Q: Why is felt paper used in roofing?
—Bill, Pleasant Hill, Miss.
A: Tom Silva replies: Felt paper is typically used in most roofing as a release between the two materials, wood and asphalt. Years ago, it was used on roofs because when sap would come out of the wood, it would break down the "backside" of the asphalt shingles and cause them to deteriorate, which isn't a problem anymore. But I also think of it as a lightweight protection against any damage on a stormy day. Let's say a shingle or a tile should break in a storm. If the roof has a layer of felt paper over it, it has got some protection that will resist the driving rain at least for a little while. But you need a different weight of felt depending on the type of roofing product you're using.