REF · CHECKLIST · FREE
Flat roof health check — the 12-point home checklist
Twelve things to inspect from the ground (or a Velux) to know whether your flat roof needs a repair, a retrofit, or a full replacement. Written by Sean Brown — owner of Eco Roofers — from the same survey checklist we use on paid jobs.
How to use this checklist
Walk round your flat roof and look at it from two angles: from the ground floor up (looking under the soffit and along the gutter line), and from above if you have a Velux or an upstairs window that overlooks. Tick each item that applies. The scoring system at the bottom tells you what to do.
The 12 signs your flat roof needs attention
What your score means
0 ticks: Your flat roof is in good order. Re-check annually — they age fast in the UK climate.
1–3 ticks: Repair territory. A specific issue is showing but the roof has years left. Book a free survey, get a written quote for the targeted fix. Usually £150–£550.
4–7 ticks: End-of-life approaching. EPDM replacement (often as a warm-roof retrofit per Building Reg L1B) is the best move. The patches will cost more cumulatively than a one-off replacement in the next 2 years.
8+ ticks: Replace now. Continuing to patch is throwing good money after bad. The interior damage from a leak you don’t catch will cost more than the roof. Call Sean on 07929 379 746 for a free same-week survey.
What we look for on a paid survey (that you can’t see)
If you book a free 30-minute survey from us, we look at the things this list can’t catch:
- Insulation moisture content with a calibrated meter through a small core sample — tells us whether the deck is wet or dry under the membrane
- Joist condition from inside via the loft hatch or a removed Velux flashing
- Roof fall slope with a spirit level across the longest run — should be 1:80 minimum per BS 6229
- Existing vapour barrier integrity — visible through the soffit detail in most cases
- Wind uplift fixings on the edge trims — visible only when partially lifted
The most common false alarm
Bubbles on a felt roof in the first 2 years. New felt outgasses and tiny bubbles appear. They flatten on cooling and don’t indicate a fault. If your felt is under 2 years old and the bubbles aren’t lifting the surface or leaking — leave them.
Common questions
How often should a flat roof be inspected?
UK climate: annually for a felt roof, every 2 years for EPDM/GRP. After every named storm. After any work on the roof above (e.g. a chimney repointing) where debris could have damaged the membrane.
Can I patch a flat roof myself?
For a single split under 50 mm: yes, with a self-adhesive felt patch from a builders’ merchant. Anything bigger or anywhere near an edge / flashing: no — you’ll trap moisture under the patch and accelerate the failure. We charge £150–£280 for a proper patch on a domestic flat roof.
Is rainwater under the membrane dangerous?
Long-term, yes — wet timber rots, wet plaster blackens, wet insulation loses its R-value. Short-term it’ll mostly just stain. Don’t panic but don’t ignore it.
What’s the cheapest fix on a tired flat roof?
For a roof under 12 m² with no structural issues: a felt overlay (new felt bonded directly over the old) — £400–£900. Lasts 5–8 years and buys you time. Not our recommended approach but valid if budget is tight.
