What makes a fibreglass roof different
GRP means glass reinforced plastic. Instead of a sheet that is rolled out and stuck down, a fibreglass roof is built on site: liquid resin is mixed with a catalyst, brushed onto the deck and a chopped-strand glass mat is rolled into it. As it cures, the resin and glass lock together into a rigid layer with no seams.
That hard surface is the main reason people choose it. A GRP flat roof copes with occasional foot traffic, suits balconies and roofs that need regular access, and can be finished in a range of topcoat colours rather than plain black.
Laying a GRP roof, step by step
Fibreglass is sensitive to damp and temperature while it cures, so we only laminate in suitable weather and protect the roof between stages. Get the conditions wrong and the laminate can fail to bond, so we would rather move a day than rush it.
- Strip the old covering and inspect the joists and deck
- Lay new OSB3 boards where needed, tightly fixed with joints taped
- Fit pre-formed GRP edge trims and drip trims around the perimeter
- Apply the resin and glass mat laminate across the deck and up the upstands
- Once cured, apply the topcoat to seal and colour the roof
What affects GRP roof cost
We do not list a price per square metre. A GRP roof cost depends on the area, but also on the number of trims, outlets, upstands and roof lights to detail around. Replacing rotten decking, adding insulation for a warm roof, access and skip hire all play a part. Lee prices each roof after a free visit, and your written quote lists what is included so you can compare like with like.
Fibreglass roof repairs and leak repair
GRP is durable, but it can still leak. Common causes are hairline cracks where the deck has moved underneath, a trim that was not bonded fully, damage from something heavy being dropped, or a topcoat that has worn thin on a roof that was walked on often.
Fibreglass roof leak repair usually means cutting back the damaged area, abrading the surrounding laminate and building it back up with fresh resin and matting, then topcoating to match. If the deck below has got wet and gone soft, that section has to be replaced first. Our flat roof repairs page explains how we decide between a patch and a larger repair.
If you are looking for fibreglass roof repairs near you in Essex, ring Lee and tell him where the water is getting in.
GRP or rubber?
Both are good systems. GRP gives a tougher, walkable finish and handles complicated shapes well. Rubber is flexible and very quick to lay on simple roofs. See our EPDM rubber roofing page and the GRP vs EPDM guide for a fuller comparison, or browse the main flat roofing page.
Looking after a fibreglass roof
GRP needs very little maintenance, but a quick look once or twice a year pays off. Clear leaves and silt from outlets and gutters so water does not sit at the edges, sweep off moss or debris that collects in corners, and keep heavy items such as plant pots or ladders off the surface unless it was built for foot traffic. If you notice crazing in the topcoat, a hairline crack or a trim pulling away, it is far easier to deal with early, before water reaches the boards underneath.