Liquid roofing and roof coatings
Liquid-applied membranes · roof coatings · overlay without strip-out
A liquid-applied membrane is brushed, rolled or sprayed onto a prepared roof and cures into a seamless waterproof layer. Reinforced systems laid over an existing flat roof typically cost £40 to £90 per m², with service lives of 20 to 30 years for polyurethane and PMMA systems.
The appeal for commercial owners is that the old roof stays where it is: no strip-out, no open roof, little disruption below.
When liquid roofing fits
An ageing roof that is still dry underneath
Cores show sound insulation and deck; the covering itself is tired.
Lots of details
Pipes, plant bases, ducts and odd shapes are coated around rather than cut and welded.
Occupied buildings
Schools, care homes and offices stay open; cold-applied systems need no flame on the roof.
Metal roofs with leaking laps
Coating systems seal laps and fixings once rust is treated. They do not add insulation.
Typical costs
| Item | Scope | Typical cost |
|---|---|---|
| Reinforced liquid membrane, flat roof overlay | Clean, repair, prime, membrane with fleece | £40 to £90 per m² |
| 500 m² flat roof overlay | Worked from the per m² rate | £20,000 to £45,000 |
| 1,500 m² flat roof overlay | Worked from the per m² rate | £60,000 to £135,000 |
| Metal roof coating system | Lap and fixing treatment plus full coat | Per job |
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.
Types of liquid system
Polyurethane
Single or two-part systems, usually laid with a polyester fleece embedded in the first coat. Flexible and widely used on felt and asphalt overlays.
PMMA
Fast-curing resin systems that cure in an hour or so even in cool weather, used where a roof can only be open briefly or where details are complex. Typically at the upper end of the price range.
Coatings for metal and fibre cement
Thinner coating systems for sheet roofs, applied after laps and cut edges are treated. They restore weathering and colour but do not make a structurally failing roof sound.
What decides success
Preparation. The surface must be clean, dry and sound, blisters cut out, wet insulation replaced, and the system applied to the maker's specified thickness. A liquid membrane over a wet roof traps the water and fails early. A trusted installer measures and records the wet film thickness as they go.
Where our information comes from
- NFRC, BS 6229:2025 update: key points for members (December 2025)
- GOV.UK, Approved Document L: conservation of fuel and power (2021 edition)
- HSE, Fragile surfaces
Prices are typical ranges from published UK contractor price guides and roofing firms' price pages, November 2026.
Want to keep the old roof and overlay it? Get a liquid roofing contractor near you to price it.
Get contractor quotesHow the job runs
A liquid overlay, start to finish.
Survey with cores
Proves the existing roof and insulation are dry and sound enough to go over.
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.
Repair and prime
Wet areas and blisters cut out, the surface cleaned and primed.
Apply the membrane
Base coat, fleece, top coat, details first, then the field of the roof.
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.
Liquid roofing questions
How much does liquid roofing cost per m²?
- Published fitted prices for liquid systems run £40 to £90 per m², excluding VAT, for an overlay on an existing roof. PMMA and heavily detailed roofs sit at the top of the range.
How long does a liquid roof last?
- Reinforced polyurethane and PMMA systems are generally rated for 20 to 30 years. Thin unreinforced coatings last far less. Guarantees from established makers are commonly 10 to 25 years.
Can liquid roofing go over felt?
- Yes, that is its most common use, provided the felt is well adhered and the insulation below is dry. Loose and blistered areas are cut out first.
Is liquid roofing as good as single ply?
- For an overlay, often the better choice because nothing is stripped. For a new roof on a large open area, single ply is usually quicker and cheaper per square metre. Both are long-lived when properly installed.
Does a roof coating stop a metal roof leaking?
- It can seal leaking laps and fixings once rust is treated. It will not fix perforated sheets, and it adds no insulation. A badly corroded roof needs overcladding or replacement.
Read next
- Commercial roof refurbishment
Overlay, overclad or coat.
- Commercial flat roofing
All flat systems compared.
- Cut edge corrosion treatment
Before any coating on metal.
- Commercial roof cost calculator
Overlay against replace.
Get liquid roofing 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.
Received. Here is what happens next.
- We look for an independent commercial roofing contractor who covers your area and takes on roofs like yours, then email or phone you with their name.
- Nothing goes to them until you say yes.
- If you agree, they arrange a survey and send a written price. No newsletters and no sales calls from us.