On 4/1/2011 8:08 PM Joe spake thus:

On Apr 1, 10:54 pm, (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?

Asphalt felt is no longer considered for anything but the cheapest
roofing work. In our area, the popular replacement is one of the newer
plastic sheeting types, like Permafelt. It is a far better second line
of defense against unexpected shingle failure and can be left on the
sheathing for some time while waiting on a roofing crew. Additionally,
it is safer to walk on while installing the shingles.

So to answer the OP's question: what *is* the function of underlayment?
Is it a backup in case of shingle failure? or something else?


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