GRP Fibreglass Roofing

Laid wet, cured solid — one rigid waterproof skin you can walk on.

GRP — glass-reinforced plastic — is laid as liquid resin and glass matting over a new timber deck, then cures into one continuous rigid skin, finished with a coloured, UV-stable topcoat. Because it's formed in place, it flows around upstands, corners, outlets and awkward shapes without a single joint — and once cured it's tough enough to walk on routinely.

That combination sets its territory: balconies and terraces, flat roofs with regular foot access, and complicated roofs where a sheet membrane would spend its life at the mercy of its many joints. It's also simply a very good covering for ordinary extensions, with a 25-year-plus life and a crisp, finished appearance available in several colours (grey being the classic).

GRP's honest requirements: it's laid onto a new OSB deck (part of every proper GRP quote), it wants dry weather to cure, and on very large uninterrupted roofs, thermal movement needs designing for — where a sheet system may serve better. Right roof, right system.

Benefits

Why choose GRP Fibreglass Roofing

Fully seamless, formed in place around any shape
Genuinely walkable — suits balconies and terraces
25+ year life with a UV-stable topcoat
Crisp finished appearance, colour options
No flames during installation

Features

What's included

Wet-lay resin and glass matting systems
New OSB deck included in installation
Preformed edge trims and drips
Non-slip finishes for walked surfaces
Topcoat refresh option extends life further

Typical lifespan

25+ years

Done properly, with the right materials — the honest numbers are in our roof lifespan guide.

Repair options

Repair or replace

GRP faults are usually visible and specific: hairline cracks at trims or upstands where movement concentrated, or a worn topcoat on older roofs. Both repair honestly — cracks are ground back and re-laminated, and a tired-but-sound GRP roof can be re-topcoated to extend its life at a fraction of replacement cost. Widespread cracking or a flexing deck beneath is the sign to stop patching; see flat roof repairs for how we make that call.

Common questions

Frequently asked

GRP or EPDM for my extension? +

Both are excellent, so let the roof decide: simple rectangle, no foot traffic → EPDM's seamless sheet is hard to beat. Walked-on, complicated, or lots of upstands and outlets → GRP's formed-in-place skin wins. Price is usually close; we'll quote whichever fits, or both.

Why does GRP need a new deck? +

The resin bonds to and depends on a stable, dry, smooth substrate — laying it over old felt or a tired deck builds the new roof on the old roof's problems. Fresh OSB is part of the system, not an extra; a GRP quote without it is a corner cut.

Can GRP be done in winter? +

It needs dry conditions and workable temperatures to cure properly, so winter installs are possible but weather-dependent — we plan them around forecasts and won't lay resin into rain or heavy frost. EPDM is less fussy if the calendar can't move.