Commercial roof replacement
Strip and replace · new insulation · new guarantee
A full replacement strips the roof back to the deck or frame and builds a new one, usually with new insulation to meet current standards. On a flat roof that typically costs £80 to £180 per m² depending on the system, and a published example puts a 200 m² three-layer felt roof at £16,000 to £24,000.
It is the most disruptive route and the one with the longest life ahead of it. It is the right answer when the insulation is wet, the deck is failing or the old roof is beyond refurbishment.
Signs the roof needs replacing
Wet insulation across large areas
Cores and moisture surveys find water spread through the build-up. Overlaying would trap it.
A soft or damaged deck
Timber decks rot, metal decks corrode and woodwool slabs lose strength once wet. The deck has to be repaired or replaced first.
Past its expected life with repeated leaks
An old felt roof that has been patched for years, or a metal roof perforated across many sheets.
Asbestos sheets you want rid of
Removing fibre cement sheets rather than overcladding them, ahead of a sale, a change of use or a solar installation.
Typical replacement costs
| Item | Scope | Typical cost |
|---|---|---|
| Built-up felt, strip and replace | Three-layer modified bitumen, torch-on or cold-applied | £80 to £120 per m² |
| Single ply, strip and replace | PVC, TPO or EPDM membrane | £90 to £140 per m² |
| New insulation | Extra over, to meet the energy rules | £20 to £40 per m² |
| Timber deck replacement | Extra over where the deck has rotted | £25 to £50 per m² |
| Metal roof, strip and re-roof | Profiled sheets on an existing frame | £65 to £85 per m² |
| Asbestos sheet removal and disposal | Trained operatives, hazardous waste | £25 to £90 per m² |
Budget figures read from national price guides and roofers' own published rates in November 2026, shown before VAT. Use them to plan; the contractor's written price is what counts. Work out a budget for your roof.
What a replacement involves
Strip-out and the deck
The old covering and insulation come off in sections, so only a small area is open at any time. The deck is inspected: soft timber boards, corroded metal deck and damaged woodwool slabs are replaced. On older buildings, the strip-out is where asbestos in old bitumen, felt or sheets may turn up, which is why a refurbishment and demolition asbestos survey should be done before work starts.
Insulation and the energy rules
Replacing a roof counts as renovating it. In England, the roof must then meet a U-value of 0.18 W/m²K for buildings other than dwellings where that is technically, functionally and economically feasible (a simple payback of under 15 years). Raising the insulation thickness can mean raising upstands, outlets and rooflight kerbs, all of which should be in the price.
Choosing the new system
For flat roofs, single ply is the most common choice on large commercial roofs and built-up felt remains popular where foot traffic is heavy. For metal roofs, a new insulated sheet or composite panel roof goes onto the existing frame. The cost calculator compares the routes for your area.
Programme
Work runs in phases with each section made watertight at the end of every shift. A school roof is often planned for the summer holiday; a warehouse roof is phased around racking and production. Weather sets the pace for most flat roof systems.
Where our information comes from
- GOV.UK, Approved Document L: conservation of fuel and power (2021 edition)
- NFRC, BS 6229:2025 update: key points for members (December 2025)
- HSE, Non-licensed work with asbestos (updated February 2024)
- HSE, Fragile surfaces
Prices are typical ranges from published UK contractor price guides and roofing firms' price pages, November 2026.
Planning a replacement? Get it priced by a contractor who replaces roofs of that size and type.
Get contractor quotesHow the job runs
A typical replacement on an occupied building, in order.
Survey
A contractor walks the roof where it is safe to, or flies a drone where it is not, takes cores on flat roofs and photographs every defect. You get a written report with a recommendation.
Asbestos and structure checks
An asbestos survey where the building pre-dates 2000, and a structural check if the new roof is heavier or adds solar panels.
Specification and price
A written scope naming the system, the details at edges, outlets and rooflights, the guarantee and the programme, with a fixed price excluding VAT.
Phased strip and replace
Old roof off and new roof on in bays, each made watertight before the shift ends.
Handover
A final inspection, photographs, the guarantee certificate, building control completion where it applies, and a note of when the next maintenance visit is due.
Replacement questions
How much does a commercial roof replacement cost per m²?
- Published flat roof replacement prices run £80 to £180 per m², depending on the system and access. Single ply is typically £90 to £140 per m² and three-layer felt £80 to £120 per m². Add £20 to £40 per m² for new insulation and £25 to £50 per m² where the deck needs replacing. Prices exclude VAT.
How much is a 1,000 m² flat roof?
- Worked from the published rates, £90,000 to £140,000 for single ply strip and replace, or about £110,000 to £180,000 with new insulation. Access, height, the number of rooflights and plant, and the region all move the figure.
Do I need planning permission to replace a commercial roof?
- Not usually for a like-for-like covering. Changing the roof's shape or height, a listed building, or a conservation area may need consent. Building regulations do apply: the work must be notified and meet the energy rules.
How long does a roof replacement take?
- A few days for a small roof, several weeks for a large warehouse or school roof, depending on access, weather and how much of the building must stay in use. The contractor's programme should show it phase by phase.
Is VAT charged on commercial roof replacement?
- Yes, at the standard rate in most cases. Prices on this site exclude VAT. Charities and some residential buildings can be treated differently; ask your accountant.
Read next
- Single ply roofing
The most common new commercial flat roof.
- Commercial flat roofing
Felt, single ply and liquid compared.
- Commercial roof refurbishment
If the roof can be kept.
- Commercial roof cost calculator
A budget for your area.
Get a roof replacement priced
Three short steps. The postcode, what the roof is and what it is doing is enough to start. A contractor confirms the detail on a survey.
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- Nothing goes to them until you say yes.
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