On 2 Apr 2011 03:54:39 GMT, (Micheal C.
Jordan) wrote:


Shingles (standard three tab type) have felt (tar paper?) installed on the
roof first, and then the shingles are installed. What is the function of
the felt? I understand there are 2 types of felt, perforated and
non-perforated. Is perforated felt for vapour movement? What happens if
the felt is not installed?



Generally speaking, if the felt is not installed the guarantee is
void. The felt seals the roof. Perforated lets vapour out without
letting water in. The shingles protect the felt and flow the water off
the roof, but the felt repels any water that gets through or blown
under the shingles, and directs it downstream rather than letting it
penetrate the roof.

There were a lot of roofing contractors in these parts installing the
newer fiberglass shingles without felt a few years ago, trying to be
price competetive - virtually all have now gone back to using felt
because their failure/callback rate was too high without.

In fact quite a few premium roofers are now using the"blue-seal" type
membrane used as ice-guard over the entire roof. That stuff sticks
like snott, and seals around the nail holes, making a totally
leakproof seal.