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GRP Roof

What is a GRP Roof?

First things first…

GRP stands for Glass Reinforced Plastic. GRP is strong, lightweight and resilient to weathering. Perfect for constructing a roof!

A GRP Roof is generally a flat roof made from a system of Resin, Fibreglass matting and Topcoat. When the components are put together the result will be a seamless, waterproof roof. Once all materials are applied correctly, a Flat Roof can last in excess of 20 years with little or no maintenance required.

Is a Flat Roof suitable for a DIY Project?

There are plenty of guidelines online including the FibreGlassDirect Flat Roofing Guidelines.

Each step requires plenty of prep work and can be undertaken by both DIY Enthusiasts and Professionals. As always, if in doubt seek professional advice from an experienced roofer.

How do I use the GRP Materials?

Wooden Decking

The first step in building any GRP Roof is securing the decking. We recommend OSB3 Boards. If you are applying a GRP Roof to an existing roof, inspect the existing decking. If it has signs of rot – replace it!

All boards must be secured with galvanised nails as they will not rust.

GRP Roofing Trims

Roofing Trims are necessary as they will help the water run-off from the roof. They will also give your roof a neat and decorative finish.

There are different types and lengths of Roofing Trims depending on where they will be located on the roof.

Resin and Glass

Roll out the glass on the roof. Cut the glass to size and roll back up until ready for use. Ensure that it is close at hand to use straight away when you have mixed the resin.

Resin should be mixed in batches of no more than 2kg at a time with 2% catalyst.

We normally work to a ratio of 3:1 – one third of the resin should be applied to the board and two thirds to the mat. Work through the mat with a brush and then consolidate with a roller to ensure no air pockets remain.

The mat should be transparent by the end of the laminating process and allowed to cure.

After the resin is cured the area should be sanded to remove and glass sticking up.


Once cured, Topcoat should be applied within 24 hours. Topcoat is the final layer of the GRP Roof project. This will provide the waterproof finish to protect your roof.

Topcoat is mixed with 2% Catalyst addition and applied with a brush. Topcoat is applied at approximately 0.8kg per 1sqm. This is the ratio that we work to within our Fibreglass Roofing Kits to achieve increased fire resistance.

Where to buy GRP Roofing Materials?

FibreGlassDirect has been providing GRP Roofing Kits and Materials for over 30 years. 

We provide a complete range of Low Cost and Premium Roofing Kits up to 100sqm which include Resin, Fibreglass Mat, Topcoat and Tools.

GRP Roofing from FibreGlassDirect