Service
Flat Roof Cost per m² (2026)
Straight per-m² prices for a new flat roof in 2026: felt from £75/m², GRP fibreglass £110/m², EPDM rubber £95/m² — all installed, all including new deck if needed and edge trims. Minimum job £1,400.
- Felt (3-layer torch-on): £75–£95/m²
- GRP fibreglass: £100–£130/m²
- EPDM rubber: £90–£115/m²
- New 18mm OSB deck: +£22/m²
- Edge trims, drips & upstands included
- Minimum job £1,400 (mobilisation + waste)
What the per-m² number actually includes
Our quoted rate covers strip-off of the old covering, disposal, new deck if needed (usually needed on anything over 15 years old), the primary membrane, edge trim, upstand detail to abutting walls and a written 15–25 year guarantee. It excludes access equipment above 3m, structural repairs to joists, and rooflight replacement.
Which membrane suits which roof
Small porches and bay canopies — felt or EPDM. Extensions with foot traffic (occasional access) — GRP. Big warm-roof extensions with insulation upgrade — EPDM (single sheet, no seams up to 15m). Anything with a rooflight cluster — GRP moulds around detail better.
- ▸Porch (2–4m²) — felt or EPDM, £600–£1,400
- ▸Bay canopy (2–3m²) — GRP or lead, £550–£1,200
- ▸Small extension (10–15m²) — GRP or EPDM, £1,500–£2,400
- ▸Large extension (25–40m²) — EPDM, £2,800–£4,600
Why cheap quotes come back to bite
A £45/m² 'bargain' felt roof usually means single-layer felt on the existing damp deck, no edge trims, and battens instead of new drip. It lasts 3–5 years. Doing it once properly at £85/m² lasts 20+ and you don't repaint the extension ceiling every winter.
FAQs
Is Building Regs approval needed?+
For a like-for-like replacement, no. For a warm-roof upgrade (adding insulation above the deck) or a change from cold to warm roof construction, yes — Part L applies.
Can I have a walk-on flat roof?+
Yes — GRP with a walk-on topcoat, or EPDM with pavers on pedestals over a protection board. Adds £30–£60/m².
How long does the job take?+
20m² extension: 2 days. 40m²: 3–4 days. Weather-dependent — EPDM can't go down in heavy rain, GRP needs 2 dry days for the resin to cure.
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