GRP fibreglass roofing across Monmouthshire

Price per m²

£69–£129

Typical life

20–40 years

Manufacturer guarantees

20–25 year material warranties on specified systems

Typical garage roof

£1,650–£3,000

How much does a GRP fibreglass roof cost in Monmouthshire?

Guide prices including VAT at Wales rates. The fixed price comes after a free survey for new and replacement roofs.

Which flat roofs are common in Monmouthshire?

Flat roofs in Monmouthshire sit on terraced streets with flat-roofed rear kitchens and bathrooms, 1930s semis with flat-roofed garages and kitchen extensions and newer estates where the first extension roofs are now being replaced. Wales averages roughly 1,460 mm of rain a year, among the wettest in Britain, so we design for steady run-off: proper falls, clear outlets and upstands well above the finished roof. Approximate 1991–2020 regional averages based on Met Office data.

Building regulations in Wales

Welsh guidance is that most re-roofing needs building control approval, so it's worth checking whenever more than a quarter of a roof is replaced or repaired. Renovated roofs are upgraded to around 0.16 W/m²K where feasible, and new extension roofs are built to 0.13 W/m²K under the Welsh Approved Document L. In Monmouthshire the application goes to Monmouthshire County Council. More on the rules.

How long does a GRP roof last, and is it guaranteed?

A properly laid GRP roof typically lasts 20 to 40 years. The range is wide because so much depends on the laminate being fully wetted out, the deck staying dry and stable, and the topcoat being renewed if it wears.

When GRP fails early, the cause is usually one of these:

• resin laid in damp or cold conditions that never fully cured;
• cracks at board joints or trims where movement was not allowed for;
• a deck that was wet, soft or poorly fixed before laminating;
• a thin or patchy topcoat that has weathered through.

On guarantees, manufacturer material guarantees are available on many specified GRP systems, and some need a registered build-up or an approved installer. Where registration is possible, we do it for you. Every re-roof also comes with our written workmanship guarantee, with the length set out in your quote, and you can ask about insurance-backed options. Read more in our guarantees guide.

Why do GRP roofs crack, and can weather affect the installation?

GRP usually cracks where the structure moves and the laminate cannot, typically along board joints, at the junction with trims, or where a roof meets a wall. Weather during laying is the other big factor, because resin cures by chemical reaction and that reaction is sensitive to temperature and moisture.

How we reduce the risk of cracking:

• boards fixed at close centres so the deck does not flex;
• joints taped and reinforced with an extra strip of mat;
• wall junctions finished with a separate trim or flashing, not laminated hard into the masonry;
• roofs over a certain size divided with movement details where the system calls for them.

And how weather is managed:

• no laminating in rain, on a damp deck, or when dew or frost is likely before the resin sets;
• catalyst levels adjusted for the temperature, so resin neither stays tacky on a cold day nor kicks too fast in summer heat;
• the roof sheeted over if a shower threatens a fresh laminate.

That is why a GRP date can move at short notice. A day's delay costs far less than a laminate that never cures properly.

Which towns in Monmouthshire do we cover?

• Abergavenny
• Chepstow
• Monmouth
• Caldicot

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