Repairing a Felt Roof

It is quite easy to repair bubbles or blisters in a felt roof with a few simple tools and some bitumen (available from all good DIY stores). Blisters or bubbles are caused when water penetrates the felt through a crack or hole and then expands with the heat and lifts the felt away from the roof.

First you need to make two cuts in a X shape through the blister. Peel back the four triangles the cuts have made (use a hot air gun to warm the felt if it is stiff) and let the timber beneath dry for a while. Now liberally coat the area under the cuts with Bitumen adhesive and leave it to become tacky to your touch. When it is, press down the triangles of felt firmly into the bitumen. You can use galvanised nails to hold the points of the triangles down if they refuse to sit flat.

You now need to apply another liberal coat of bitumen all over the cuts. If you have spare roofing felt, cut a square around 100mm bigger than the cuts and lay this into the tacky adhesive. Seal the edges of this with more bitumen and sprinkle the wet bitumen with small solar reflective chippings.