Types of Fibreglass Roofing Systems

1. Polyester Based GRP Roofing Systems

Traditional polyester-based fibreglass roofing systems like Fibrelast, also known as GRP roofing is the OG of this type of system and has been a part of the UK market since the mid-20th century, gaining popularity in the 1970s for its durability and weather resistance, particularly for flat roofs. The system consists of three main components: polyester resin, fibreglass reinforcement of either 1 or 2 layers of 450g or 1 layer of 600g chopped strand matting, and a polyester topcoat with some type of activator or catalyst to activate the curing.

GRP Roofing is known for its exceptional durability, often lasting 20-30 years with proper installation and it's resistance to weathering, UV radiation, and physical damage makes it a reliable choice. One of its key benefits is its seamless, joint-free surface, which eliminates the risk of leaks commonly associated with other roofing systems. This makes GRP particularly suitable for flat roofs, balconies, and walkways. It is also a low-maintenance option, requiring only periodic cleaning and inspections to ensure its performance remains optimal.

In addition to its practicality, GRP roofing is highly versatile and adaptable to various roof shapes and designs, including complex structures with curves and angles. It can be used on both flat and pitched roofs. Furthermore, it offers aesthetic appeal, Our Fibrelast system is available in five different colours as standard with more on request that can be tailored to complement the building’s appearance, providing a modern and sleek look. GRP roofing is fire-resistant, adding an extra layer of safety to the property, and many systems are now designed with sustainability in mind, using solvent-free resins and recyclable materials to minimise environmental impact.

Despite its many advantages, GRP roofing has some drawbacks. If you were to hire a professional contractor the initial cost of installation can be higher than that of other roofing materials such as felt. Installation is also sensitive to weather conditions, as GRP roofs need specific temperatures to cure effectively. Extreme weather, such as cold or wet conditions, can compromise the integrity of the roof during the installation process.

Additionally, this type of GRP Roofing system can only be applied onto suitable substrates, such as OSB (Oriented Strand Board) or marine-grade plywood. It cannot be overlaid onto existing roofing surfaces, which means stripping back and applying new decking, installation etc. It's also worth noting that polyester resin systems are made for strength rather than flexibility and although modern-day GRP roofing systems have been adapted to be slightly more flexible expansion joints could be required on flat roofs over 50m².

Another consideration is the environmental impact of polyester based resin systems, which can contain high levels of VOCs, including Styrene which gives them increased odour content necessitating proper planning measures during installation.

2. Polyester Overlay GRP Roofing Systems

While very similar and even marketed as a GRP Roofing system, these hybrid polyester systems were made by manufacturers to be applied over existing roof surfaces with the use of a primer. Unlike the traditional GRP roofing above, these systems will typically use one resin for both the base layer and topcoat, while the type of fibreglass matting will usually be reduced to 225g or 300g.

While most of the positives remain from the traditional GRP roofing the hybrid polyester system still requires expansion trims for roofs over 50m² and still has high VOCs including styrene. The main issue however is if your roof needs a repair. With a traditional GRP Roofing system if you had a crack or pinholes in the roof surface you could easily sand back the repair area using a repair kit for very little cost. With these polyester overlay systems, you need to apply the entire system again which would increase costs.

3. PET-based fibreglass roofing systems

PET-based fibreglass roofing systems or "Sustainable GRP Roofing Systems" as they are marketed  incorporate resins made from Polyethylene Terephthalate (PET), a type of plastic commonly used in everyday items like water bottles, food packaging, and textiles. PET is lightweight, strong, and recyclable, making it an attractive choice for environmentally-conscious applications. By using recycled PET in the resin formulation, these roofing systems help reduce plastic waste and promote sustainability by giving new life to discarded materials.

While the use of recycled PET resin in GRP roofing systems is an innovative and eco-friendly advancement, there are notable limitations. The system as a whole still relies heavily on traditional polyester-based resins, meaning only the bases layer of the system will only benefit from the sustainable properties of PET, the rest of the system is still based on the traditional polyester based resins from above.

Another drawback is the continued presence of high levels of volatile organic compounds (VOCs) including Styrene during installation. These emissions pose risks to both installers and the environment, requiring adequate safety measures to mitigate their effects. Due to the high levels of VOCs, this system is unsuitable for use in sensitive environments such as schools and hospitals and office buildings where these types of systems would be most valued for their envorionmental benefits.

4. PU based fibreglass roofing systems

PU-based fibreglass roofing systems like Fibrecoat offer a modern and advanced alternative to the polyester-based fibreglass roofing systems above, with several key advantages. Unlike polyester systems, PU systems simplify the application process as they do not require a catalyst or a separate topcoat, reducing installation time and minimising the risk of application errors. This streamlined approach makes Fibrecoat more accessible and ensures greater consistency in results.

In terms of performance, Fibrecoat excels in durability and flexibility, adapting better to thermal expansion and contraction, eliminating the need for expansion joints. Additionally, PU systems have low VOC emissions and are free from Styrene, making them a safer and more environmentally friendly choice, particularly for sensitive environments like schools and hospitals.

Just like the polyester-based overlay systems above, Fibrecoat can also be applied not only to new roofs but directly over existing roof surfaces such as felt, concrete, EPDM, and bitumen. This adaptability reduces the need for costly roof removal and disposal, saving time and money while providing a seamless finish.

While they come with higher initial costs than polyester-based fibreglass systems, their long-term benefits make them a preferred option for high-performance applications. Traditional polyester systems may still be a viable choice for projects with tight budgets or less demanding performance requirements, but they lack the versatility and advanced features of systems like Fibrecoat.

Comparing the different systems

Selecting the best fibreglass roofing system for your project involves careful consideration of several factors. Start by evaluating your budget, as different systems come with varying costs. Consider the type of building and its specific requirements.