Start with a clean, sound roof deck and work from the lower edge of the roof upwards so each higher strip overlaps the one below. The exact lap and fixing spacing depends on the felt being installed, so check its instructions before cutting.
1. Remove the old felt and every loose fixing
Strip back damaged felt, pull out old nails and clean the roof. Replace rotten, badly swollen or broken OSB or plywood before covering it. New felt will not repair a failed roof deck.
2. Measure both roof slopes before cutting
Our Mineral Shed Roofing Felt is a 10m × 1m roll, giving 10m² gross area before overlaps, edge returns and waste. Measure the actual roof rather than the shed footprint.
3. Lay the lowest strip first
Position the felt along the eaves with enough material for the specified edge detail. On a pitched shed roof, later strips should overlap the lower strips so water sheds over the joints rather than into them.
4. Use roofing felt nails where the system requires mechanical fixing
Use galvanised roofing felt nails rather than small ordinary nails. Choose a nail length that suits the roof deck and check that unnecessarily long points will not project into the shed.
5. Bond laps and edges where the felt system calls for adhesive
Black Jack 904 Roof Felt Adhesive is designed for compatible bituminous felt and sealing felt laps. Do not assume every roofing felt uses the same adhesive pattern; follow the felt instructions.
6. Finish the ridge and edges before calling it done
Secure the ridge and perimeter using the detail specified for the shed and felt. Barge boards or timber trims can protect exposed edges as well as giving a cleaner finish.
If the existing felt only has local damage, see How to Repair Shed Roof Felt before stripping the whole roof.
