Roof felt, otherwise known tar paper, is a heavy grade paper that is made from tar-impregnating paper, thereby producing a waterproof material that is used as a moisture barrier in roofing. Roof felt lies between the roof decking and the roof barrier and is implemented as an added layer of protection from rain, ice, and snow. Typically sold in 36” wide rolls, roof felt is essentially an underlayment to the barrier protection of your roofing system.
Why is roof felt needed?
Roof felt protects the roof and provides a barrier between the roof decking and the final roofing material. Should water or snow be driven between shingles by high winds, this underlayment will provide additional protection from any leaks. When roof felt is used during a roof replacement, the roof deck is protected in the event that it rains before the roof is completed. Roof felt also protects the roof should any shingles be blown away in a storm.(See Illustration Below) Most importantly, many municipalities require roof felt as part of their building code, not to mention that most shingle manufacturers require the installation of roof felt for proper warranty coverage.