GRP Flat Roofs Explained

GRP Flat Roof

GRP or Fibreglass roofing is one of the best, reliable ways to weatherproof flat, pitched or barrel-vaulted roofs.

Its low-maintenance and quality materials make it one of the most cost-effective roofing methods available.

What does a GRP roof involve?

Materials Needed to Install

To install a GRP flat roof (Glass Reinforced Plastic), you’ll need the following materials:

  • Roofing Resin

  • Fibreglass Matting

  • Roofing Topcoat

  • GRP Roofing Trims

  • Ancillary Tools (rollers, brushes, mixing buckets, etc.)

Benefits of a GRP Flat Roof

Once fully cured, a GRP flat roof is:

  • Seamless and waterproof

  • Low-maintenance – it won’t rot or emit odours like some traditional materials

  • Resistant to moss and algae

  • Easy to clean – just use a brush, mop, or hose

Installation Overview

Fibreglass roofing involves applying layers of glass mat soaked in resin across the roof surface. Once cured, this forms a strong, seamless, and fully waterproof barrier.

Matting Guidelines:

  • 450g glass mat – suitable for roofs with no foot traffic.

  • 600g glass mat – ideal for areas with light footfall.

  • 900g or two layers of 450g – recommended for balconies or areas with heavy footfall.

After the resin cures, a Roofing Topcoat is applied. This topcoat not only gives the roof its final colour but also seals the fibreglass to create a tack-free finish. If the roof needs to be walked on, a non-slip topcoat is recommended. For fire resistance, the topcoat should be applied at a coverage rate of 0.8kg/m².

Advantages of a GRP Flat Roof

A GRP flat roof (Glass Reinforced Plastic) offers numerous benefits, making it a smart choice for both residential and commercial buildings. Here’s why:

  • Safer Installations
    Unlike other roofing systems, GRP roofing doesn’t require complex machinery or heat equipment. As a result, the installation process is not only quicker but also much safer, significantly lowering the risk of on-site accidents.

  • Exceptional Durability and Strength
    When installed correctly, a fibreglass roof typically lasts over 20 years. This impressive lifespan offers outstanding long-term value and peace of mind.

  • Versatile and Flexible
    GRP systems include a wide range of trims to suit different roof types. Furthermore, materials can be easily cut and shaped to match unique layouts, giving you more freedom during installation.

  • Seamless Waterproofing
    Because GRP flat roofs are installed as a single, continuous layer, they eliminate common leak points found in traditional roofing. This seamless design ensures a fully waterproof and reliable finish.

  • Highly Weather Resistant
    In addition, the topcoat provides an added layer of protection, making your roof highly resistant to rain, snow, UV rays, and general weathering.

  • Low Maintenance and Easy to Repair
    Keeping a GRP flat roof clean couldn’t be easier—simply brush, hose, or mop the surface. And if damage ever occurs, minor repairs are straightforward and cost-effective.

GRP Roofing Applications

Fibreglass Roofing is suitable for both domestic and commercial use. In commercial applications it is used for schools, hospitals and office blocks.

For domestic purposes it can be used for extensions, sheds, garages, porches and balconies (with non-slip topcoat) to name but a few.

Why choose TriRoof for your GRP flat roof materials?

TriRoof has over 60 years’ experience in the fibreglass industry. We have first-hand experience in dealing with many customer projects in relation to flat roofing. This experience has given us an unrivalled knowledge of the best products for fibreglass roofing applications.

We don’t cut corners when it comes to your roof. As a leading supplier in the fibreglass industry, we know that quality counts.

Our Premium Roofing Kits offer a fire retardant Roofing Topcoat which complies with BS 476 Part 3: 2004 and is available in Dark Grey. Our premium flexible Roofing Resin will aid thermal expansions/contractions, roof settling and slight movement in roof flexing due to walking on the roof.

GRP Roofing Edgings and Trims will give your roof a decorative and professional finish.

Once used correctly, a combination of these materials will leave you with a seamless, waterproof flat roof.

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