A roof-gutter-insulation detail drawing is an enlarged construction drawing at scale 1:5 or 1:10 that shows exactly how the roof plane, gutter and thermal insulation come together at the eaves. At this point, water drainage, insulation, vapour control and structural support all converge — and precisely here many execution errors and thermal bridges arise.
What does the detail drawing show?
A good detail drawing depicts all layers and their connection:
- Roof sheathing or panel connecting to the wall plate
- Insulation layer (PIR, mineral wool or EPS) continued into the gutter zone
- Vapour barrier on the warm side, airtight to the inner skin
- Underlay or breather membrane discharging into the gutter
- Battens and counter-battens above the membrane
- Gutter (eaves gutter, parapet gutter or box gutter) with fall and lead or EPDM connection
- Fascia board with ventilation strip or bird comb
Key considerations
- Avoid thermal bridges — insulation must continue beyond the wall plate, so no heat leaks form
- Ventilation — for a cold roof, a vent gap between insulation and sheathing is needed
- Watertightness — membranes and lead must be laid so rainwater always ends in the gutter
- Airtightness — vapour barrier and membranes are taped to masonry or timber frame
- Fall of the gutter — minimum 1 cm per metre toward the downpipe
Application
Detail drawings are made by the architect or building draughtsman and are a mandatory part of the building permit file for new build and major renovation. During execution they serve as a guideline for carpenter, roofer and insulation installer. For retrofit insulation of an existing roof, an adapted detail drawing is crucial to prevent moisture and mould problems.
Related terms
- Gutter
- Insulation
- Thermal bridge
- Eaves
- Wall plate
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