These figures are illustrative, not quotes
What affects the cost
Before looking at any numbers, it helps to understand the variables that move the price. These are what a roofer weighs up when pricing the job.
The membrane system
The covering is the biggest choice. Felt is the cheapest but shortest-lived; EPDM rubber and GRP fibreglass cost more but last far longer, so the "cheapest" option is not always the best value over the life of the roof.
Size and detailing
Cost scales with area, but the upstands, outlets, corners and any roof lights are where the skilled work lies. A small roof with lots of detailing can cost more than a larger, simpler one.
Deck condition and insulation
If the timber deck is soft or rotten it must be renewed before the new covering goes on, and adding or upgrading insulation to meet current standards affects the price too.
Correcting the falls
If the old roof ponded because the fall was inadequate, putting that right — often with tapered insulation — is an extra but is essential to stop the new roof failing the same way.
Access
A ground-floor extension roof is easy to reach; a flat roof at height or over a difficult area may need scaffolding or edge protection, which adds to the cost.
Illustrative cost ranges
Illustrative — not a quoteThe ranges below are a starting point for understanding likely costs. Treat them as ballpark figures for setting expectations, not as a price for your job.
Illustrative flat-roof ranges — not quotes. Detailing and deck condition change these significantly.
| Membrane | Illustrative supply & fit (per m²) | Typical lifespan |
|---|---|---|
| Felt (torch-on) | £50 – £90 / m² | 10 – 20 years |
| EPDM rubber | £80 – £130 / m² | 25 – 35 years |
| GRP fibreglass | £90 – £150 / m² | 25 – 30 years |
| New timber deck (add-on) | £25 – £50 / m² | As substrate |
Illustrative totals for a typical single garage or small extension roof — not quotes.
| Scope | Illustrative total range |
|---|---|
| Small extension, EPDM | £1,500 – £3,500 |
| Single garage, felt | £1,000 – £2,500 |
| Add tapered insulation to correct falls | £400 – £1,200 |
What’s usually included
Typically included
- Stripping the old covering and clearing the deck
- The chosen membrane and its detailing accessories
- Forming or correcting upstands, edges and outlets
- Labour for the installation
Often not included
- Renewing a rotten timber deck unless found and quoted
- Correcting inadequate falls unless specified
- Insulation upgrades to meet current standards unless included
- Scaffolding for roofs at height
Get a price for your roof
The only way to know what your job will cost is a quote from a roofer who has seen it. Get a free, no-obligation quote from a trusted local roofer.
