Shed Roof Felting, 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. You should aim to check the condition of your shed roof felt at least once a year. Doing this will allow you to spot potential problems early, rather than waiting until water starts to drip into the shed.
Depending on whether your shed is in a sheltered position or not, you might need to replace the roofing felt as often as every 2-3 years. However, buying good quality felt and doing a good job of fitting it should mean that maintenance will be required much less often.
Removing the Old Felt and 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. If any of the heads break off of the nails, hammer them below the surface of the wood so that there are no sharp points to rip the new felt. 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. If the timber planks are tongue and groove, you will need to cut through the tongue with a hammer and sharp chisel before you can lift the board out. Measure the existing timber planks and cut a new piece to match, either a new tongue and groove piece (cutting one of the tongues off) or a straight piece of softwood. Nail this in place using galvanised screws or nails, making sure that the heads are flush with or below the surface of the wood.
If there is damage to one of the fascia boards around the edge of the roof, or is one of them is missing, cut a new one from a matching piece of wood and paint it with wood preserver before nailing it in place. It is also a good idea to take the chance to treat the rest of the roof 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 length 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 the first side of the roof and nail it along the fascia at 50mm intervals. Smooth it out flat onto to the roof and nail along the top edge, spacing your galvanised nails at about 150mm. Smooth the felt over the sides of the shed and nail it into place.
Depending on how large the roof of your shed is, you may need to lay a second (or even third) strip of felt, overlapping the first, to take it up to just below the ridge (you need to finish about 50mm back from the ridge). To lay this second strip, overlap the first by about 50mm, making sure that the nail heads are covered by the overlap. Chalk a line along the edge of it and brush roofing felt adhesive onto this marked margin. Fix the second strip onto the felt adhesive, spread it out carefully over the roof and nail along the edges and top as you did for the first strip. Don’t nail through the overlap or you risk it not being waterproof. Press down firmly along the adhesive line to squeeze out any air bubbles. Repeat this for the other side of the roof.
Where the two pieces of felt meet near 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. If you need to cut it a bit wider than 200mm, do so. It is better to overlap too much than not enough.
Replacing Felt on a Flat Roof
If your shed has a pent roof (flat, with no ridge) you can apply the felt in exactly the same way as you would for one side of a pitched roof.
Start at the lowest edge and nail your felt along the facia. Spread the felt flat onto the roof and nail along the top edge of the felt. Spread adhesive along this top edge in a 50mm strip and apply the next strip of felt. The bottom edge of this second strip will sit in the 50mm of adhesive and the top should be nailed as before. Continue to do this until you reach the opposite edge of the flat roof.
Smooth the felt over the edge and nail in onto the fascia here. You can then go along the sides of the shed and nail the felt into the sides of the roof. Trim off any excess felt. 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.
SHED ROOF 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.
Roofing felt suitable for sheds is available in a number of colours, thicknesses and types. Most roof felt is bitumen coated and then finished with a coloured mineral (usually green or grey). The mineral finish both makes the felt more appealing and helps to stop the felt being damaged by UV rays. Better quality felt may by reinforced with polyester as well as bitumen and, depending on the location, could last for up to 15 years. However, you could find yourself paying two or three times as much for this type of felt.
Roofing Felt Adhesive
There are two main kinds of DIY roofing felt adhesive available, paint on and trowel on. Both are applied cold and do essentially the same job, but paint on adhesive is much easier to work with. For joining the sheets of felt on a shed roof, the paint on adhesive is perfectly acceptable (and generally much cheaper than the trowel on type).
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