 3. Vapour control layer under timber floor finish. 4. Ventilated sub-floor (vents not shown). Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. Alternative arrangements for DPC and DPM may be used. * Thermal conductivity Masonry: Internal Wall Insulation

108 5.17 Timber suspended ground floor. To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Insulation should be placed directly under timber deck avoiding any air gaps and supported either; (1a) on battens (rigid insulation) or, (1b) on netting draped over joists and stapled at required depths (non rigid insulation). 2. Place strip of insulation with minimum R-value of 0.75m 2 K/W between wall and last joist - see table. 3. To limit air leakage careful attention should be given to sealing around perimeter of floor. Close gap between wall insulation and floor with non-adhesive gap filler, or apply expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing. 4. Apply continuous ribbon of adhesive to perimeter of wall. 5. Timber joists should be supported using joist hangers. 6. Ventilated sub-floor (vents not shown). Joist and joist hangers should be supported in line with BRE Good Building Guide 21 Joist hangers. * Thermal conductivity Masonry: Internal Wall Insulation

109 Separating wall Plan view 1. Cavity barrier should be a minimum of 260mm wide or the width of the party wall (which ever is greater). Refer to Approved Document B for fire safety requirements relating to separating walls. Refer to Approved Document E for sound insulation requirements relating to separating walls and their associated flanking constructions. Masonry: Internal Wall Insulation

110 5.19 Concrete intermediate floor. To achieve R=1.25m 2 K/W (note 1) λ* Thickness (W/mK) (mm) Place insulation of minimum R-value 1.25m 2 K/W in cavity projecting 100mm above and below floor zone - see table. 2. Ensure gaps between wall and floor are sealed with split course infil blocks or full depth edge block (beam and block floors), or with dry non compressible mix (pre stressed slabs). 3. Apply expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing to reduce air leakage. 4. Insulating blocks for whole inner leaf. 5. Apply continuous ribbons of adhesive to perimeter of walls. Separating/compartment floors may require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. Footnote * Thermal conductivity ** As given in BR262 Thermal Insulation Avoiding Risks NHBC Standards and Zurich Building Guarantees Technical Manual Masonry: Internal Wall Insulation

111 Timber intermediate floor Section through joist To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Timber joists should be supported using joist hangers. 2. Place insulation with minimum R-value of 0.75m 2 K/W against wall held in place by joist or battens - see table. 3. Apply expanding foam tape under skirting and continuous bead of sealant to back of skirting prior to fixing to reduce air leakage. 4. Apply continuous ribbon of adhesive to perimeter of walls. Joist and joist hangers should be supported in line with BRE Good Building Guide 21 Joist hangers. Separating/compartment floors may require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. * Thermal conductivity Masonry: Internal Wall Insulation

112

113 6 Robust Details - Timber Frame 6

114 Contents Introduction Section 1 Masonry: External Wall Insulation Section 2 Masonry: Cavity Wall Insulation: Full-Fill Section 3 Masonry: Cavity Wall Insulation: Partial-Fill Section 4 Masonry: Internal Wall Insulation Section 5 Timber Frame Section 6 Introduction 6.00 Pitched roof. Ventilated loft. Eaves Pitched roof. Ventilated loft. Gable Pitched roof. Ventilated rafter void. Eaves Pitched roof. Ventilated rafter void. Gable Pitched roof. Ventilated batten void (warm roof). Eaves Pitched roof. Ventilated batten void (warm roof). Gable Timber flat roof Timber flat roof with parapet Windows and doors. Independent lintel Windows and doors. Jambs and sills Ground bearing floor. Insulation above slab Ground bearing floor. Insulation below slab Raft foundation In-situ suspended ground floor slab. Insulation above slab Precast concrete ground floor Timber suspended ground floor Separating wall Timber intermediate floor Wall junction Light Steel Frame Section 7 General Arrangements Section 8 Timber Frame

115 Introduction 6.00 Plasterboard Vapour control layer Structural timber frame Insulation Sheathing board Stainless steel wall tie Key to membranes used in this section Sarking felt Vapour control layers DPM/DPC Vapour permeable underlay/breather membrane Waterproof breather membrane External cladding (brick shown) Cavity The Robust Details drawn here are valid for a range of timber frame wall thicknesses from 89mm up to 150mm stud size. For this form of construction, details are given for the junctions with a range of roof, ground floor and internal floor types, in addition to details around window openings etc.. Details that apply to all wall types and guidance on air leakage are included in section 8 General Arrangements. The nature of timber framed construction is that a variety of structural forms can be adopted, with variables such as stud centres, double or single head plates. The form of structure selected has an influence on the thermal performance of any given wall and so must be taken into account by those using these details. Further variables are: type of insulation chosen type of sheathing type and thickness of plasterboard (or other sheet material) internal linings used and the outer cladding of the building. Products specified should be suitable for their intended purpose. Insulation thicknesses for main building elements have not generally been provided as these depend on the thermal properties of the materials chosen together with the proposed U-value (which may vary if the Elemental Method of compliance is not used). For calculation of U-values specifiers should refer to the Approved Document L1, or the manufacturer s latest published figures and literature, or other authoritative guidance. All details are shown with a brick outer leaf for simplification. However, other types of claddings may be used without any loss of thermal performance or increased technical risk subject to suitable detailing. These include render on metal lath (on vertical battens fixed direct to frame), tile hanging on battens on frame, sheet panel systems on vertical counter battens fixed to frame, outer leaf of other masonry. Note that the detailing of the outer skin will vary and attention is drawn to relevant technical guidance on the subject, in particular Timber Frame Construction published by TRADA. Timber Frame

116 6.01 Pitched roof. Ventilated loft. Eaves. Detail Ensure 50mm (min) layer of compressible mineral wool or similar (R=1.2m 2 K/W) fully covers top of wall panel. 2. Use proprietary crossflow ventilator or ensure 25mm (min) air gap. 3. Cavity barrier. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail See 6.00 for key to membranes. Timber Frame

117 Pitched roof. Ventilated loft. Gable Section through detail Continue loft insulation up to sheathing of spandrel panel. 2. Cavity barrier (alternatively may follow line of verge). This detail should be read in conjunction with detail See 6.00 for key to membranes. Timber Frame

118 6.03 Pitched roof. Ventilated rafter void. Eaves. Detail Tightly pack any gaps between wall insulation and roof insulation with mineral wool (or similar) to limit air leakage. 2. Use suitable cross flo w ventilator and maintain 50mm (min) ventilation path over insulation. 3. Secondary insulation lining to u/s of rafter if required to achieve U-value. 4. Vapour control layer behind plasterboard. 5. Cavity barrier. 6. Seal gap between floor and sloping ceiling. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail See 6.00 for key to membranes. Timber Frame

119 Pitched roof. Ventilated rafter void. Gable Section through detail 6.03 Differential movement gap (note 6) Floor Ground floor type number Timber Other (detail 6.16) 1st 8mm 6mm 2nd 15mm 12mm 3rd 21mm 18mm 1. Tightly pack mineral wool or similar between top of gable panel and underside of sarking felt prior to roofing to prevent thermal bridge and limit air leakage. 2. Maintain 50mm (min) ventilation path over insulation. 3. Secondary insulation lining to u/s of rafter if required to achieve U-value. 4. Vapour control layer behind plasterboard. 5. Cavity barrier. 6. Differential movement gap (see table) sealed with compressible foam or sealant. This detail should be read in conjunction with detail See 6.00 for key to membranes. Timber Frame

120 6.05 Pitched roof. Ventilated batten void (warm roof). Eaves. Detail Tightly pack gap between wall insulation and root insulation with mineral wool or similar to limit air leakage. 2. Support insulation between rafters on battens or clips (or fully fill rafter void). 3. Vapour permeable underlay under counter battens. 4. Vapour control layer (may be omitted if condensation risk assessment shows not required). 5. Maintain ventilation to batten void. 6. Seal gap between floor and sloping ceiling. 7. Cavity barrier. 8. Eaves carrier. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail See 6.00 for key to membranes. Timber Frame

121 Pitched roof. Ventilated batten void (warm roof). Gable Section through detail 6.05 Differential movement gap (note 6) Floor Ground floor type number Timber Other (detail 6.16) 1st 2nd 3rd 8mm 15mm 21mm 6mm 12mm 18mm 1. Tightly pack mineral wool or similar between top of gable panel and underside of sarking insulation prior to roofing to prevent thermal bridge and limit air leakage. 2. Support insulation between rafters on battens or clips (or fully fill rafter void). 3. Vapour permeable underlay under counterbattens. 4. Vapour control layer (may be omitted if condensation risk assessment shows not required). 5. Cavity barrier. 6. Differential movement gap (see table) sealed with compressible foam or sealant. 7. Maintain ventilation to batten void. This detail should be read in conjunction with detail See 6.00 for key to membranes. Timber Frame

122 6.07A Timber flat roof. Differential movement gap (note 4) Floor Ground floor type number Timber Other (detail 6.16) 1st 2nd 3rd 8mm 15mm 21mm 6mm 12mm 18mm 1. Eaves Fix full height blocking piece and tightly pack mineral wool into void and under deck. Verge - Tightly pack mineral wool into void over wall and under deck (not shown). 2. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. 3. Cavity barrier. 4. Differential movement gap (see table) sealed with compressible foam sealant. 5. D.P.C. tray. See 6.00 for key to membranes. Rev A ( ) Vapour control layer amended to lap with roof waterproofing layer Timber Frame

123 Timber flat roof with parapet. 6.08A Differential movement gap (note 5) Floor Ground floor type number Timber Other (detail 6.16) 1 st 8mm 6mm 2 nd 15mm 12mm 3 rd 21mm 18mm 1. Wall insulation continued to top of wall panel. 2. Firrings (falls may also be provided by tilting joists). 3. Vapour control layer turned up edge of roof insulation, lapped with roof waterproofing layer, and sealed. Ensure compatible materials are used. 4. Cavity barrier. 5. Differential movement gap (see table). 6. Flashing (1 50mm minimum above finish roof level). Roof finishing details may vary according to covering type. See 6.00 for key to membranes. Rev A ( ) Vapour control layer amended to lap with roof waterproofing layer Timber Frame

124 6.09 Windows and doors. Independent lintel. Alternative tor heavy duty lintel To achieve R=0.34m 2 K/W (note 6) λ* Thickness (W/mK) (mm) Standard duty steel lintel. 2. Cavity closer (treated softwood batten or proprietary closer). 3. Return breather membrane under closer and turn into window head. 4. Ensure that vapour control layer (or vapour control grade plasterboard) is returned into reveal. 5. Sealant to front and back of frame. 6. For heavy duty steel lintels (alternative detail) internal soffit should be lined with insulation of minimum R-value of 0.34m 2 K/W (alternative provision for trickle ventilation may be required) - see table. See 6.00 for key to membranes. * Thermal conductivity Timber Frame

125 Windows and doors. Jambs and sills Differential movement gap (note 5) Ground floor type Openings on: Timber (detail 6.16) Other Ground floor 5mm 3mm 1 st floor 12mm 9mm 2 nd floor 18mm 15mm 1. Either: proprietary closer with minimum thermal resistance path of 0.45m 2 K/W (manufacturer s certified data), or, treated softwood batten. 2. DPC fitted to jamb/cill (timber closers). 3. Minimum frame/closer overlap: Exposure zones Sheltered - Severe* - 30mm. Exposure zones Very Severe* - Fully rebated (check reveals). 4. Sealant to front and back of frame/sills (see note 5). 5. Differential movement gap (see table) sealed with compressible foam or sealant. The use of closers, minimum overlaps and sealants also apply to junctions between external walls and bay windows/conservatories. For level threshold details see section 8 General Arrangements. See 6.00 for key to membranes. * As given in BR262 Thermal Insulation : Avoiding Risks, NHBC Standards, and Zurich Building Guarantees Technical Manual. Timber Frame

126 6.11 Ground bearing floor. Insulation above slab. Alternative with screed To achieve R=0.75m 2 K/W (note 4) λ* Thickness (W/mK) (mm) Ensure DPC turns up behind sole plates and laps with vertical vapour control layer to improve airtightness. (Alternatively apply bead of sealant to DPC prior to fixing sole plate.) 2. Vapour control layer under timber floor finish. 3. DPM may be above or below slab. 4. Any screed must have an edge insulation with minimum R-value of 0.75m 2 K/W (alternative detail) - see table. See 6.00 for key to membranes. * Thermal conductivity Timber Frame

127 Ground bearing floor. Insulation below slab To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Ensure DPCturns up behind sole plates and laps with vertical vapour control layer to improve airtightness. (Alternatively apply bead of sealant to DPC prior to fixing sole plate.) 2. Floor slab perimeter insulation with minimum R-value of 0.75m 2 K/W - see table. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (not shown). See 6.00 for key to membranes. * Thermal conductivity Timber Frame

128 6.13 Raft foundation. Alternative with screed To achieve R=0.75m 2 K/W (note 3) λ* Thickness (W/mK) (mm) Ensure DPC turns up behind sole plates and laps with vertical vapour control layer to improve airtightness. (Alternatively apply bead of sealant to DPC prior to fixing sole plate.) 2. Vapour control layer under timber floor finish. 3. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (alternative detail) - see table. See 6.00 for key to membranes. * Thermal conductivity Timber Frame

129 In-situ suspended ground floor slab. Insulation above slab Alternative with screed To achieve R=0.75m 2 K/W (note 3) λ* Thickness (W/mK) (mm) Ensure DPC turns up behind sole plates and laps with vertical vapour control layer to improve airtightness (Alternatively apply bead of sealant to DPC prior to fixing sole plate.) 2. Vapour control layer under timber floor finish. 3. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (alternative detail) - see table. See 6.00 for key to membranes. * Thermal conductivity Timber Frame

130 6.15 Precast concrete ground floor. Alternative detail with screed To achieve R=0 75m 2 K/W (note 4) λ * Thickness (W/mK) (mm) Ensure DPC turns up behind sole plates and laps with vertical vapour control layer to improve airtightness. (Alternatively apply bead of sealant to DPC prior to fixing sole plate.) 2. Vapour control layer under timber floor finish. 3. Ventilated sub-floor (vent not shown). 4. Any screed must have edge insulation with minimum R-value of 0.75m 2 K/W (alternative detail) - see table. Alternative arrangements for DPC and DPM may be used. See 6.00 for key to membranes. * Thermal conductivity Timber Frame

131 Timber suspended ground floor Insulation should be placed directly under timber deck avoiding any air gaps and supported either; (1a) on battens (rigid insulation) or (1b) on netting draped over joists and stapled at required depths (non rigid insulation). 2. Apply bead of sealant prior to positioning wall panel. 3. Ventilated sub-floor minimum 150mm (vent not shown). See 6.00 for key to membranes. Timber Frame

132 6.17 Separating wall. Plan view 1. Alternative locations for acoustic insulation mm wire reinforced mineral wool fire stop. 3. Alternative corner details - see detail Refer to Approved Document B for fire safety requirements relating to separating walls. Refer to Approved Document E for sound insulation requirements relating to separating walls and their associated flanking constructions. See 6.00 for key to membranes. Timber Frame

133 Timber intermediate floor To achieve R=0.75m 2 K/W (note 1) λ * Thickness (W/mK) (mm) a. Insulation with minimum R-value of 0.75m 2 K/W placed around floor perimeter. 1b. Alternative position. (Additional support may be required depending on rigidity of material) - see table. 2. Apply PVC gasket or bead of sealant on floor deck prior to positioning upper wall panel. Separating/compartment floors require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. See 6.00 for key to membranes. * Thermal conductivity Timber Frame

134 6.19 Wall junction. 1. Standard detail - insulation tucked into corner. 2. Alternative detail where required for structural reasons - insulation must be placed in void before wall panels are erected. See 6.00 for key to membranes. Timber Frame

135 7 Robust Details - Light Steel Frame 7

136 Contents Introduction Section 1 Masonry: External Wall Insulation Section 2 Masonry: Cavity Wall Insulation: Full-Fill Section 3 Masonry: Cavity Wall Insulation: Partial-Fill Section 4 Masonry: Internal Wall Insulation Section 5 Timber Frame Section 6 Light Steel Frame Section 7 Introduction 7.00 Pitched roof. Ventilated loft. Eaves Pitched roof. Ventilated loft. Gable Pitched roof. Ventilated batten void (warm roof). Eaves Pitched roof. Ventilated batten void (warm roof). Gable Windows and doors. Independent lintel Windows and doors. Jambs and sills Ground bearing floor. Insulation above slab Ground bearing floor. Insulation below slab Raft foundation In-situ suspended ground floor slab. Insulation above slab Precast concrete ground floor Separating wall Lightweight intermediate floor General Arrangements Section 8 Light Steel Frame

137 Introduction 7.00 Plasterboard Light steel studs Insulated sheathing board with foil face (shown) or breather membrane External cladding Warm frame construction (brick shown) Cavity Wall ties Vapour control layer Hybrid construction Insulation between and outside of structural steel Insulated sheathing board with foil face or breather membrane (shown) This section shows appropriate details for light steel frame construction. With this form of construction it is important that some insulation is placed outside the steel frame to provide a thermal break and avoid condensation. Two basic types are covered: Warm frame construction where all the insulation is outside the steel frame. Hybrid construction, where insulation is included both outside the steel structure and in between the steel components (a minimum of 33% of the thermal resistance should be provided outside the steel). With this form of construction a condensation risk analysis (in accordance with BS 5250) should be provided by the system manufacturer to ensure there is no risk of interstitial condensation. An internal vapour control layer is generally required. The details drawn in this section are based on warm frame construction but apply equally to hybrid construction. Details that apply to all wall types and guidance on air leakage are included in section 8 General Arrangements. The depth of steel frame can typically vary from 75 mm to 150 mm and these details are appropriate for all such variations. Insulation thicknesses have generally not been shown as these depend on the thermal properties of materials. However, it is important that appropriate tightly fitting materials are chosen. Generally, a rigid insulation material is required outside the frame that acts as an insulated sheathing board. Where the hybrid construction is used, with some insulation between the frame, a vapour control layer should be provided unless careful condensation risk analysis shows that this is not necessary. For both types, air tightness may be achieved by insulation boards with lapped joints or by sealing joints e.g. with tape approved by insulation manufacturer. Good seals should be ensured at junctions particularly with the ground floor. A vapour control layer can act as an additional air barrier. For calculation of u-values specifiers should refer to U-value calculation procedure for light steel walls, BRE (to be published), or the manufacturer s latest published figures and literature. Although the drawn details all show brickcladding, they are appropriate for a range of other claddings subject to suitable detailing. Light Steel Frame

138 7.01 Pitched roof. Ventilated loft. Eaves. Detail Apply 50mm (min) layer of compressible mineral wool or similar(r=1.2m 2 K/W) over wall and ensure loft insulation meets wall insulation. 2. Use proprietary crossflow ventilator or ensure 25mm (min) air gap. 3. Vapour control layer - not required with timber rafters. 4. Cavity barrier. Compliance with Approved Document B should be checked with wall insulation manufacturer. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Light Steel Frame

139 Pitched roof. Ventilated loft. Gable Section through detail Continue loft insulation up to outside of gable panel. 2. Wall insulation continued to top of gable panel or stopped a minimum of 250mm above bottom of ceiling tie. Alternative verge arrangements may be used. 3. Vapour control layer - not required with timber rafters. 4. Cavity barrier. Compliance with Approved Document B should be checked with wall insulation manufacturer. This detail should be read in conjunction with detail Light Steel Frame

140 7.03 Pitched roof. Ventilated batten void (warm roof). Eaves. Detail Care should be taken to ensure insulation is carefully cut and continued around boxed eaves. All cut joints should be sealed with tape approved by insulation manufacturer. Fixing details of insulation and facia may vary. Insulation should have same R-value as wall sheathing. 2. Maintain ventilation to batten void. 3. Vapour permeable underlay under counterbattens. 4. Seal gap between floor and sloping ceiling. 5. Mineral wool (or similar) packed into eaves limits air leakage and fully closes steel wall panel. 6. Eaves carrier. This detail is also suitable for monopitch roofs subject to suitable ventilation provision. This detail should be read in conjunction with detail Light Steel Frame

141 Pitched roof. Ventilated batten void (warm roof). Gable.7.04 Section through detail Care should be taken to ensure insulation is carefully cut and continued around wall/roof junction. All cut joints should be sealed with tape approved by insulation manufacturer. 2. Maintain ventilation to batten void. 3. Vapour permeable underlay under counter battens. 4. Cavity barrier. Compliance with Approved Document B should be checked with wall insulation manufacturer. This detail should be read in conjunction with detail Light Steel Frame

142 7.05 Windows and doors. Independent lintel Alternative for heavy duty lintel. To achieve R=0.34m 2 K/W (note 4) λ* Thickness (W/mK) (mm) Standard duty steel lintel. 2. Cavity closer (treated softwood batten or proprietary closer). 3. Sealant to front and back of frame. 4. For heavy duty steel lintels (see alternative detail) internal soffit should be lined with insulation of minimum R-value of 0.34 m 2 K/W (alternative provision for ventilation may be required) - see table. * Thermal conductivity Light Steel Frame

143 Windows and doors. Jambs and sills Plan view 1. Either: proprietary closer with minimum thermal resistance path of 0.45m 2 K/W manufacturer s certified data), or, treated softwood batten. 2. Minimum frame/closer overlap: Exposure zones Sheltered - Severe* - 30mm. Exposure zones Very Severe* - Fully rebated (check reveals). 3. Sealant to front and back of frame/internal sills. The use of closers, minimum overlaps and sealants also apply to junctions between external walls and bay windows/conservatories. For level threshold details see section 8 General Arrangements. * As given in BR262 Thermal Insulation : Avoiding Risks, NHBC Standards, and Zurich Building Guarantees Technical Manual. Light Steel Frame

144 7.07 Ground bearing floor. Insulation above slab. To achieve R=0.75m 2 K/W (note 3) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor insulation (or perimeter insulation where screed is used). 2. Insulating block must be used under steel wall panel. Course may be split to assist tamping. 3. Vapour control layer under timber floor finish. Alternatively a screed can be used with edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. 4. DPM may be above or below slab. * Thermal conductivity Light Steel Frame

145 Ground bearing floor. Insulation below slab To achieve R=0.75m 2 K/W (note 3) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of perimeter insulation. 2. Insulating block must be used under steel wall panel. Course may be split to assist tamping. 3. Floor slab perimeter insulation with minimum R-value of 0.75m 2 K/W - see table. * Thermal conductivity Light Steel Frame

146 7.09 Raft foundation. To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor/perimeter insulation. 2. Screed must have edge insulation with minimum R-value of 0.75m 2 K/W - see table. Alternatively a timber floor finish with a vapour control layer can be used. 3. Insulating coursing blocks must be used under frame to suit floor levels (minimum of one brick course). * Thermal conductivity Light Steel Frame

147 In-situ suspended ground floor slab. Insulation above slab To achieve R=0.75m 2 K/W (note 2) λ * Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor/perimeter insulation. 2. Vapour control layer under timber floor finish. Alternatively a screed can be used with edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. Alternatively frame may be fixed to split course to suit floor levels. * Thermal conductivity Light Steel Frame

148 7.11 Precast concrete ground floor. To achieve R=0.75m 2 K/W (note 2) λ* Thickness (W/mK) (mm) Continue wall insulation at least 150mm below top of floor/perimeter insulation. 2. Vapour control layer under timber floor finish. Alternatively a screed can be used with edge insulation with minimum R-value of 0.75m 2 K/W (not shown) - see table. 3. Ventilated sub-floor (vents not shown). Alternative arrangements for DPC and DPM may be used. Frame may be fixed to split course to suit floor levels. * Thermal conductivity Light Steel Frame

149 Separating wall Plan view 1. Alternative positions of insulation within separating wall are permissible. Refer to Approved Document B for fire safety requirements relating to separating walls. Refer to Approved Document E for sound insulation requirements relating to separating walls and their associated flanking constructions. Light Steel Frame

150 7.13 Lightweight intermediate floor. 1. Continue wall insulation across floor zone. Separating/compartment floors may require additional layers/components to meet acoustic and fire safety requirements. Balconies may be built so long as the wall insulation layer is not broken. The balcony/supports may be tied back through the insulation so long as any penetrations are sealed. Light Steel Frame

151 8 Robust Details General Arrangements 8

152 Contents Introduction Section 1 Masonry: External Wall Insulation Section 2 Masonry: Cavity Wall Insulation: Full-Fill Section 3 Masonry: Cavity Wall Insulation: Partial-Fill Section 4 Masonry: Internal Wall Insulation Section 5 Timber Frame Section 6 Light Steel Frame Section 7 General Arrangements Section 8 Introduction Air leakage Pitched roof. Ventilated rafter void. Window Pitched roof. Ventilated batten void (warm roof). Window Loft hatch Level threshold. Insulation above slab Level threshold. Insulation below slab Level threshold. Timber floor 8.07 Service penetrations General Arrangements

153 Introduction General Arrangements This section shows details appropriate to all forms of construction covered by Robust Details. For the purposes of illustration details may be shown with one particular form of construction but the principles may be carried across to other types of construction. Although the drawn details all show brick cladding, they are appropriate for a range of other claddings subject to suitable detailing. General Arrangements

154 8.01 Air leakage. Many of the details shown in this document contain measures designed to reduce air leakage. The individual air tightening measures will depend on the form of construction and level of workmanship but the objective is to form a definable, continuous air leakage barrier around the dwelling. Ways of preventing air leakage should then be considered at every penetration of this barrier. Particular care on site should be paid to: Joints between structural components e.g. wall to floors. Joints around components and opening within walls. Services penetrations plumbing, electrical, and ventilation. General Close any vertical ducts at top and bottom (e.g. boxing in to SVPs). Seal any service penetrations. Select the appropriate sealant or gap filler for the size of gap and degree of movement anticipated. Masonry construction Ensure continuous ribbons of adhesive are used to fix to dry lining at perimeters of external walls, openings, and services on external walls as shown (right). The importance of correct sealing of dry lining on dabs needs to be stressed, as this is a key area of air infiltration and can seriously effect the overall ventilation rate. Use joist hangers to support floor joists. Seal under skirting boards where dry lining is used, or on suspended floors. Timber frame Ensure DPCs are turned up behind sole plates and lap with vapour control layers; alternatively seal with mastic or a gasket between the DPC and sole plate. Place bead of mastic on timber floor deck before positioning wall panels (timber ground floors and intermediate floors). Ensure sheet vapour control layers are properly Positions of continuous ribbons of adhesive lapped at junctions, and/or, for dry lining fixed to external masonry walls. Ensure any vapour control plasterboard is jointed in accordance with manufacturer s instructions. Always return vapour control layers into door and window reveals, heads and sills. Cut vapour control layers tight to electrical outlets and seal at piped service penetrations, (with tape or sealant as appropriate). Ensure all breather control membranes overlap each other and are stapled in place. Steel frame All joints between rigid insulation boards should be lapped or sealed with tape approved by insulation manufacturer. Additional items where hybrid construction is used: Ensure sheet vapour control layers are properly lapped at junctions, and/or, Ensure any vapour check plasterboard is jointed in accordance with manufacturer s instructions. Always return vapour control layers into door and window reveals, heads and sills. Cut vapour control layers tight to electrical outlets and seal at piped service penetrations. General Arrangements

155 Roof window. Ventilated rafter void To achieve R=0 34m 2 K/W (note 4) λ* Thickness (W/mK) (mm) Window frame to be level or lower than top of rafter. 2. Pack with mineral wool (or similar). 3. Push insulation into gap between frame and tile batten. 4. Reveals to be insulated with insulation of minimum R-value of 0.34m 2 K/W - see table. Thermal conductivity General Arrangements

156 8.03 Roof window. Ventilated batten void (warm roof). To achieve R=0.34m 2 K/W (note 4) λ* Thickness (W/mK) (mm) Window frame to be level or lower than top of counter batten. 2. Pack with mineral wool (or similar). 3. Push insulation into gap between frame and tile batten. 4. Reveals to be insulated with insulation of minimum R-value of 0.34m 2 K/W - see table. * Thermal conductivity General Arrangements

157 Loft hatch Ensure that loft hatch is fully draught stripped. Counter bearers and boarding should be provided if access to loft is required. Note that U-value through loft hatch must be no worse than 0.35W/m 2 K (poorest acceptable U-value). General Arrangements

158 8.05 Level threshold. Insulation above slab. 1. Continue floor insulation up to back of sill. 2. Optional insulation for casting of slab (not required for thermal bridging purposes). This detail is provided to show the position of insulation. Slab details and positions of DPCs and DPMs may vary according to wall and floor type. General Arrangements

159 Level threshold. Insulation below slab Alternative section To achieve R=0.75m 2 K/W (see notes) λ* Thickness (W/mK) (mm) Timber/plastic/composite - continue floor perimeter insulation with minimum R-value of 0.75m 2 K/W to underside of sill - see table. 2. For other sills continue floor perimeter insulation with minimum R-value of 0.75m 2 K/W to rear of sill (alternative detail) - see table. These details are provided to show the position of insulation. Slab details and positions of DPCs and DPMs may vary according to wall and floor type. * Thermal conductivity General Arrangements