"Tom" wrote in message
Sounds like you work for W.R.Grace, a major supplier of bituminous
membrane.
Being from Michigan, I'm _very_ familiar with ice dams, and with the
latest and
greatest of ice and water shield technology. A double coverage of 30 lb.
felt
installed up only 3 feet beyond the inside wall will stop an ice dam from
penetrating the decking perfectly well, and cost less than the modified
bitumin

Grace is garbage, being familiar with the latest technology you should know
this and not bring that name into the subject. You are 100% wrong in
assuming double coverage felt will stop ice from creeping under it. That
statement is laughable even by those that don't know much about roofing,
those with a little common sense would even know that. I take it you're one
of those weekend warriors, since your knowledge is lacking.



I suggest you look at a shingle to see if there even IS a tar strip on the
backside. Felt is laid just for the reasons I stated. Hope this helps. Tom

I suggest you look what is holding the cellophane on the back of shingles,
guess what that substance is? And yes the tar strip melts when heated, and
creeps from under the cellophane, which in turn sticks to the felt or roof
deck if felt is lacking.

If you need any knowledge you want to pass on, so you don't look like such a
fool. Just ask and you shall receive. No charge for roofing 101 course
today.