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Industry Experts

50 Years Experience

Finance Available

Spread the Cost

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Industry Experts

50 Years Experience

Finance Available

Spread the Cost


Benefits of GRP – Fibreglass Roofing

What is GRP Roofing?

GRP stands for glass reinforced plastic or more commonly known as fibreglass. A GRP roof is made up of several layers to create a laminate that then sets creating a watertight layer. The first layer is a polyester resin applied to the roof deck. This is then strengthened by applying a chopped strand matting which is made from glass fibres. Another layer of resin is then applied to fully soak the matting. A catalyst will be used within this polyester resin to ensure that the resin cures. Lastly a topcoat is applied to the roof to completely finish and protect the system. Top coats can be upgraded with slate grit to create a walkway finish which will reduce slipping on the roof.

A GRP flat roof provides a strong and lightweight alternative to the traditionally used lead or felt roofing alternatives.

The benefits of GRP fibreglass roofing

  • Extremely light weight
  • Versatile
  • Strong and durable
  • Life span of 15-40 years
  • Seamless finish
  • UV resistant
  • Weatherproof
  • Cost effective
  • Can be used with Green Roofs

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GRP is a very lightweight roofing system especially compared to felt and lead systems. This is because it is a thin system that is around 1mm - 2mm in thickness and will average out at approximately 1.5kg - 2.5kg per sq.m. In comparison to code 8 lead at around 40kg per sq.m and felt at approximately 15 - 25kg per sq.m, it is a considerably lighter product. This reduces the strain on the roof joist and overall structure. A lightweight system is crucial in many flat roofing projects which makes a fibreglass flat roof a great option within the industry.

GRP is a versatile product as it can be formed to any shape necessary making it ideal for complicated roofs where you might have soil vents, outlets and roofs with a skylight.

Many blogs and retailers will say that GRP is flexible but there is only one flexible GRP system on the market at the moment in RES-TEC’s Flexitec 2020. This system can be used on fresh OSB timber decks like other GRP systems and can also be used as an overlay system making GRP even more versatile than previously imaginable.

GRP roofs are strong and durable even when installed using the minimum matting size of 225g. This allows for light roof access. However, if you do require a system for high foot traffic, such as for a walkway or a balcony deck, you would need to use a more heavy-duty matting such as the 600g matting.

GRP roofing systems can also be used for balconies if used with an anti-slip grit which proves how strong fibreglass roof coverings really are.

Another reason a fibreglass roof is so durable is due to its puncture resistance quality.

As fibreglass roofing is applied wet it will mould to any roof shape no matter how complex and will leave a seamless finish. The matting can also be cut into any shape, such as to suit up-stands, which allows GRP systems to be used in conjunction with skylights.

The top coat used in a fibreglass roof is designed to cover the whole deck including the trims and joints. This seamless finish is the reason that many roofing contractors prefer to use fibreglass roofing. Not only does it look neat and professional it also reduces the time spent detailing around complex edges.


A GRP roof has a high resistance to UV. UV rays can affect some roofing systems by causing them to crack and blister over time however our GRP systems are UV stable.

Some fibreglass roof systems may fade over time from UV rays, however this will not cause damage to the roof and is purely an aesthetical issue, the ones UK Flat Roofing carry use modern materials and are fully UV Resistant.

Fibreglass roofing creates a thin, strong and waterproof layer over your roof deck by combining the strength of the glass fibre matting with the hard non-permeable layer of resin.

As there are no seams, once the roof is fully cured and installed correctly it is impenetrable to all weather conditions including snow, ice, wind and rain.

How much a GRP fibreglass roof costs is totally dependent on the system you choose and the strength you need.

For example, if you only need light access to the GRP flat roof then you would only need to use the 225g matting and a basic top coat thus reducing material costs. However, if you require a GRP roof covering for a walkway or balcony you would need the heavy duty 600g matting and an anti-slip grit top coat. This may increase material costs initially but the longevity of the fibreglass roof ensures that a GRP roof is cost effective.

Yes! A fibreglass flat roof is a fantastic system for use under a sedum or wildflower green roof. The seamless finish of a GRP roofing system means that the roots from the living roof installation above are unable to penetrate or damage the roof covering. This is also cost effective as there is no need for an expensive root barrier which is needed in older roofing systems such as felt.

Where are GRP fiberglass roofs typically installed?

  • Fibreglass Garage roofs
  • GRP Dormer Lining for gutters
  • Balcony flooring
  • Shed roofing
  • Extension roofs


Our brands of GRP include