Roofing cement

I’m finishing up the hole in my roof tomorrow. I found that the flashing had a gash in it and was letting water in for years and rotted through the roofing felt and finally the sheathing in the bottom corner of the roof. I pulled up the the shingles and replaced a 1’x2’ piece of sheathing already. The only thing I have left to do is put down new roofing felt and replace the shingles which the roofer left extras of. I’m confused about one thing. I’m sliding a new piece of felt under the old and was adviced to use blackjack neoprene flash cement in between the vertical overlap of the roofing felt, and to hold down the shingle tabs on the starter strip but the blackjack instructions state not to use it in between felt or on shingle tabs. It doesn’t state why. I heard roofers use this stuff for that exact purpose all the time. Anyone know why?? Does it have anything to do with it being so flammable?? Could it eat away at the felt??

there should be no need for it.


You need to use a thin layer of cement. We hand seal shingles with roof cement.

We use to make ice shield with mastic and felt.

ditto aaron,when using tar under shingles(usually a mansard style),they recommend quarter size dollops at most–excess amt.s will cause blistering ,and loss of granulation

oh god.
thats what comes to mind when i read that question.
mr/ms farrington,
you dont know much bout roofin do ya?

first thing is you need to concern yourself with gettin your shingles reinstalled properly and not whats goin on underneath them.

if it makes ya feel better by squirtin somethin inbetween the felt laps,
so you can get it all over yourself, then by all means squirt away. squirt extra in there.

heres a thought for ya.
if ya did not have felt under your shingles, you wood have seen leak
4yrs ago, and would have been able to fix with a little dab a caulk.
wouldnt be doin all this wood work now.

but you go on ahead and worry yourself about your felt paper.

eya later.