What Can I Fibreglass Onto?

GRP fibreglass roofing is a system that is becoming more and more popular with new roofing projects and installation.

It provides a whole range of benefits over more traditional methods and can be applied over a number of different surfaces and still retain all its best features.

Not all surfaces are suitable for fibre glassing over, and some may need to be treated before becoming suitable. Take a look below to find out what materials are and aren’t suitable for GRP roofing.


Yes, it is possible to fibreglass onto plywood. This might be applicable if you have a shed or outhouse under construction, but you need a bit more reinforcement on the roof to keep bad weather away and the inside completely dry.

You’ll need the plywood to be fully dry, and may need to use two coats of resin before applying the fibreglass cloth depending on how porous the wood is.


Yes, you can fibreglass onto concrete. All you’ll need for this is the basic adhesive and resin, however you may want to clean the concrete surface of any oil to improve adhesion quality.

Again, the concrete should be clean and dry.


Again, lead is a yes when it comes to fibre glassing onto. It must be noted, however, that more often than not lead needs to be treated with primer first.

Lead can be covered with GRP, and in fact a lot of old roofs are made from lead and have been GRP fibre glassed over to update their leak proofing capabilities.


While it is technically possible to fibreglass over asbestos, this is a tricky and potentially dangerous material to work with. Although we encourage DIYing a lot of your projects, and encourage you with our guides and tips, we recommend any work involving asbestos be carried out by qualified professional contractors who have the recommended protective equipment and expertise to complete work involving this material.


It is not possible to fibreglass directly onto asphalt with standard resins. The thermal chemical reaction that occurs from fibreglass curing actually softens the asphalt, which hinders the bonding process between the materials.

Your options here are either to board over the asphalt, or use a polyurethane resin as opposed to traditional polyester resins, and combine this with a primer for the best results.


A flat and dry surface is always needed to fibreglass over, so the answer is no here, you cannot directly fibreglass over felt.

Again though, you can rip up and replace with, or overboard your felt with wood and fibreglass on top of this for the same end result.

Fibreglass is a very versatile product in terms of what it can be applied over. Some materials may need a little bit more preparation to make them suitable for application, but doing this prep right will result in the best possible finish and protection for your roof.

Shop GRP for the roofing materials you need to complete your project here.