Flat roof replacement cost
A flat roof replacement typically costs £2,900 in the UK, with most jobs between £1,200 and £6,500. That includes VAT at 20%. There is no grant for this work, so the figure above is what you would actually pay.
- Typical range £1,200–£6,500
- Most people pay £2,900
- VAT 20%
- On site 2–5 days
What you would actually pay
Typical 3-bed semi · UK- Typical installed cost Flat roof replacement, supplied and fitted
- £2,400
- VAT at 20% Standard rate
- £500
- Net cost to you
- £2,900
If you borrowed £2,880.00 over 36 months at 0.0%, it would cost £80.00 a month — £2,880.00 in total, of which £0.00 is interest.
Illustration only — not a quote, not an offer of credit, and not financial advice. Rates depend on your circumstances and creditworthiness.
Where the money goes
| Element | Typical range |
|---|---|
| Stripping the old covering Felt comes off quickly; asbestos-containing sheets do not and must be handled separately. | £200 – £600 |
| Decking repairs Soft or rotten boards are common on older felt roofs and are replaced before anything goes on top. | £200 – £1,000 |
| New covering Torch-on felt is cheapest, EPDM rubber mid-range, GRP fibreglass dearest. | £500 – £2,500 |
| Edge trims and outlets Drips, upstands and the outlet itself, which is where most flat roofs fail. | £100 – £600 |
| Insulation Bringing a warm-deck roof up to current standards, where Building Regulations apply. | £0 – £1,200 |
Guide prices. Your actual cost depends on your property, access and specification.
What should be in a quote
If a quote is missing any of these, ask why before you compare it with another.
- Which covering, named by system and manufacturer
- Whether the decking is being replaced or reused
- New outlets and edge trims, not reusing the old
- Whether insulation is included and to what standard
- The falls, and how water will actually reach the outlet
- Guarantee length and whether it is backed by the manufacturer
What moves the price
- Which system you choose
Torch-on felt is the cheapest and lasts perhaps fifteen years. EPDM rubber costs more and lasts twenty-five or more. GRP fibreglass is dearest and gives a seamless finish, but it needs dry weather to install.
- The state of the deck
You only find out once the covering is off. Budget for some board replacement on any roof over twenty years old, and expect the quote to carry a rate for it.
- Building Regulations
Replacing more than half the roof area usually triggers a requirement to insulate to current standards, which adds both material cost and height at the edges.
- The falls
If the existing roof ponds, the falls are wrong and simply re-covering it will not fix that. Correcting them means firring the deck, which is extra.
Common questions
How long does a flat roof last?
Torch-on felt around fifteen years, EPDM rubber twenty-five or more, and GRP fibreglass twenty to thirty. The covering matters less than the detailing at the edges and outlets, which is where most of them fail first.
Do I need Building Regulations approval?
If you are replacing more than half the roof area, yes, and it will usually need insulating to current standards. A like-for-like patch does not.
Why does my flat roof hold water?
Because the falls are too shallow or have sagged. Ponding shortens the life of any covering, and re-covering without correcting the falls just buys you the same problem again in a few years.