Fibreglass GRP flat roofs in Kerry, Cork and Limerick
Glass reinforced polyester laid wet over a ply deck and cured into one seamless skin. No joints and no seams, and the trims are built into the same layer.
Also called fibreglass roofing, a GRP flat roof or a fibreglass flat roof for extensions, dormers and balconies.
Updated September 2026
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Roofs this suits
Small and medium flat roofs
Balconies and walk on decks
Dormer tops and bay roofs
Roofs where a seamless finish matters
Needs dry weather to lay, so we book it around the forecast.
What you get for the money
One seamless skin, no joints to fail
Walkable once cured, good for balconies
Trims are part of the same layer
Needs dry weather to lay and a sound ply deck underneath.
Fibreglass GRP, in numbers
Typical life
25 to 30 years on a correctly laid deck, and it comes with a manufacturer-backed guarantee
Deck required
New 18 mm WBP ply, screwed at 300 centres. GRP will not go over felt, chipboard or a soft deck
Minimum fall
1 in 80, and we build in 1 in 40 so deflection does not take it out
Weather window
Needs a dry deck and above about 5 degrees to cure. We book it around the forecast rather than promising a date and hoping
Fitted price guide
Roughly EUR 90 to EUR 140 per square metre including the new deck, scaffold on top
Walkable
Yes, once cured. Add a grit finish for a roof you will actually use
Guide figures for the south west. A small dormer or bay costs more per square metre than a garage roof, because the trims and upstands are the work.
One skin, no seams, and why the deck decides it
GRP is laid wet: resin, chopped strand mat, resin again, and then a coloured topcoat over the lot. It cures into a single continuous skin with the trims bonded into the same layer, so there is no joint anywhere on the roof for water to work at. On a small complicated roof with upstands and a bay, that is worth a lot.
What it will not tolerate is a bad deck. GRP is rigid, so any movement underneath cracks it. That means new 18 mm WBP ply screwed down, never nailed, and never laid over the old felt to save a day. If somebody quotes you GRP over your existing covering, that is the quote to walk away from.
The other honest limit is weather. It needs a dry deck and a reasonable temperature to cure, which in a Kerry November is not a given. We tent it where we can and otherwise we move the date, because a roof laid onto damp ply will blister and there is no fixing that afterwards. When the forecast will not play ball, Lava 20 is the system that will still go down.
Already have a fibreglass roof that is cracking? Read how we handle fibreglass flat roof repair, and if there is a rooflight in it, skylight replacement is best done in the same job.
Fibreglass GRP, asked and answered
Can GRP be laid in winter?
It can, on a dry day with the temperature up and the deck properly dry. What we will not do is lay it onto damp ply to hit a date, because it blisters and then it all comes off again. If the weather will not settle we will say so and offer you a liquid system instead.
Can you lay GRP over my old felt roof?
No. It needs a new ply deck screwed down underneath. Anyone offering to lay it straight over felt is giving you a roof that will crack at every seam under it within a couple of years.
Can you walk on a fibreglass roof?
Yes, once it has cured, and it is one of the better choices for a balcony or a roof terrace for that reason. If it is going to get real foot traffic we put a grit topcoat on so it is not lethal when wet.
GRP or EPDM rubber for my extension?
GRP for small, complicated roofs with lots of trims and upstands, and where you want to walk on it. EPDM for large simple rectangles, and it does not care about the weather on the day. We will tell you which of the two your roof actually is.
How much does a GRP flat roof cost?
New GRP including the ply deck is typically €80 to €120 per m². A 30 to 40 m² rear extension usually comes to €3,800 to €6,500, depending on trims, upstands and access.
We work with what suits the building
Not sure which material suits your roof?
Send us the address and a couple of photos. We will tell you straight what the roof needs, what it costs and how long it takes.