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When it comes to installing a durable and waterproof flat roof, GRP (Glass Reinforced Plastic) fibreglass roofing kits are one of the most trusted and long-lasting solutions. Whether you're working on a home extension, garage, balcony or commercial property, there's a GRP fibreglass roofing kit out there to suit your needs...
Fibreglass roofing kits are renowned for their seamless finish, long life expectancy - often 20 years or more - and minimal maintenance requirements. Unlike felt or bitumen systems, GRP roof systems don’t have seams or joints that can fail over time, which is ideal for both small or large, simple or more involved and complex roofing jobs.
They also offer impressive resistance to weathering, UV degradation and chemical exposure, making them a top choice for flat roofs in both residential and industrial settings.
All-in-one GRP fibreglass roofing kits contain professional-grade materials to create a complete roofing system. Alternatives such as fire-rated systems have been specially put together to meet specific fire safety standards, including resistance to ignition, flame spread and smoke production.
GRP roofing kits are therefore a serious go-to for tradespeople and contractors looking to meet both cost factors and the pressures of building regulation compliance, without compromising on the overall finish quality. These systems help streamline labour, reduce call-backs and deliver long-term performance that you and your clients can trust.
Plus, modern GRP kits are DIY-friendly, making them suitable for confident homeowners looking to create a straightforward, durable and reliable roof system. When choosing a GRP fibreglass roofing kit, you're typically looking at 3 essential options: Standard, 2-Layer or Fire-Rated.
But how do I know which one is right for me?
In this guide, Fibreglass Supplies Ltd break down the features, benefits and ideal applications of the most popular fibreglass roofing kits we have to offer, helping you choose your kit with confidence.
Whether you're working on a domestic garage or extension, a walkable balcony or roof terrace, or a commercial flat roof in need of essential fire protection, there’s a fibreglass kit for every job. The main differences between the different GRP roofing kits is the thickness of the matting (measured in grams per square metre), the type of topcoat used (standard or fire-retardant), and the number of layers required, based on foot traffic or regulations.
Let’s explore the main options available in our GRP Fibreglass Roofing Kits range...
The Standard 450g Fibreglass Roofing Kit is an excellent choice for a wide range of domestic flat roofing projects where foot traffic is minimal or occasional. It uses a 450g/m² chopped strand mat (CSM) which is ideal for standard, all-round, everyday durability in projects that prioritise ease of use and affordability.
This kit is a reliable waterproofing solution that is suited to any home or garden DIY project that doesn't require any major or heavy-duty reinforcement.
We recommend using the 'standard' in non-habitable outbuildings such as:
Because of its single-layer laminate design, the 450g kit is relatively lightweight and easy to apply, especially in dry and mild weather conditions. It offers a seamless, joint-free finish, which eliminates the risk of leaks over time and ensures long-lasting protection against rain, frost and UV rays.
What's Included?
Why Choose A Standard Kit?
One of the key advantages of using this kit is its DIY-friendliness. Whether you're tackling your first fibreglass job or looking for a straightforward system to install over OSB3 decking, this product makes the process accessible without compromising quality. If your roof isn’t walked on frequently and doesn’t require fire certification or slip resistance, the standard kit offers excellent value for money while still delivering professional-grade performance.
The 2-Layer 450g Kit is specifically engineered for roofing areas that experience frequent foot traffic and therefore require enhanced durability - making it ideal for balconies, roof terraces communal walkways and accessible flat roofs. Unlike standard single-layer systems, this kit includes two full layers of 450g chopped strand matting which means that the weight of fibreglass matting per square metre is 900g. The heavier the matting the stronger the roof is. The 2-layer construction will therefore significantly increases the overall strength and structural resilience of the fibreglass laminate.
This dual-layer construction ensures that the roof surface can withstand repeated use without cracking, splitting or showing signs of wear, making it a reliable option for residential or light commercial applications where people regularly walk, stand or place furniture or equipment.
We recommend using this 2-layer kit for the following projects:
What's Included?
This kit typically contains:
Why Choose The 2-Layer Kit?
Whether you're upgrading a balcony or installing a new roof terrace, this kit provides a professional-grade finish with the peace of mind that it will endure regular use while remaining watertight and maintenance-free for years.
If your project involves roofing over a habitable space - such as an extension, living area or any part of a building where people live or work - then our Fire Rated 600g Premium GRP Kit is the most appropriate and compliant solution. This high-performance kit is also essential for any flat roof installation where UK building regulations require fire resistance, such as in commercial builds, schools or shared residential structures.
The system features a heavy-duty 600g/m² chopped strand mat, which provides a much thicker and more robust laminate than standard kits. The added density improves not just structural durability, but also thermal stability and the overall lifespan of your roof. The key differentiator, however, is the use of fire-retardant resins and topcoats, specifically formulated and tested to meet BS 476 Part 3 fire standards. This means the roof can help delay the spread of flame and reduce smoke generation in the event of a fire - offering peace of mind and compliance, all in one package.
A fire-rated kit is best suited to...
What’s Included?
Why Choose The 600g Fire-Rated Kit?
Whether you're a contractor working on a commercial project or a homeowner looking to improve your property, this kit ensures you're not just building for today, but protecting for the long term.