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What changes the price of a flat roof replacement?
The Federation of Master Builders flat roof guide of 7 November 2025, updated March 2026, says the average cost of a flat roof replacement is £8,000 [S11]. Prices vary by the job and the location and are not a Cheshire price, and QuoteZila does not set prices.
Last reviewed:Replacement is not a patch
A flat roof replacement means the covering comes off and a new one goes on, over whatever structure is there. A local repair that leaves most of the sheet in place is a different instruction. The Planning Portal's re-roofing note says that after a period of time the roof on existing buildings will need to be replaced, and that in most situations this work will need building regulations approval [S1]. It also says some repairs to flat roofs will not require an application for approval [S1]. Your post should say which of those you think you want, and that you may be wrong.
The first houses in mind are in Crewe, Nantwich and Sandbach. Anyone in the UK can post. The Federation of Master Builders flat roof replacement guide of 7 November 2025, updated March 2026, says the average cost of a flat roof replacement is £8,000 [S11]. Its size table, from member firm Aspect, lists £2,800 to £3,600 for 20 square metres, £4,200 to £5,400 for 30 square metres, £7,000 to £9,000 for 50 square metres, and £9,800 to £12,600 for 70 square metres [S11]. Those bands are not added up into a new total. It is not a Cheshire price, and it is not the price of a pitched roof. Prices vary by the job and the location, and QuoteZila does not set prices.
Insulation is a separate decision from the sheet
If the roof with integral insulation is to be replaced, the Planning Portal says you may be required to upgrade this thermal element and reduce the heat that was originally lost [S1]. That sentence is why two "new felt" quotes can be different jobs. One replaces the sheet. The other rebuilds the warm layer. Ask which one is priced.
A new roof, in the Planning Portal's new-roof note, has to resist weather, resist the spread of fire from one property to another, support loads, provide resistance to heat loss, be ventilated to protect from condensation in most cases, and have adequate drainage [S2]. It says a flat roof usually consists of felting with a slight fall so rainwater can drain off [S2]. Ventilation is not required to a warm roof, where the insulation is above the joists or rafters; otherwise it is a cold roof and air should be able to travel through [S2]. Ask the roofer which of those two layouts they are pricing. This guide does not tell you which you need.
When the limits on a re-cover are crossed
The Planning Portal's page on work to an existing roof says repairs or a re-cover of a pitched or flat roof do not normally need a building control application if less than 25 per cent of the building envelope is affected and less than 50 per cent of the roof is affected [S3]. Approval is needed if you exceed those limits, if you alter the structure, if the new covering's performance in a fire is significantly different, or if a new covering material increases the weight by 15 per cent or more [S3].
A full replacement of one flat roof on a house is often the whole of that roof, which is a question to put to building control rather than a conclusion this page will draw for you. GOV.UK lists replacing roof coverings on pitched and flat roofs among works that can need building regulations approval, and says that approval is different from planning permission [S4]. You might need both [S4]. You do not arrange the approval yourself if you use someone on a competent person scheme [S4].
NFRC says its competent person scheme in England and Wales applies where more than 50 per cent of the roof area is being replaced, and that membership is voluntary [S5].
Planning permission is the other door. The Planning Portal says work to the roof of a house, such as re-roofing, that does not materially affect its external appearance will usually not require planning permission [S6]. If the new covering changes the look, or permitted development rights have been removed, ask the local planning authority [S6]. The allowances it describes are for houses, not for a building containing a flat [S6].
GOV.UK: find your local council for building control. QuoteZila is not affiliated with this organisation.
Edges, weight, and staying off the sheet
HSE says falls from flat roof edges can be prevented by a secure double guardrail and toeboard around the edge [S7]. It says all roofs should be treated as fragile until a competent person has confirmed they are not, and that you should not rely on any sheeted roof, whatever the material, to bear a person's weight [S7]. Felt is a sheet. This guide does not tell you to walk out and measure.
The Planning Portal lists felt among the materials a roof has to carry, with tiles, battens and insulation [S8]. If the new build-up is heavier, that is the 15 per cent question on the existing-roof page, and it is the roofer's to calculate [S3]. Do not invent the percentage yourself.
HSE: work at height. QuoteZila is not affiliated with this organisation.
The lines that make two quotes the same job
Citizens Advice says some traders charge for quotes, so ask first, and to get written quotes from at least 3 traders [S9]. A quote is a fixed price and an estimate is a rough guess [S9]. The trader cannot charge more unless you agree extra work or there was a genuine mistake in the written figure [S9]. If a deposit cannot be avoided, do not agree to more than 25%, and get a receipt [S9]. NFRC says refurbishment estimates can change once the covering is off and the sub-structure is seen, and it recommends an insurance-backed guarantee on refurbishment [S5].
A business registers for VAT when taxable turnover for the last 12 months goes over £90,000, or is expected to in the next 30 days [S10].
| Line | What matching looks like |
|---|---|
| Area | The same flat roof, not the porch plus the main house unless you said both |
| Covering | Material named, not "new roof" |
| Insulation | In the price, or explicitly left as it is [S1] |
| Warm or cold | Which layout, if they are changing it [S2] |
| Drainage | Where water leaves, and the fall [S2] |
| Edge protection | Guardrail arrangement in the access line [S7] |
| Decayed boards | Stop and agree before they are replaced [S5] |
| VAT | Included or extra, beside £90,000 [S10] |
Outlets, upstands, and what the roof must not become
A flat roof fails quietly when the outlet blocks and the fall sends water to a corner with nowhere to go. Ask the quote to name the outlet: a chute into a gutter, a hopper, or an internal pipe. Ask who clears it, and whether that pipe is the roofer's or a plumber's. A new covering that still ponds in the same corner has not answered the Planning Portal's point about a slight fall [S2].
Upstands are the turned-up edges where the flat roof meets a wall. If those edges are short, rain driven against the wall can get behind the sheet. Ask the roofer to say they will remake the upstands, and to name the height in their own words. This guide does not invent a minimum.
People sometimes want to walk on a flat roof, or to put a deck on it. HSE's warning about sheeted roofs is the reason this guide will not treat that as a casual extra [S7]. If the roof is to be a terrace, say so at the start, because the structure, the guarding and the approval are a different design from a covering nobody stands on. Do not add decking in the same sentence as a felt replacement and expect one price to cover both.
Put the postcode and which part of the house the flat roof sits on, kitchen or garage or main house, in the first line of the post. Kerbs around roof lights need the same honesty. A lantern that stays must be weathertight at its own perimeter. Say whether the lantern is in the price. If it is old and the roofer will not warranty the junction, the quote should say the lantern is excluded.
Jobs you might post
These are examples, not taken from real job posts.
- Flat felt roof over a kitchen extension, ponding after rain. Photos from a bedroom window. Ask for a replacement price that states whether insulation is upgraded.
- Garage flat roof, covering split, no room under it used as living space. Ask if they still treat it as a thermal element.
- Flat roof that also has a lantern. Say the lantern stays unless they tell you it cannot. Ask for edge protection in the quote.
Anyone in the UK can post or register. QuoteZila is a new, early-stage project, so how many roofers reply depends on who has joined near you [QZ5]. Up to five matched local businesses can quote [QZ2]. QuoteZila is free for customers and local businesses [QZ1].
What to do with a much smaller total
Citizens Advice says a price a lot lower than the others may mean the work is not the same, or the skills are not [S9]. Check the insulation line and the access line before you decide the smaller total is the one to accept. Pay by card, in stages [S9]. Check insurance yourself [S9].
Flat-roof edges are covered by HSE roof work. Whether approval is needed is on GOV.UK building regulations approval.
This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.
Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.
Posting a job is not open yet
Roofers and builders are the trade pages. Scaffolders if access is separate. A leak that might only be a local repair is the roof repair cost guide. All services.
Questions about flat roof replacement
How much does it cost to replace a flat roof?
The Federation of Master Builders flat roof guide of 7 November 2025, updated March 2026, says the average cost of a flat roof replacement is £8,000. The same page gives size bands from member firm Aspect, including £2,800 to £3,600 for 20 square metres and £7,000 to £9,000 for 50 square metres. It is not a Cheshire price. Prices vary by the job and the location, and QuoteZila does not set prices. A felt repair is a different job from a full replacement.
Does a flat roof have to fall?
The Planning Portal, writing about a new roof, says a flat roof usually consists of felting with a slight fall so rainwater can drain off. Ask the roofer to say how water leaves your roof, and where it goes when it reaches the edge. A covering that holds water is not the same design as one with a fall.
Will replacement need building regulations approval?
The Planning Portal's re-roofing page says that after a time the roof on an existing building will need to be replaced, and that in most situations this work will need building regulations approval. It also says some repairs to flat roofs will not require an application. If the roof with integral insulation is to be replaced, you may be required to upgrade that thermal element.
Is planning permission the same thing?
No. The Planning Portal says work to the roof of a house, for example re-roofing, that does not materially affect its external appearance will usually not require planning permission. Building regulations are a separate question. GOV.UK says you might need both.
What access should be in the price?
HSE says falls from flat roof edges can be prevented by a secure double guardrail and toeboard. It also says all roofs should be treated as fragile until a competent person has confirmed they are not, and not to rely on any sheeted roof to bear a person's weight. This page does not tell you to walk the roof.
Does QuoteZila check roofers?
No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.
Part of Cost guides. All services
Related trades
Cost guides
Related pages
- Gutter Cleaning: What a Quote Should List. A gutter cleaning quote in Cheshire should name each elevation, the downpipes and the access. A clean and a roof repair are different jobs.
- Gutter Repair in Cheshire: What to Ask. What to ask about gutter repair in Cheshire before anyone leaves the ground. This guide prints no pound figure and it gives no ladder method.
Sources
- QZ1: QuoteZila product fact. QuoteZila pricing line.
- QZ2: QuoteZila product fact. QuoteZila FAQ.
- QZ5: QuoteZila product fact. QuoteZila home callout.
- S1: Building regulations: Re-roofing, Planning Portal. Accessed 2026-10-28. https://www.planningportal.co.uk/permission/common-projects/roof/building-regulations-re-roofing
- S2: Building Regulations: New Roofs, Planning Portal. Accessed 2026-10-28. https://www.planningportal.co.uk/permission/common-projects/roof/building-regulations-new-roofs
- S3: Building Regulations: Work to an existing roof, Planning Portal. Accessed 2026-10-28. https://www.planningportal.co.uk/permission/common-projects/roof/building-regulations-work-to-an-existing-roof/
- S4: Building regulations approval, GOV.UK. Accessed 2026-10-28. https://www.gov.uk/building-regulations-approval
- S5: Choosing a roofing contractor: homeowners, National Federation of Roofing Contractors. Accessed 2026-10-28. https://www.nfrc.co.uk/find-a-member/choosing-a-roofing-contractor/homeowners.html
- S6: Roof - Planning Permission, Planning Portal. Accessed 2026-10-28. https://www.planningportal.co.uk/permission/common-projects/roof/roof-planning-permission
- S7: Roof work, Health and Safety Executive. Accessed 2026-10-28. https://www.hse.gov.uk/construction/safetytopics/roofwork.htm
- S8: New Roofs - Weight (Loading), Planning Portal. Accessed 2026-10-28. https://www.planningportal.co.uk/permission/common-projects/roof/building-regulations-new-roofs-weight-loading
- S9: Before you get work done on your home, Citizens Advice. Accessed 2026-10-28. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/
- S10: When to register for VAT, GOV.UK. Accessed 2026-10-28. https://www.gov.uk/register-for-vat
- S11: Flat roof replacement cost guide for UK homeowners, Federation of Master Builders. Accessed 2026-10-30. https://www.fmb.org.uk/resource/flat-roof-replacement-cost-guide-for-uk-homeowners.html