EPDM warm-deck flat roof · 2025
Kitchen extension flat roof
A new open-plan kitchen extension needed a flat roof that would never leak over the family’s brand-new island. We built a warm-deck with 120mm insulation, tapered firrings for a clean fall, and a single sheet of EPDM rubber dressed into a powder-coated aluminium trim.
Job sheet
- Location
- Dore, S17
- Scope
- Warm-deck build-up & membrane
- Materials
- Firestone RubberCover EPDM
- Duration
- 3 days
- Deck area
- 46 m²
- Insulation
- 120 mm
- Guarantee
- 25 yr
Before
Bare timber deck and a builder’s temporary felt covering, ponding water after every shower of rain.
After
A seamless black EPDM warm-deck with crisp aluminium edge trim and a concealed outlet, guaranteed twenty-five years.
What we found once the scaffold was up
The builder had left the deck dead flat, so rainwater was standing exactly where the rooflight was due to go. Left alone it would have been ponding over a brand-new kitchen inside a winter.
How it was built back
Tapered firrings set a 1:80 fall to a single concealed outlet, then 120mm of PIR above the deck so the insulation line is unbroken. That is a warm deck: no cold void, no interstitial condensation quietly rotting the joists, which is what killed most of the flat roofs we get called to. One uncut sheet of EPDM over the top. No seams means nothing to split in twenty-five years.