Flat roofing
GRP fibreglass roofing
Glass fibre matting laid into resin and cured in place, producing one continuous laminate with no joints anywhere — including at the upstands and around the outlets. It sets hard enough to walk on.
How a GRP roof is built
- The deck is replaced or overlaid with roofing-grade OSB — GRP is rigid, so it needs a stable, properly fixed substrate underneath it.
- Edge and drip trims are fitted and bonded in, forming the perimeter the laminate ties into.
- Glass matting is laid and wetted out with catalysed resin, consolidated to remove air, and left to cure.
- A pigmented topcoat is applied, which gives the finished colour and the ultraviolet protection.
Where it suits
Balconies, roof terraces, dormer tops and anywhere a hard, walkable, genuinely seamless surface is wanted. It takes foot traffic that would damage EPDM, and it can be finished with a non-slip aggregate where it is being walked on regularly.
What to watch
It is the least forgiving system to install. It needs dry weather and a temperature range to cure properly, so it is a poor choice in a cold snap or on a wet week. It is also rigid: a deck that moves or deflects will crack a laminate that is otherwise perfect. Where a deck is suspect, GRP is the wrong system rather than a system that needs more care.
We use Cure It GRP systems. Deck preparation is the part of a GRP quotation worth reading closely.
GRP questions
Can GRP be laid over my existing flat roof?
Not over felt or rubber. GRP needs a clean, dry, rigid timber substrate, so an existing covering comes off and, in most cases, a new deck goes down. That is a real cost difference against a system that can sometimes overlay, and it should be on the quotation rather than discovered on the first day.
Why can it not be installed in winter?
The resin cures chemically and needs both temperature and dry conditions to do it. Rain on an uncured laminate ruins it. It can be done in cooler weather with the right catalyst ratio and protection, but there are days when the honest answer is to wait — and a roofer who says so is telling you something useful.
Not sure what your roof needs?
An inspection ends with a written report and photographs, whether or not you go ahead with the work.
Inspection fee: £99.00.