FAQ - Frequently Asked Questions

What is a GRP Roof?

A GRP flat roof, or fiberglass roof as it's also known, is one of the most popular flat roofing solutions in the UK. GRP stands for Glass Reinforced Polyester, a composite material formed by strengthening plastic with fine fibres made of glass.

Is GRP the same as Fibreglass?

GRP and Fibreglass are the same thing. In fact, you might even hear the term “glass fibre” being used by some contractors. ... This stands for fibre reinforced plastic or fibre reinforced polymer.

What is GRP Resin?

Glass Reinforced Polyester (GRP) is, as the name suggests, a polyester material reinforced with the addition of glass fibre (also commonly known as fibreglass). The material is produced by combining thermosetting polyester resin and glass fibres under strictly controlled factory conditions.

Is GRP/fibreglass roofing better than felt?

GRP/Fibreglass is a newer roofing system that lends itself best to flat roofing but is also suitable for pitched roofs in some applications. Fibreglass is much more durable than felt and stronger too. ... A fibreglass roof will last for more than 20 years and it's less likely than felt to develop a fault.

Can you walk on a GRP/Fibreglass roof?

Yes, a GRP/Fibreglass Roof can be walked on. ... A roof with little to no foot traffic expected would suit 1 layer of 450g matting, a moderate level of foot traffic should use 1 layer of 600g matting and a balcony or a roof with regular foot traffic should use 2 layers of 450g matting.

Do GRP’s roof’s crack?

This most often happens if the topcoat is applied too quickly or on top of still-wet laminate.Reapplying the topcoat can fix any problems with flaking or cracking on the surface of the roof.

Like all roofs, the gutters of your GRP roof can susceptible to problems if they are not regularly maintained. This is more common in flat roofs that are closer to the ground, as they are prone to debris, and leaves finding their way into the gutter. Ensure you clean out the gutter every season to stop blockages, which leads to water build-ups that can cause leaks into the roof.

GRP roofs remain popular thanks to the strength of fibreglass. With high tensile strength, great insulation, fire and water resistance, the perfect solution for any flat roofing property.

Are GRP roof’s noisy?

When a roof heats up and cools down during the course of a day, it will make noise, this is due to thermal expansion and contraction and is a completely normal process. 

Can you recoat a GRP roof?

Repairs should be made by cutting out the damaged section and grinding the surrounding area to a roughened, feathered surface extending 100 mm in each direction from the damaged area. The area to be covered should be thoroughly cleaned with a stiff brush. Glass mat and CrysticRoof Resin should be used to make good the repair, left to harden and subsequently the CrysticRoof Topcoat re-applied. Care should be taken not to coat existing areas of Topcoat.

How long will a GRP roof last?

A properly laid fibreglass roof also known as GRP Roofing, will last for at least 30 years with no measurable deterioration.

CrysticRoof Resin offes a 10-15 year guarantee and the perfect GRP resin to ensure the durability of your roof.

How Strong is GRP?

GRP has a high strength to weight ratio and high flexural strength, this means it is a lightweight material that is also super strong. Pound for pound GRP can be stronger than steel!

It also allows for less material to be used than traditional structural materials thus lowering cost and weight. Therefore glass reinforced plastic will act as a satisfactory solution to the corrosion problems and come at a very affordable cost.

Can I fibreglass in the rain?

No. Always lay GRP roofs in dry conditions. If it has rained after laying the resin or the deck always make sure that the surface is fully dried before top-coating.

If it starts to rain, stop immediately and cover the roof with a tarpaulin or visqueen sheet. Keep the roof as sheltered as possible. The decking or the resin will need to be completely dry before continuing.

If you are unable to laminate over a prepared decked before it will rain, then coat the decking with catalysed resin and cover any exposed edges. This will seal the deck and prevent moisture ingress into the deck until the laminate can be applied.

After rain stops, use cloths to soak up water, and speed up the drying process by wiping with acetone.

How long does GRP resin take to dry?

At room temperature this will give a working time of 20 minutes before the resin starts to cure/harden. The joints and corners of the roof should be applied first.

Where to purchase GRP/Fibreglass repair materials?

GRPShop.co.uk supply a complete and comprehensive range of professional fibreglass repair products. These range from individual materials such as CrysticRoor Resin, CrysticRoof Topcoat, tools and trims.

If you have any other questions or queries relating to fibreglass/GRP roof repair, please don’t hesitate to contact us directly.