Replacing worn and split felt on the roof of a shed is essential if you want your tools and other garden equipment to stay in good condition. Depending on whether your shed is in a sheltered position or not, you might need to replace the felt as often as every 2-3 years.
Removing the nails
The first thing you need to do is remove the old, worn felt from the roof. Generally the felt is tacked all the way along each edge. Locate and pry loose all of the nails using a small pry bar or a claw hammer. It is a good idea to wear goggles and safety gloves while doing this as old felt can throw off a lot of small bits of grit as it is moved around. With all of the nails removed you can strip the old felt off the roof.
Check the timber
Have a good look at the exposed timber (especially where there were holes in the felt) and make sure that it is sound. If any of the timber needs to be replaced, do so now. Measure the existing timber planks and cut a new piece to match. It is also a good idea to take the chance to treat the timber with a coat of wood preserver. Let this dry completely before continuing.
Laying the new felt (ridged roof)
Unroll your new sheet of felt and measure out the size of the roof. Rolls of felt are not often available as wide as a shed roof, so you will need to cut more than one pice to cover the whole roof. Make sure that any section of felt you cut has about 50mm extra on each edge to allow the joints to be sealed well. You can cut felt easily enough with a stanley knife and a straight-edge.
Cut one piece for one side of the roof and nail it along the ridge first. Then repeat for the other side of the roof. Where the felt reaches the sides and bottom of the roof, nail it into the edge of the planks, not the face, using galvanised clout nails.
Where the two pieces of felt meet at the ridge, cut a strip of felt the length of the roof and about 200mm wide. Spread strong, waterproof mastic sealer on the underside of the felt strip and also a little along the nail lines at the ridge. Now use this strip to "cap" the ridge, pressing it down firmly and evenly. This strip should completely cover the nails.
Flat roof
If your shed has a flat roof, each strip of felt should be overlapped and then nailed along the overlap. Cut strips of felt wide enough to cover the overlap and the nail line and cover the underside with mastic sealer. Stick these strips down over the joints to seal them. The edges should be nailed in the same way as a ridged roof, i.e. into the edges of the wood rather than the face.
Safety
Shed roofs may not be particularly strong so work from a stepladder or platform at the side of the roof. If you need to move onto the roof of the shed, use planks to spread your weight across the roof.
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