GRP fibreglass (also called FRP) is one of the most popular flat roofing systems for domestic extensions and garages, and a key reason is its longevity. A properly installed GRP flat roof is typically expected to perform for 25 years or more with reasonable care. But that lifespan depends on two things above all: the quality of the installation and the condition of the deck beneath it.
Why installation quality matters
GRP is a seamless, liquid-applied system reinforced with glass mat. It has to be mixed, laid and cured correctly to achieve its full strength and weather resistance. Poor mixing, inadequate reinforcement or rushed detailing at edges and trims all shorten the life. That is why specialist installation matters — see our flat roofing page.
The deck beneath
GRP needs a solid, dry, well-prepared deck — usually OSB3 boards. A wet or flexing deck causes the fibreglass to crack, so we always assess and prepare the deck properly before laying a new system.
Falls and drainage
Standing water is the enemy of any flat roof. Correct falls so water drains to the gutter, not ponds, are essential to a long-lasting GRP roof. We address the falls as part of any installation.
Maintenance
GRP is low maintenance. Keep it clear of debris, check the edge trims occasionally, and have it inspected if you notice any cracking or blistering. A well-cared-for fibreglass roof gives many years of trouble-free service.
Is a fibreglass roof right for you?
GRP is an excellent choice for domestic flat roofs where a seamless, long-life finish is wanted. We assess your roof, its use and access and recommend the right system — GRP, torch-on felt or EPDM rubber. Arrange a survey through our quote form.
Frequently asked questions
How long does a GRP fibreglass roof last?
A properly installed GRP fibreglass flat roof is typically expected to perform for 25 years or more with reasonable care. Installation quality and a sound deck are the biggest factors.
Can you repair a fibreglass roof?
Yes, where the deck is sound. We repair cracks, blisters and failed detailing in GRP roofs. If the deck or covering has failed broadly, we recommend a replacement and quote for it.