What Is GRP Roofing?
GRP — glass-reinforced plastic, usually just called fibreglass — is a flat roofing system laid wet on site. A layer of resin and chopped-strand matting is rolled onto a new timber deck, then sealed with a coloured topcoat. It cures into one solid, completely seamless surface with no joints, no seams and nothing to peel back in the wind.
Why Choose GRP
- Seamless whatever the shape — upstands, corners, outlets and awkward details are simply laminated in, which is why GRP suits the complicated little roofs East London is full of
- Genuinely walkable — the right build-up takes regular foot traffic, making it the standard choice for balconies and roof terraces on warehouse conversions
- Crisp finish — pre-formed edge trims give a neat, gutter-ready edge that looks sharp from the street
- Long life — properly laid GRP systems are typically rated for 25–30+ years
GRP vs EPDM vs Felt
We fit all three, so you'll get a straight answer rather than a sales pitch. As a rule of thumb: GRP wins on complex shapes, balconies and anywhere that gets walked on; EPDM rubber wins on big, simple roofs and tighter budgets; and torch-on felt remains a sound, economical choice — see our flat roofing page for the full comparison.
The Catch: It Has to Be Laid Right
GRP is unforgiving of shortcuts. The resin needs a dry day and the right temperature, and the system needs a sound, fully boarded deck — usually new OSB3 — underneath. Cheap, rushed GRP jobs laid onto damp or flexing decks are why you see cracked and crazed fibreglass roofs only a few years old. We board properly, lay in the right conditions and never rush the cure.
GRP Roof Repairs
Cracks, crazing and pinholes in an otherwise sound GRP roof can often be repaired and re-topcoated rather than replaced — a fraction of the cost of a new roof. If water has got under the laminate we'll tell you honestly, with photos, and price both options. Got an active leak? See our roof leak repairs.
How Much Does a GRP Roof Cost?
As a rough guide, a new GRP roof in London typically lands around £90–£140 per square metre supplied and fitted, depending on deck condition, insulation requirements and edge details. Balconies and terraces with railings or paving cost more to detail properly. Every job gets a free survey and a fixed written quote before we start — call 020 4578 5836.