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Welcome to Guaranteed GRP

Guaranteed GRP provide GRP Roofing systems to both residential and commercial customers. We are a roofing and waterproofing company which specialises in GRP Fibreglass Systems. This includes fibreglass flat roof installations, flat roof replacement and fibreglass roof repair.

For any GRP needs we have a team of specialist tradesmen to help provide you with a solution. All our tradesmen are fully qualified professionals. And we provide insurance backed guaranteed for all the GRP Fibreglass work we undertake.

If you need any information about anything relating to GRP and fibreglass or would like a quotation please get in touch today and one of our friendly team will be delighted to assist you.

What is GRP Roofing?

GRP Roofing has become a very popular roofing system over the last 30 years. It is interchangeably referred to as Fibreglass roofing. GRP as a product was developed in 1938, it was used as an insulation also known as FRP (fibre reinforced polymer).

As the years have gone on fibreglass manufactures have risen to the challenge and have now come up with a roof system that is not only one of the best-looking roofing systems. But also, a system that is robust and with BBA of up to 40 years’ materials and workmanship guarantee. Additionally, fibreglass has a proven pedigree as a waterproofing material with an expected lifespan of 100 years plus.

Nearly all the GRP roof systems have a BBA, this means that they are independently tested and verified. Fibreglass roofing is an ideal product for the roofs on new homes and the refurbishment of existing roofing systems.

A GRP Roofing System is normally a 3 Part Product


GRP roofing systems are normally a 3-part product with liquid roof resin/ reinforced matting and then a further coat of resin. With edge trims and a UV coating to finish.

If needed an extra traction coat can be added to provide anti-slip properties.

As a product, GRP/Fibreglass is very rigid board. This means it is important a GRP system is to be fixed leaving side gaps in case of timber swelling due to moisture exposure.

A Fibreglass Roof can be Finished in a Range of Colours

The finish of a fibreglass roof is very pleasing to the eye. The UV top coat can come in a range of colours (any RAL colour on the market). Below are some of the colours which can be used as the top coat to finish a fibreglass roofing project.


GRP Fibreglass Roof Benefits

• As GRP is completely seamless this is suitable for water containment such as ponds, swimming pools and all types of green roofing specifications.

• As the system is low skill to install most homeowners can install the full system, being cold applied this makes the GRP roof very pleasing to contractors and builders within the construction framework.

• GRP roofing is so robust that the system can be applied to walkways and can be applied over existing surfaces such as concrete, asphalt and felt coverings. With the correct primer, this not only keeps the building from the threat of water ingress it is environmentally friendly by not filling landfill with unnecessary waste.

• A traction foot coat can be added on top of the UV protection coating.

• GRP has a proven track record and will be around for many years to come.


Which Is The Best GRP Roofing System?

There are many great GRP Roofing systems products on the market. All of which have their own unique strengths and leave a seamless watertight finish.


UltraFlex is a highly flexible system which can move in line with the natural movements of the roof. This sets it aside from other GRP roofing systems which are very rigid and can sometimes crack under natural movements. Another benefit offered by UltraFlex is it is a self-terminating product and unlike other GRP products does not require a flashing detail.


Topseal systems offer a 40-year guarantee for their double top systems and various different guarantees for their ‘Green Roof’ systems. Another benefit of Topseal’s GRP product is it is possible to have a Topseal GRP roof in any RAL colour.


Polyroof have come a long way and are now amongst the leaders in GRP roofing. Their stand-alone system has a number of benefits. And has won a number of national awards.

Cure It, Tough Stuff and Pro GRP

These three GRP systems hold their own with the other systems mentioned and have their own unique strengths. They also all offer guarantees of between 20 and 25 years.

GRP Services We Provide


GRP Flat Roofing

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GRP Steps

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GRP Waterproofing

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GRP Roofing Trims

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GRP Flooring

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GRP Canopy

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GRP Podium Steps

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GRP Paint

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GRP Dormers

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GRP Valleys

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GRP Gutters

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GRP Roof Replacements

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GRP Substation

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GRP Stair Treads

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GRP Surveys

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Our Recently Completed GRP Roofing Projects


GRP Flat Roof Replacement


Commercial GRP Roofing


GRP Flat Roofing London


GRP Roof Walkway London

Frequently Asked Questions About GRP Roofing

Can You Walk On A Fibreglass Roof?

Yes, you can walk on a fibreglass roof if it has been installed correctly by an experienced tradesman. Fibreglass roofing is only vulnerable to damage via foot traffic if it has been installed incorrectly. This can lead to the roof cracking due to the pressure and strain incurred by the weight of a human body. With the proper installation, this problem is completely eliminated and you can safely walk on a fibreglass roof.

Can A Fibreglass Roof Be Repaired?

Yes, a fibreglass roof can be repaired in most cases. For example, if there is a pinhole present on the roof’s surface. This problem can be fixed simply by applying resin to the hole. Another example would be if there were visible cracks on the roof surface. If this was the case the affected area would need to be cut out and replaced entirely.

What Our Customers Say About Us

Latest from our Blog

Check out the latest from our blog. It covers everything to do with GRP/Fibreglass roofing and waterproofing including topics such as common fibreglass flat roof problems, comparisons of GRP with other systems and GRP installation guides.