Flat Roofs

Not actually flat — and better than their reputation.

A flat roof isn't flat — it's built with a deliberate slight slope ("falls") to move water to an outlet. That distinction is the whole subject: a flat roof with good falls and sound edges is a reliable covering; one that ponds is on the clock regardless of what it's made from.

Where a pitched roof sheds water by overlap, a flat roof is a continuous waterproof skin — which means any single defect matters more. The three modern skins are torch-on felt (economical, proven), EPDM rubber (seamless single sheet, excellent on simple shapes) and GRP fibreglass (rigid, walkable, suits complex shapes). The bad reputation belongs to the cheap mineral felt of decades past, laid flat-flat with no falls — a different product from what's installed today.

You'll find flat roofs on garages, extensions, dormers, porches and bay tops — the full detail on each system lives in our flat roofing hub.

Benefits

Why choose Flat Roofs

Economical to build and to replace
Modern systems: 25+ year working lives
Simple, quick inspection — faults are visible
Usable space potential (balconies, terraces with GRP)
Small areas mean replacement costs stay contained

Features

What's included

Felt, EPDM and GRP systems compared honestly
Falls and drainage assessment
Edge, trim and upstand detailing
Warm-deck and cold-deck build-ups
Rooflight and outlet integration

Typical lifespan

15–30 years by system

Repair options

Repair or replace

Flat roof triage is refreshingly visual: a local split, lifted joint or failed trim on an otherwise sound covering is a repair; blistering, crazing or ponding across the area is the covering finished, and patching it is a subscription. Because the areas are small, replacement quotes are worth getting even when a repair is viable — the gap is often less than expected, and replacement restarts a 25-year clock.

Common questions

Frequently asked

Why did old flat roofs leak so much? +

Cheap mineral felt, laid dead flat, over uninsulated decks that moved and condensated — every part of that sentence has since been fixed. Modern membranes are elastic and UV-stable, falls are designed in, and warm-deck construction keeps the structure stable and dry. The reputation is thirty years out of date.

How long will my flat roof last? +

By system: basic felt 10–15 years, good torch-on systems 15–20, EPDM and GRP 25+. Then subtract for standing water and bad edges — ponding is the great lifespan thief. If you don't know the age of yours, cracking, blistering and bare patches are the visible countdown.

Can a flat roof become a pitched roof? +

Sometimes, and on the right building it's worth considering — a shallow pitched conversion over a troublesome flat roof swaps a 20-year covering for a 50-year one. It's structural work with planning implications, so it suits garages and extensions being improved anyway rather than quick fixes.