TR-19 – Warm Flat-Roof Detail

This detailed drawing shows a typical warm flat-roof edge junction with a rendered traditional masonry cavity wall.

The drawing illustrates a proprietary waterproofing membrane, rigid insulation above the roof deck, vapour-control layer, structural deck, timber firrings, roof joists, internal ceiling and perimeter edge trim. It demonstrates how the roof insulation and vapour-control layer should connect with the external wall to maintain thermal and airtightness continuity.

The warm-roof build-up shown includes:

• Accredited single-ply membrane or GRP waterproofing.
• Proprietary separation or isolation layer where required.
• Rigid PIR insulation installed above the roof deck.
• Continuous sealed vapour-control layer.
• External-quality plywood or OSB3 roof deck.
• Timber firrings or supporting structure formed to falls.
• Structurally designed roof joists and trimming members.
• Internal plasterboard ceiling finish.

Supporting notes also cover roof falls, perimeter trims, waterproofing upstands, outlets, emergency overflows, thermal breaks, cavity barriers and fire-stopping. The drawing includes the calculated PSI value and temperature factor applicable to the illustrated junction.

The customer receives one downloadable PDF construction drawing, prepared at a scale of 1:10 and formatted for an A3 sheet.

The waterproofing must be installed as a compatible proprietary system by an appropriate specialist contractor. Roof structure, insulation thickness, drainage outlets and condensation control must be confirmed for the project-specific structural design, energy assessment and roofing manufacturer’s requirements.