Lound banging noises

A common concern with fibreglass roofs, particularly at night, is loud banging or popping noises. These sounds are typically caused by thermal expansion and contraction of the roof structure. As temperatures drop in the evening, the materials cool and contract, causing stress within the roof system. Without proper allowances for this movement, such as expansion joints, the fibreglass can flex or shift abruptly, creating the noises reported.

In the video below you can hear the roof cracking and banging as the roof contracts from a warm day. The owner notes that the roof is over 50m² and wasn't installed with any expansion joints.

All of the GRP Roofing systems on the market today are made using polyester resins and topcoats which are incredibly strong but not very flexible. Over the years systems like Fibrelast have been engineered to be more flexible but there is a limit on just how flexible you can make a polyester resin system.

This is why If your flat roof's surface area is over 50m² in size and there's nothing else on the roof (windows or lanterns) to break up the space then you need to install expansion joints or consider switching to a system like Fibrecoat that has incredible flexibility and can be applied without the need of these trims.

If you have an existing GRP roof and are suffering from these banging and creaking noises we would suggest speaking to your original contractor or getting a site visit from a local fibreglass roofing specialist. They would be able to assess the roof and pinpoint the cause of the noise. We have written an article called Noises Coming From my GRP Roof with more information on the issues and some possible solutions.

Fibreglass Roof Cracks

Cracks in GRP Fibreglass roofs can result from various factors, often related to installation practices and environmental stresses. Improper installation, such as applying the topcoat too thickly or before the laminate has fully cured, can weaken the roof. These mistakes prevent proper bonding and flexibility, making the roof more susceptible to cracking over time.

Other contributing factors include the use of inadequate decking materials, such as plywood or chipboard, instead of more durable options like OSB3 boards. Poor quality decking can lead to delamination and cracking, especially under stress. Environmental exposure also plays a role, weathering can degrade fibreglass over a long period of time, causing it to become brittle. This ageing process often results in ‘alligatoring,’ where the roof surface develops a wrinkled and cracked appearance.

Fixing cracks in a fibreglass roof involves several key steps to restore its integrity and prevent further damage. Begin by thoroughly cleaning the affected area to remove dirt, grease, and debris. Once clean and dry, sand the cracked area lightly to roughen the surface, ensuring better adhesion for the repair materials. For smaller cracks, a GRP roofing repair kit containing resin and fibreglass matting can be used. Apply a layer of resin over the prepared area, lay the fibreglass matting on top, and saturate it with more resin. Smooth out any air bubbles and allow the resin to cure completely. For more extensive cracks, it may be necessary to cut out the damaged section and replace it with new fibreglass layers. Once the repair is complete, apply a fresh topcoat to seal the area and provide UV protection.

Pinholes

Pinholes on a GRP fibreglass roof are small holes that can compromise the waterproofing and integrity of the roof. They often occur when the fibreglass matting is not fully saturated with resin during installation, leaving tiny air pockets that manifest as surface defects. Another common cause is applying the topcoat too quickly or over laminate that has not fully cured, which can result in incomplete bonding and the formation of pinholes. Although these imperfections may seem minor, they can allow water ingress, especially during heavy rainfall, potentially leading to leaks and further damage over time.

To repair these pinholes, start by thoroughly cleaning the affected area to remove dirt, debris, and grease. Once the surface is dry, lightly sand around the pinholes to create a rough surface for better adhesion. Apply a fresh layer of topcoat, ensuring it penetrates and fills the pinholes. Proper application is crucial to prevent the recurrence of pinholes.

Ageing and Environmental Exposure

A well-laid fibreglass roof will last well over 20 years but over time they can experience ageing a degradation due to prolonged environmental exposure. Factors such as UV degredation, extreme temperatures and harsh weather will over time lead to discolouration and general wear and tear as you can see from the image below which was taken from an 18-year-old GRP roof on top of a train station for a steam railway line.

Over the years the dirt and smoke from the steam trains along with the weather had hit this roof hard and although it wasn't leaking it needed a refresh. With this particular roof, the contractor cleaned the roof thoroughly and applied two layers of the Overcoat Roofing System directly to the GRP roof layer.

To refresh an ageing GRP flat roof using Overcoat, you need to begin by thoroughly cleaning the roof to remove debris, algae, and dirt that may have accumulated over time. Inspect the surface for signs of damage, such as cracks, blisters, or delamination. These can be repaired either by sanding the surface to remove degraded material and create a clean bonding area or by applying a layer of Sharkseal into any cracks leaving it overnight to cure.

Once repairs are complete, you can apply up to two layers of the Overcoat system directly to the roof surface, starting with any joints or details first and then applying over the main surface area. Once cured the system will provide a strong, flexible membrane over the existing roof that will refresh the look of the roof and protect it for many years to come.

While GRP fibreglass roofing is renowned for its durability and versatility, cracks and splits can compromise its performance if not addressed promptly. Understanding the common causes, from thermal expansion to poor installation, allows for proactive measures to minimise risks. Timely repairs are essential to preserving the integrity and longevity of the roof. By investing in quality materials and adopting preventive practices, homeowners and businesses can ensure their GRP roofing remains a reliable, long-term solution for protecting their properties.