Fibreglass, or GRP (glass-reinforced plastic), roofing has grown in popularity over the last two decades thanks to its impressive durability, watertight properties, and relatively low maintenance. However, like any roofing material, it’s not immune to wear and tear. Over time, exposure to the elements, improper installation, or simple ageing can lead to problems that compromise a roof’s integrity.
The good news is that many fibreglass roof issues are easily repairable if caught early. In fact, most can be addressed quickly using the right tools and materials, saving homeowners from the expense of a full roof replacement. Below, we explore five of the most common GRP roofing problems and how to fix them using practical, cost-effective methods such as general fibreglass repair kits.
1. Cracking or Crazing on the Roof Surface
Over time, exposure to UV rays and fluctuating temperatures can cause fibreglass roofs to develop hairline cracks or a network of fine lines known as “crazing.” These may seem minor at first but can quickly escalate into deeper fissures that allow water ingress if left untreated.
Solution:
The key is to catch surface cracks early and seal them before they spread. A general repair kit containing resin, fibreglass matting, and a catalyst provides everything needed for a seamless fix. After lightly sanding the damaged area, apply a fresh layer of fibreglass and resin to reinforce the surface. Once cured, a topcoat can be added to restore waterproofing and UV protection.
2. Leaks Around Roof Edges or Joints
Although GRP roofs are seamless when installed correctly, leaks can still occur—particularly around edges, trims, or areas where flashing meets the roof surface. These junctions are more susceptible to thermal movement, leading to separation or weakness over time.
Solution:
First, identify the exact source of the leak, which is often located near overlaps, corners, or terminations. After cleaning and roughing the surface, apply a repair patch using chopped strand matting and resin, overlapping slightly beyond the affected area. General repair kits are especially useful here, offering a ready-made solution with precise quantities for small to medium repairs.
3. Delamination (Peeling Layers)
Delamination happens when the topcoat begins to separate from the resin layer below. This issue is commonly caused by moisture trapped during application, poor bonding due to dust or oil, or ageing. It not only affects the roof’s appearance but also undermines its waterproofing properties.
Solution:
Begin by removing any loose or flaking material. The area should then be sanded and thoroughly cleaned. Once prepped, use a repair kit to reapply fibreglass layers and reseal the surface. In most cases, adding a new layer of topcoat after the resin cures is sufficient to restore the roof’s protection.
4. Ponding Water
Flat fibreglass roofs should be installed with a slight fall to allow water to run off efficiently. However, over time or due to poor design, some roofs develop low points where water accumulates, a phenomenon known as ponding. While fibreglass is inherently waterproof, prolonged exposure to standing water can lead to degradation.
Solution:
If possible, adjust drainage or add tapered insulation to encourage runoff. For smaller dips, the roof can be built up locally using layers of fibreglass and resin to create a more even gradient. A general fibreglass repair kit is ideal for filling in these slight depressions, reinforcing the area and preventing future ponding.
5. Surface Blistering or Bubbles
Blistering on a GRP roof often results from moisture or air becoming trapped under the topcoat during application. These raised areas can expand under heat, potentially breaking open and exposing the underlying material. If untreated, blisters compromise waterproofing and invite further issues like cracking and delamination.
Solution:
Blisters should be punctured and removed to expose the raw surface. Once the compromised material is eliminated, sand the area and prepare it for repair. Applying new matting and resin ensures that the affected spot is sealed correctly. Follow this with a fresh topcoat for optimal protection and finish.
Prevention: The Best Fix is Early Intervention
While GRP roofs are renowned for their longevity, often lasting 20 years or more, their performance hinges on proper maintenance and timely repairs. Regular inspections, particularly after extreme weather, can reveal minor problems before they evolve into major ones.
Repairing small issues with a high-quality fibreglass repair kit is far more cost-effective than replacing large sections of the roof. Whether you’re a seasoned roofer or a hands-on homeowner, keeping a kit on hand can make a significant difference in your roof’s lifespan.
Choosing the Right Materials
Not all repair kits are created equal. For effective results, it’s essential to use components designed specifically for GRP roofing. Kits should include pre-measured quantities of resin, catalyst (hardener), fibreglass matting, and tools for mixing and application.
Using low-grade products or mismatched materials may lead to adhesion problems or weak spots, so sourcing from trusted suppliers is important. Apex Fibreglass Roofing Supplies offers a range of specialised kits tailored to different project sizes, ensuring consistency and reliability across repairs.
Fix It Fast: How to Repair Common Fibreglass Roof Problems
Fibreglass roofs offer exceptional durability, but they’re not immune to damage. The good news is that most common problems, cracking, leaks, delamination, ponding, and blistering, can be swiftly and effectively addressed using a general fibreglass repair kit.
Timely intervention not only prevents further deterioration but also helps maintain the performance and value of your property. With the right approach and quality materials, even a DIY enthusiast can restore a GRP roof to peak condition.
After all, protecting what’s above your head starts with paying attention to what’s under your feet.