Flat Roof Replacement Cost in the UK

Flat roofs are common on UK extensions, garages, porches, and some modern properties. When they start to fail, replacement is often more cost-effective than ongoing repairs. Here's a comprehensive guide to flat roof replacement costs in 2026.

Flat Roof Replacement Costs by Material

Material	Cost Per m²	Lifespan	Best For
3-Layer Felt	£50 – £70	10–20 years	Budget option
EPDM Rubber	£80 – £120	25–50 years	Best all-rounder
GRP Fibreglass	£90 – £130	25–40 years	Seamless, walkable
Single-Ply (PVC/TPO)	£70 – £100	20–30 years	Larger flat roofs
Lead	£120 – £180	50–100+ years	Premium/heritage

Total Cost by Roof Size

Roof Size	Felt	EPDM	GRP
10 m² (porch)	£500 – £700	£800 – £1,200	£900 – £1,300
20 m² (garage)	£1,000 – £1,400	£1,600 – £2,400	£1,800 – £2,600
30 m² (extension)	£1,500 – £2,100	£2,400 – £3,600	£2,700 – £3,900
50 m² (large extension)	£2,500 – £3,500	£4,000 – £6,000	£4,500 – £6,500

EPDM vs GRP: Which Should You Choose?

These are the two most popular modern flat roof materials. Here's how they compare:

EPDM is slightly cheaper and extremely durable. It's a single rubber sheet that's bonded to the roof deck, making it watertight with no joins.
GRP provides a seamless, hard-wearing finish that can be walked on. It's ideal for balconies or roof terraces but costs a bit more.
Both offer excellent lifespans of 25+ years when properly installed.