How to prepare your roof for fibreglass flat roofing application?

Fibreglass flat roofing, known for its durability and longevity, is a popular choice for homeowners and commercial property owners alike. However, the success of a fibreglass roof installation largely depends on the preparation work carried out beforehand. Proper preparation ensures that the fibreglass adheres well and provides a waterproof, long-lasting surface. Here’s a comprehensive guide on how to prepare your roof for a fibreglass flat roofing application.

1. Inspect the Existing Roof

The first step in preparing your roof for fibreglass application is a thorough inspection of the existing roof structure. Look for signs of damage, such as leaks, rot, or structural weaknesses. Ensure that the roof deck is solid and free from any moisture or decay. Any compromised areas must be repaired or replaced to provide a stable base for the fibreglass.

2. Remove Existing Roofing Material

If the current roofing material is in poor condition or incompatible with fibreglass, it needs to be removed. Stripping off old materials such as felt, asphalt, or EPDM is essential to ensure the new fibreglass layer adheres properly. This step might involve scraping, pulling nails, and cleaning up any debris. The roof deck should be left clean and smooth.

3. Ensure a Dry Surface

Moisture is the enemy of fibreglass roofing. Before proceeding with the application, make sure the roof deck is completely dry. Any trapped moisture can cause problems down the line, such as blistering or delamination. If there has been recent rain, allow sufficient time for the deck to dry out. Using a moisture meter can help confirm that the deck is ready.

4. Repair and Reinforce the Roof Deck

Examine the roof deck for any signs of wear or weakness. Replace any damaged sections with new plywood or oriented strand board (OSB). Secure loose boards with screws or nails, ensuring the entire deck is firm and even. Pay special attention to the edges and corners, as these areas often require additional reinforcement. For large roofs, it may be necessary to install extra joists or beams to support the new fibreglass layer.

5. Install Edge Trims and Upstands

Proper edge detailing is crucial for the longevity of a fibreglass roof. Install pre-formed edge trims around the perimeter of the roof. These trims not only provide a neat finish but also prevent water from seeping under the fibreglass layer. For areas where the roof meets walls or other structures, install upstands to ensure a watertight seal. These should be securely fixed and sealed to the existing structure.

6. Apply a Suitable Primer

Priming the roof deck is a critical step that promotes the adhesion of the fibreglass to the substrate. Use a primer that is compatible with both the fibreglass and the type of deck material you have. Apply the primer evenly across the entire surface, ensuring complete coverage. Allow it to dry thoroughly according to the manufacturer’s instructions before proceeding.

7. Prepare the Fibreglass Materials

Before starting the application, gather all necessary materials. This includes fibreglass matting, resin, hardener, and any tools required for mixing and applying the materials. Cut the fibreglass matting to size, ensuring it fits well over the roof surface with minimal overlaps. Having everything prepared and within reach will make the application process smoother and more efficient.

8. Mix and Apply the Resin

Follow the manufacturer’s instructions to mix the resin and hardener correctly. It’s important to mix only as much resin as you can use within the working time, as it will start to set quickly. Apply the mixed resin to the roof deck using a roller, working in manageable sections. Ensure an even coat that thoroughly saturates the fibreglass matting.

9. Lay the Fibreglass Matting

Once the resin is applied, lay the pre-cut fibreglass matting onto the wet resin. Use a roller to press the matting into the resin, eliminating any air bubbles and ensuring full adhesion. Overlap joints by about 50mm, applying extra resin if necessary to bond the layers securely. Continue this process until the entire roof is covered.

10. Apply Additional Resin Layers

After the initial layer of fibreglass matting is in place, apply additional layers of resin as required. Typically, two to three layers are needed to achieve the desired thickness and strength. Allow each layer to cure before applying the next, ensuring a robust and durable finish.

11. Sand and Finish the Surface

Once the final layer of resin has cured, lightly sand the surface to remove any rough edges or imperfections. Clean off any dust or debris before applying a topcoat. The topcoat provides additional UV protection and enhances the waterproof properties of the fibreglass roof. Apply it evenly and allow it to cure thoroughly.

12. Inspect and Maintain

After the installation is complete, inspect the roof to ensure there are no missed spots or imperfections. Regular maintenance checks are essential to keep the fibreglass roof in optimal condition. Remove any debris, check for signs of wear or damage, and address any issues promptly to prolong the life of the roof.

By following these steps, you can ensure that your roof is properly prepared for a fibreglass flat roofing application. Taking the time to do thorough preparation will result in a durable, waterproof roof that provides long-lasting protection for your property.

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