I have to make penetrations in my roof for an attic fan and a vent cap for
a bathroom fan. The bathroom fan vent cap installation instructions
recommend using roof tar to put under the flashing and to seal the roofing
nails. The attic fan installation instructions recommend pure silicon
sealant for the same thing.
Any recommendations as to which I should use?
I would recommend using what they recommend. I doubt if either is going
to be a problem, but it is possible the materials used by each are different
and the use of the other product may damage those materials.
Are your flashings metal or plastic, if plastic most manufacturers
don't recommend that you use any kind of tar based sealer. For metal
if you have any nail heads showing it's a good idea to dab them with a
little tar. I agree that if you break the seal on the shingles around
your flashing a little dab of roof cement will stick them back down.
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