GRP Fibreglass RoofingSeamless, Walk-On, Guaranteed— Across the Wirral
A single, seamless, walk-on membrane laminated in place — no joints to fail, no seams to lift, a proper 25-year flat-roof solution for extensions, dormers, balconies and porches.
GRP Roofing — what, who, when & why
What it is
In-situ laminated glass-reinforced polyester (GRP) roofing — a wet lay-up of catalysed resin and glass matting over an 18mm OSB3 deck, finished with a coloured topcoat and pre-formed GRP trims.
Who it's for
Anyone building or replacing an extension, dormer, bay roof, porch or balcony where a seamless, walk-on finish is required.
When you need it
New builds, extensions and full flat-roof replacements — GRP is not a repair medium for aged felt.
Why professional matters
GRP has no seams, no laps and no adhesives that fail. It bonds molecularly to itself and to preformed trims. When installed on a correctly-falled, dry OSB3 deck by trained roofers, it is the longest-lasting domestic flat-roof option available.
What happens if you leave it
Damage escalation
- GRP failures almost always trace back to a wet deck at install or crystalline movement in the substrate — problems that get worse, not better, if ignored.
- Delaminating topcoat exposes the laminate to UV; UV chalks the resin, which then absorbs water.
- Cracked internal corners under upstands let water into the wall cavity, where you may not see it for a year.
Common mistakes
- Laminating over a damp or contaminated deck — the bond fails within a season.
- Using a single layer of matting on walked-on terraces instead of the required two layers.
- Skipping pre-formed trims to save cost, then trying to laminate a sharp corner in-situ.
How we deliver the work
Inspection
Deck and detail survey — free written quote with the exact spec, no upsell.
Strip & deck
Old covering removed, deck replaced or over-boarded with 18mm OSB3, falls corrected.
Trims
Pre-formed GRP drip trims, raised edge trims and internal / external corners mechanically fixed.
Laminate
Two layers of 450g CSM (chopped strand matting) laminated in catalysed resin, rolled to eliminate air voids, cured to touch before topcoat.
Topcoat & sign-off
Pigmented topcoat applied in your chosen colour (light grey standard), water-test, walk-around and 10-year insurance-backed guarantee registered.
What you get from booking RTC
Seamless
One continuous membrane — no joints, no seams, no adhesives to age.
Walk-on finish
Fully trafficable when correctly specified — ideal for balconies, terraces and roof-access hatches.
25-year design life
Correctly laminated GRP roofs are documented to last 25+ years with minimal maintenance.
Colour choice
Standard light grey, or specify dark grey, sandstone or slate to match your setting.
10-year insurance-backed guarantee
HomePro protection valid even if we cease trading.
£5M insured
Public and employers' liability at £5M each — certificates on request.
Materials, methods & specifications
Substrate — why 18mm OSB3
OSB3 is a moisture-resistant board designed for humid conditions. Standard chipboard swells and delaminates, taking the GRP with it. We over-board or replace decking as needed and never laminate over marine ply unless specifically detailed.
Two-layer lamination
Two 450g CSM layers is the industry standard for domestic. Balconies and terraces get an additional detail layer at high-wear zones. Rollers consolidate matting until fully transparent — no white patches means no air voids.
Trim system
Pre-formed drip, raised-edge, internal and external GRP trims mechanically fix to the deck and laminate integrally into the membrane. This is the detail cheaper installations skip.
Topcoat & maintenance
The pigmented topcoat is UV-stable and sacrificial. Recoating at year 12–15 doubles roof life without disturbing the laminate — planned maintenance, not repair.
GRP vs EPDM
GRP wins for walked-on surfaces, complex shapes and edge detailing. EPDM wins for large simple rectangles and where budget is critical. We quote whichever is right for the roof — not whichever pays more commission.
GRP Roofing — your questions answered
How long does a GRP roof last?+
A correctly-installed GRP roof has a documented life expectancy of 25 years or more, with a topcoat refresh at around year 12–15 to extend life further.
Can I walk on a GRP roof?+
Yes — GRP is fully trafficable when correctly specified. For balconies and terraces we add an anti-slip aggregate to the topcoat.
How much does GRP roofing cost?+
Every job is quoted free, fixed-price and itemised in writing after a no-obligation inspection — costs vary by pitch, access, materials and scope, so call 0800 043 1108 or request a free quote for a firm figure.
Can GRP be installed in winter?+
Yes, above 5°C and on a dry deck. Our resins are catalysed to the day's temperature. Rain within the cure window is the risk, so we monitor forecasts and use temporary weathering when needed.
Will it crack in the cold?+
Properly-installed GRP does not crack from thermal movement alone. Cracks trace to substrate movement or missed lamination — both avoidable at install.
What colours are available?+
Standard light grey is included; dark grey, sandstone, slate grey and other RAL pigments are available on request at no extra cost on quotes.
What guarantee do you offer?+
10-year HomePro insurance-backed guarantee on qualifying installs, plus manufacturer product warranty on the resin system.
Do you provide GRP repairs?+
Yes — for damaged sections, roof-lantern reseals and topcoat refresh work. Call the office or the mobile line for urgent work.
Flat Roofing
Modern flat roof systems built to shed water and last.
Learn moreRe-Roofing
Pitched & flat full replacements with 10-year guarantee.
Learn moreRoof Repairs
Fast, honest repairs — slipped slates to storm damage.
Learn moreGet a free, fixed-price quote for grp roofing
Free inspection, itemised written quote, 10-year insurance-backed guarantee on qualifying installs. No pressure, no call-out charge.
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