GRP fibreglass roofing
GRP fibreglass cures into a single seamless membrane across the whole roof, up every upstand and into every outlet. There are no laps, no welds and no seams — so there is nothing for water to get under and nothing for the wind to lift. Dean is a RESTEC Flexitec 2020 approved installer, so the roof gets registered with the manufacturer when it is finished.
GRP — glass-reinforced polyester — goes on wet. Chopped strand matting is laid out over the deck, saturated with catalysed resin, rolled out until every air pocket is gone, and then left to cure. What you end up with is not a sheet laid on your roof; it is one continuous, rigid membrane bonded to it, formed in place around every edge and every detail.
That is the whole argument for it. Felt has laps. Single-ply has welded seams. Both are perfectly good systems, installed properly. But every joint is a decision someone made on a roof in the weather, and joints are where flat roofs leak. GRP simply does not have any.
It also cures hard. You can walk on it, put a ladder on it, stand a bin store on it, use it as a balcony floor. On a garage roof someone actually uses, or a dormer cheek that will get climbed on the next time the gutters need doing, that toughness matters more than the spec sheet suggests.
We fit a lot of it, and we still talk people out of it when the roof isn’t right for it. Here is the honest comparison.
Garages, dormers, balconies, porches, bay tops, small and mid-size extensions
Roofs on a sound timber deck, with plenty of edges and upstands to detail, that need a hard walkable surface. This is where GRP beats everything else comfortably.
Large single spans, and decks that flex or move
GRP is rigid. On a big, lively deck that moves seasonally, a flexible membrane copes better. On most domestic roofs this is not a factor — on a long garden-room span it can be.
Roofs that are sound underneath but leaking, and heavily detailed roofs
GRP wants a new, clean, dry timber deck to bond to. Where the existing roof is structurally fine and a strip-out would be wasteful, a cold-applied RESTEC liquid system gets you a seamless finish without the tear-off.
Wet or soft decks, and jobs booked in the wrong week
Resin needs dry conditions and around 5°C or above to cure properly. It cannot be laid onto damp timber. Anyone offering to fibreglass your roof in the rain is about to sell you a roof that fails, and we will move a date rather than do that.
A GRP roof is only as good as what it was laid on and how hard it was rolled. This is the specification we work to.
New moisture-resistant decking, screwed rather than nailed so it cannot lift, with a 3mm expansion gap between boards and falls built in so water drains rather than ponds. GRP is only ever as stable as the deck under it, so this is not the place to reuse tired timber.
Drip trims and edge trims fitted to every perimeter, then bonded and bandaged into the laminate rather than simply screwed on and relied upon. A trim that is only mechanically fixed is a joint, and we have just spent the whole page explaining what joints do.
Matting laid across the deck and up every upstand, saturated with catalysed resin and rolled until it goes clear. Rolling is the part that gets skipped when someone is rushing: any air left in the laminate is a dry patch, and a dry patch is a future blister.
A pigmented, UV-stable topcoat sealing the laminate as one continuous surface, in your choice of finish — dark grey is the usual, but it does not have to be. A non-slip aggregate can be worked into the topcoat where the roof will be walked on regularly.
A well-laid GRP roof is close to maintenance-free. When one does start to go, it tends to announce it in these ways.
GRP is unforgiving of a bad install, which is exactly why manufacturers train and approve the people allowed to fit their systems. It is worth asking anyone quoting you what they are approved for.
GRP is not the cheapest flat roof on day one and it is usually the cheapest across twenty years. What you actually pay comes down to these.
Free inspection, free written quotation, itemised, with the deck condition risk flagged before we start rather than discovered halfway through.
Get a Free QuoteRecent GRP and flat roofing jobs across Worthing and the surrounding postcodes.
A correctly laid GRP roof on a sound deck typically lasts 25 to 30 years, and manufacturers generally rate the systems in that range. The deciding factors are the deck it was bonded to, whether the laminate was properly consolidated, and how the edges and upstands were detailed — not the resin itself.
Yes. It cures rigid, which is one of the main reasons to choose it over a membrane. Where a roof is going to be walked on regularly — a balcony, a roof terrace, a garage roof with a ladder on it every autumn — we can work a non-slip aggregate into the topcoat so it stays safe when wet.
A typical garage or extension roof is two to three days: strip out and deck on day one, laminate on day two, topcoat and trims to finish. The resin needs dry conditions and around 5°C or above to cure, so we plan them around the weather rather than forcing them through it.
No, and be wary of anyone who says it can. GRP needs to bond to a clean, dry timber deck — laid over old felt it has nothing to key into, and any moisture trapped underneath will blister it. If you want a seamless finish without a full strip-out, the right answer is a cold-applied liquid system, which is designed to overlay.
The laminate itself does not, but it is rigid, so it can crack if the deck beneath it moves. That is a decking and fixing problem rather than a GRP problem, and it is why we lay new 18mm OSB3, screw it rather than nail it, and leave expansion gaps between boards.
Dark grey is the standard and by far the most common, but the topcoat is pigmented so other colours are available. If the roof is overlooked from a window above, it is worth thinking about — it is the view you will actually live with.
Two separate things, and it is worth knowing the difference. Ours is a written 5–10 year workmanship guarantee plus a leak-free guarantee on new installations. On top of that, Dean is a RESTEC Flexitec 2020 approved installer, which means your roof is registered with the manufacturer on completion and the materials carry RESTEC’s 20-year guarantee issued direct to you. That second one is only available through installers holding a current training ID, so it is a fair question to ask anyone quoting you.
Send a couple of photos and your postcode and Dean will come back to you personally, usually the same day, with an honest answer about whether fibreglass is the right call for your roof.
Tell us about the problem and Dean will come back to you personally, usually the same day.
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Garages, extensions, dormers, balconies and commercial roofs across Worthing and West Sussex. We survey the roof first, then specify the system that suits it — GRP fibreglass, EPDM rubber, single-ply membrane or a RESTEC liquid applied system.
Read moreLiquid applied roofing is a cold-applied, fibre-reinforced membrane that cures seamlessly over the whole roof — including every upstand, outlet and pipe. Dean is a RESTEC trained installer, so the system can carry manufacturer-backed cover as well as ours.
Read moreSlipped and broken tiles, failed ridges and verges, leaking valleys, chimneys and full strip-and-re-cover across Worthing and West Sussex. We get up on the roof and find the actual cause before we price anything — and where a repair genuinely solves it, a repair is what we will recommend.
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