Commercial roof refurbishment
Refurbish in place · flat and metal roofs · building stays in use
Refurbishment means giving an existing roof a new waterproof life without stripping it back to the deck. On flat roofs that is usually a reinforced liquid membrane over the old covering, at about £40 to £90 per m². On metal roofs it is overcladding with a new insulated roof built over the old, at about £45 to £65 per m².
Both keep the building open and avoid the cost and risk of a strip-out. Both only work if a survey shows the structure and, on flat roofs, the insulation below are sound and dry.
When refurbishment is the right call
The deck is sound
Cores on a flat roof show dry insulation and a firm deck. On a metal roof, the purlins and frame are in good order.
The building cannot close
Live warehouses, schools in term, offices and production lines stay open: nothing is removed above people's heads.
Leaks are widespread but the roof is not wet through
Many small failures across an ageing covering, rather than a saturated roof.
There may be asbestos in the old roof
Overcladding leaves fibre cement sheets sealed in place rather than disturbing them.
Typical refurbishment costs
| Item | Scope | Typical cost |
|---|---|---|
| Liquid membrane over a flat roof | Reinforced polyurethane or PMMA over the cleaned and primed old covering | £40 to £90 per m² |
| Overcladding a metal or fibre cement roof | Spacer system, insulation and new profiled sheets over sound old sheets | £45 to £65 per m² |
| Insulation upgrade on a flat roof | New insulation layer added, extra over | £20 to £40 per m² |
| 1,000 m² flat roof, liquid overlay | Worked from the per m² rate | £40,000 to £90,000 |
| 2,000 m² metal roof, overclad | Worked from the per m² rate | £90,000 to £130,000 |
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.
The three ways to refurbish
Liquid-applied membranes on flat roofs
The old felt, asphalt or single ply is cleaned, loose areas cut out and repaired, a primer goes down and then a liquid membrane is laid, usually with a fleece reinforcement embedded in it. It cures into one seamless sheet that runs up upstands and around awkward details. Reinforced systems from established makers are commonly guaranteed for ten to twenty-five years. See liquid roofing.
Overcladding metal and fibre cement roofs
Brackets are fixed through to the purlins, a new rail system sits on top, insulation fills the gap and new profiled sheets go over. The building gains a new, insulated roof without the old one coming off. It suits industrial units with corroded sheets or asbestos cement roofs. See roof overcladding.
Coatings on sheet and panel roofs
Where sheets are sound but laps and fixings leak and coatings are failing, a coating system can seal the laps and recoat the roof. It is cheaper than overcladding and does less: it will not add insulation. Treating rust at the edges first is essential; see cut edge corrosion.
The insulation question
Under the building regulations in England, renovating more than half of a roof's surface means bringing that roof up to the current insulation standard (a U-value of 0.18 W/m²K for buildings other than dwellings) where that is technically, functionally and economically feasible, judged by a simple payback of under 15 years. A refurbishment specification should say how it deals with this.
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, Fragile surfaces
Prices are typical ranges from published UK contractor price guides and roofing firms' price pages, November 2026.
Get a refurbishment priced by a contractor who overlays and overclads roofs like yours.
Get contractor quotesHow the job runs
A refurbishment runs in phases across the roof, so the building below stays dry and open.
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.
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.
Preparation
Defects repaired, outlets cleared, rust treated or wet areas cut out and replaced so the overlay goes onto a sound base.
Overlay or overclad, section by section
Worked across the roof in bays, each one watertight at the end of the shift.
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.
Refurbishment questions
Is refurbishment cheaper than replacing the roof?
- Usually. A liquid overlay at £40 to £90 per m² compares with £90 to £140 per m² for a single ply strip and replace, before insulation. The bigger saving is often in avoided strip-out, waste and disruption. It only works if the old roof is dry and sound underneath.
How long does a refurbished roof last?
- Reinforced liquid systems are generally rated for 20 to 30 years, with maker guarantees of ten years or more. Overcladding gives the life of a new metal roof, typically 25 to 40 years depending on the coating.
Can you overlay a roof that is already leaking?
- Yes, if the leaks are local and the insulation is dry. Wet areas are cut out and replaced first. If large parts of the roof are wet through, a strip and replace is usually the honest answer.
Do I need building regulations approval for roof refurbishment?
- Re-covering a roof is building work, and renovating more than half of it triggers the energy efficiency requirements. Contractors registered with a competent person scheme can self-certify some roof work; otherwise building control must be notified. Ask who is handling it.
Will the building have to close?
- Rarely. Liquid overlays and overcladding are done from above without removing the old roof, so work below can usually carry on with some areas protected.
Read next
- Liquid roofing and coatings
Overlay systems for flat roofs.
- Roof overcladding
A new metal roof over the old one.
- Commercial roof replacement
When the roof has to come off.
- Commercial roof cost calculator
Compare the routes for your area.
Get a refurbishment 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.
Your request stays with us until you approve the independent commercial roofing contractor we put forward for your building.
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- Nothing goes to them until you say yes.
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