GRP fibreglass roofing across Hertfordshire

Price per m²

£79–£147

Typical life

20–40 years

Manufacturer guarantees

20–25 year material warranties on specified systems

Typical garage roof

£1,850–£3,400

How much does a GRP fibreglass roof cost in Hertfordshire?

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

Which flat roofs are common in Hertfordshire?

Flat roofs in Hertfordshire sit on 1960s and 1970s link-detached houses with flat-roofed garages and porches, lock-up garage blocks on estates and newer estates where the first extension roofs are now being replaced. The East of England is the driest part of Britain, with parts of the Anglian region around 630 mm a year, so summer heat and UV, not rainfall, do most of the ageing on a felt roof. Approximate 1991–2020 regional averages based on Met Office data.

Building regulations in England

Replacing more than half of a roof over a heated room usually counts as renovating a thermal element, so it is insulated to current standards and notified to building control. Renovated roofs over heated rooms are insulated to around 0.16 W/m²K where that's feasible, and new extension roofs are built to 0.15 W/m²K. In Hertfordshire the application goes to Watford Borough Council, Dacorum Borough Council, Stevenage Borough Council and 7 other councils. 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 Hertfordshire do we cover?

• Watford
• Hemel Hempstead
• Stevenage
• St Albans
• Welwyn Garden City
• Cheshunt
• Hatfield
• Bishop's Stortford
• Borehamwood
• Hitchin
• Hoddesdon
• Letchworth Garden City
• Harpenden
• Bushey
• Hertford
• Rickmansworth
• Potters Bar
• Berkhamsted
• Ware
• Royston

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