How to Felt a Flat Roof

Tips and Tricks to Felting a Flat Roof

Felting a flat roof is an effective way to create a waterproof and durable surface that protects against the elements. Roof felt is a popular choice due to its affordability, ease of installation, and weather resistance. Whether covering a new roof or replacing old felt, the process requires careful preparation and correct layering to ensure a long-lasting finish.

The first step in felting a flat roof is preparing the surface. The roof decking should be clean, dry, and free from any debris. If replacing old felt, remove any damaged material and inspect the wooden deck for signs of rot or weakness. Any necessary repairs should be carried out before applying the new felt to prevent future issues. A layer of underlay or primer can be applied to improve adhesion and protect the wood beneath.

Next, the first layer of roofing felt is laid down. This is typically nailed or tacked onto the decking, starting from one edge and working across the roof. The felt should overlap at the edges by around 50mm to ensure a watertight seal. The first layer acts as a base to provide stability and additional protection for the top layers. It is important to ensure the felt is flat and smooth, with no bubbles or wrinkles that could lead to weaknesses over time.

Once the base layer is secure, the second and third layers are applied using either a torch-on method or cold adhesive. Torch-on felt is heated with a gas torch to bond the layers together, creating a seamless and waterproof finish. Cold adhesive is an alternative method where a special glue is spread over the felt before rolling out the next layer. Both techniques require careful application to avoid air pockets and ensure full adhesion.

The edges and joints of the felt must be properly sealed to prevent water ingress. A protective mineral layer or solar reflective paint can be applied to the final layer to extend its lifespan and protect against UV damage. If the roof has any protrusions such as vents or chimneys, special attention should be given to sealing around these areas to prevent leaks.

Regular maintenance can help prolong the life of a felt roof. Checking for cracks, tears, or lifting seams allows for early repairs before major damage occurs. Keeping the surface free from debris and ensuring good drainage can also prevent water from pooling and causing premature wear.

In conclusion, felting a flat roof involves surface preparation, layering felt correctly, sealing joints, and applying a protective finish. Whether using a torch-on or adhesive method, careful application ensures a strong and waterproof roof that can withstand the elements for many years.