Just wrapped up a fibreglass roofing job in Coulsdon that shows exactly why GRP (glass reinforced plastic) is such a brilliant solution for flat roofs. The customer had been putting up with an old torch-on felt roof that had reached the end of its life, and they wanted something that would actually last this time.
Torch-on felt roofs are common enough, but they've got a shelf life. After 10 to 15 years, you're usually looking at repairs, and eventually, it makes more sense to replace the whole thing rather than keep patching it up. This particular roof had seen better days, with the felt starting to blister and crack. Water was getting through, and the decking underneath had taken some damage as well.
Starting from scratch
When we pulled up the old felt, it was clear the decking needed replacing too. There's no point putting a quality fibreglass roof over dodgy boards, so we stripped it right back to give ourselves a proper base to work from.
We fitted new 18mm tongue and groove OSB boards across the whole roof area. OSB (oriented strand board) is ideal for this because it's strong, dimensionally stable, and provides a smooth, solid surface for the fibreglass. The tongue and groove joints lock together nicely, so you don't get any movement or squeaking, and it all sits nice and flat.
Once the new decking was down and secured, we could start on the fibreglass system itself. First up were the trims and drip edges. These are crucial because they define where the fibreglass finishes and ensure water drains off properly without running back under the roof covering. Get these right at the start and everything else falls into place.
Laying the fibreglass
The fibreglass matting goes down next, embedded in the first coat of resin. This is where the real waterproofing happens. The matting and resin bond together to create a single, seamless layer that's completely watertight. Unlike felt or other membranes that are joined in sections, fibreglass forms one continuous surface with no seams or weak points where leaks can start.
We work methodically to avoid any air bubbles or dry spots in the matting. The resin needs to fully saturate the fibreglass, so you're rolling it out carefully and making sure there's good coverage right across the roof. It's not a job you can rush, but when it's done properly, you've got an incredibly tough, waterproof surface.
After the first coat had cured, we applied the topcoat. The customer chose grey resin for the finish, which looks smart and professional. The topcoat provides UV protection and gives you that final sealed surface that's going to stand up to whatever the weather throws at it.
Why fibreglass beats felt
There's a reason more and more people are choosing fibreglass over traditional felt for flat roofs. For a start, you're looking at a 20-year guarantee as standard, compared to maybe 10 years for torch-on felt if you're lucky. But the real lifespan of a fibreglass roof can be 30 years or more when it's installed correctly.
It's completely seamless, which means no joints to fail. It's incredibly strong and can handle foot traffic without damage. It's resistant to standing water, which is always a concern with flat roofs. And it requires virtually no maintenance once it's down.
The initial cost is higher than felt, there's no getting around that. But when you factor in how long it lasts and the fact you won't be calling someone out for repairs every few years, it works out cheaper in the long run. Our customer in Coulsdon understood this straight away. They'd had enough of patching up the old felt roof and wanted something they could rely on for decades.
Two days well spent
We completed the whole job in two days. Day one was removing the old felt and fitting the new decking. Day two was the fibreglass installation from start to finish. The customer was really pleased with how quickly we got it done without cutting any corners.
Fibreglass does need decent weather to install properly because the resin has to cure, so we always keep an eye on the forecast. You don't want to be caught out halfway through with rain coming in. Luckily, we had a good window and everything went smoothly.
The finished result
The roof looks brilliant now. That grey fibreglass finish is clean and modern, and more importantly, it's completely watertight and guaranteed for 20 years. The customer's got peace of mind knowing they won't be dealing with leaks or damage, and they've added value to their property with a quality roofing system.
If you've got an old felt roof that's causing you grief, or you're planning a new flat roof and want something that actually lasts, fibreglass is worth serious consideration. It's not the cheapest option upfront, but it's one of the best investments you can make in your property.
We're always happy to come out and assess what you need. Whether it's a small garage roof or a larger extension, fibreglass roofing gives you a professional, long-lasting finish that you can rely on. Get in touch for a straightforward quote and honest advice about what's best for your situation.
