TB/15 – Eaves Detail: Pitched Warm Roof

This warm roof eaves detail illustrates the junction between an insulated masonry cavity wall and a pitched roof with rigid insulation fitted between and beneath the rafters or truss top chords.

It is intended for architectural designers, building professionals, contractors, developers and self-builders coordinating roof insulation, ventilation and airtightness. For a plain-English introduction, see our related warm-roof guide; Approved Document L provides the official energy-efficiency guidance.

The detail shows:

• External brickwork and Celcon Solar aircrete block inner leaf
• Partial-fill cavity-wall insulation and clear residual cavity
• Timber wall plate with holding-down straps
• C24 rafters or proprietary roof trusses
• Rigid pitched-roof insulation between the roof members
• Continuous insulated plasterboard or insulation beneath the rafters
• Continuity between roof and cavity-wall insulation
• Purpose-made insulation infill above the wall plate
• Breathable roofing membrane
• Counter-battened ventilation cavity
• Insulated cavity closer or fire-resisting cavity barrier
• Low- and high-level roof ventilation where required
• Vapour-control and airtightness layer
• Sealing of the roof membrane to the wall airtightness layer
• SAP junction reference E11
• Calculated psi value of 0.042 W/m·K

The accompanying specification notes cover roof structure, insulation installation, thermal continuity, ventilation, condensation control, cavity closure, vapour control and airtightness.

What This Warm Roof Eaves Detail Includes

• One downloadable PDF construction drawing
• A3 landscape sheet
• Drawn at 1:10 scale when printed at 100% on A3 paper
• Drawing reference: TB/15
• Detail title: Eaves Detail – Warm Roof

Important Information

This is a standard construction detail intended to provide general design guidance. Rafter or truss sizes, spacing, bracing, bearings and connections must be confirmed by a structural engineer or specialist roof-truss manufacturer.

Insulation thickness, ventilation and vapour-control requirements must be based on the project’s approved U-value calculation, SAP assessment, roofing-underlay certification and condensation-risk assessment. Roof ventilation should only be omitted where supported by the certified roofing system and project-specific assessment.

The stated psi value applies only where the illustrated construction, materials and geometry are followed.

The drawing does not include structural calculations, a truss layout, U-value calculation, condensation-risk analysis, SAP assessment or Building Regulations approval.

The PDF is supplied for use by the purchaser on their own projects. It may not be resold, redistributed or reproduced for commercial resale without written permission.