Garage Roof Cost Calculator
The cheapest garage roof is rarely the best value. This prices felt, EPDM, GRP and a pitched conversion side by side, with their working lives.
Open the calculator →Price a garage roof in 30 seconds
4 steps. Covers covering type, roof size, deck condition and region.
How this calculator works
Costs are scaled from a standard single garage of 18m², which is what the published ranges assume. The breakdown shows the expected life of whichever covering you pick, because that is the comparison worth making: felt at £1,050 for 15–20 years is roughly £60 a year, EPDM at £1,800 for 20–30 years is closer to £70 — but the EPDM will not need patching in between.
The deck is the unknown. Under an old felt roof it is frequently soft in places, and a new covering laid over a failing deck fails early. If you can walk on the roof and feel any give, assume partial replacement at minimum.
Garage roof costs by covering (2026)
| Covering | Typical 2026 cost | Notes |
|---|---|---|
| Felt (torch-on, 3-layer) | £700–£1,500 | 15–20 years |
| EPDM rubber membrane | £1,200–£2,500 | 20–30 years, few seams |
| GRP fibreglass | £1,500–£3,000 | 20–30 years, seamless |
| Pitched / tiled conversion | £2,500–£6,000 | 40–60 years |
| Deck replacement (partial) | £250–£500 | Common on old felt |
| Deck replacement (full) | £600–£1,000 | Soft or rotten |
Ranges match our garage roof cost guide and assume a single garage of about 18m².
Garage roof calculator FAQs
EPDM for most garages. It goes down as a single sheet so there are few seams to fail, it lasts 20–30 years, and it is not weather-critical to install. GRP is comparable but needs dry, warmer conditions to cure properly. Felt is cheapest today and usually the most expensive across twenty years.
Often, on an old felt roof. Water gets through failed seams and sits in the deck. If it feels soft or springy underfoot, or you can see staining inside the garage, budget for at least partial replacement — a new covering over a rotten deck will fail early.
If the garage is attached or highly visible, frequently yes. It costs two to three times a flat covering but lasts 40–60 years, looks considerably better, and removes flat-roof maintenance entirely. Check permitted development first — a pitched roof adds height.
It can, and some installers offer it, but it is a false economy. You trap any moisture in the old layer, you cannot inspect the deck, and the guarantee is usually weaker. Strip it.
Related cost guides
- Garage roof cost guide — full 2026 pricing
- Flat roof calculator — for house flat roofs
- EPDM cost guide — the most common choice
- Garage conversion calculator — if you are converting the space
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