Felt paper is needed to protect the plywood used to build the roof surface for most outdoor backyard sheds. The felt absorbs moisture that rises up in the shed and through the roof. Moisture will cause wood rot and lead to leaks. Eventually, you'll have to replace the entire roof if the condition gets really bad. Whenever you are putting down a new roof on your shed, you'll also need to lay down a layer of felt over the plywood to protect against moisture damage. If you are doing the roof work by yourself at home, here is how you would apply a layer of felt paper to protect the plywood used to build the roof.
Whenever you are tearing off old worn shingles so you can put on new ones, you also should remove all of the old felt paper and nails. The best thing to use is a long-handled roofing scrapper.
You will be able to see the plywood used to build the roof once the felt paper has been removed. Check for any moisture damage and rotting. If you find wood that is rotting, you need to replace it before you cover it with a new layer of felt paper. You also want to make sure the wood is completely dry before you put down the felt paper to avoid trapping moisture between the wood and paper.
Set Chalk Lines
You should put chalk lines across the roof to help you keep the felt paper straight. You start by measuring the width of the felt paper you are using (sizes vary) on one side of the roof. If the width is 36 inches, you want to measure 36 inches from the edge of the roof up toward the peak and place a mark on the roof surface. Now, go to the other side of the roof and do the same thing. Stretch the chalk line out so it touches each mark and snap the line with your fingers. A straight chalk line across the roof will appear.
Installing Felt Paper
The felt paper comes in rolls. Take the felt paper and roll it out over the roof. Start at one side and roll it all the way across to the other side. You should have a couple of bricks or rocks handy to place on the paper as you unroll it. This will keep the wind from blowing the felt paper around while you are unrolling it. Roll the paper all the way to the other side of the roof and cut it so it drapes over the other edge a little bit. Line the top of the felt paper up to the chalk line and nail or staple it in place. You also want to nail or staple it down along the bottom edge of the roof, too. The nails or staples should be spaced about three or four inches apart from each other.
You now need to set another chalk line. You want the felt paper rows to overlap one another so any moisture will drain off of the roof without touching the wood. The second row should overlap the first one by a couple of inches. If you are using 36" wide felt paper, you'll want to measure 32" or so from the top of the first row and make a mark on the roof. You then do the same thing on the other side of the roof. Snap a new chalk line and install the second row the same way you did the first row. Keep on repeating this process until you reach the peak of the roof.
Trim the excess felt paper along the side edge of the roof to make it flush with the roof's surface. You are now ready to start applying the shingles. For more information, contact local professionals like JSI Roofing.