We are going to be reroofing part of our 1963 ranch with 4:12 roof. We’re taking it down to the rafters, sistering to the old rafters, and redecking. This is per: the engineer. We are also planning on covering the entire roof with an ice and water shield. This is common for flatter roofs where we live (7,500 in the Sierra Nevada).
My question has to do with which brand. My choices seem to be WR Grace ($94 for a 75′ roll at HD), Owens Corning Granulated ($59 for a 66.7′ roll at Lowes), and Owens Corning Mat (special order). I like to cost savings of the Owens Corning product, and it is 50 mil versus 40 mil, plus our roof is 64′ long so the lesser length is not a problem. But my concern is that the glue side may not stick to the granulated side as well as the Grace product.
The guy at the Lowe’s contractor desk says no problem, but I’d like other opinions. Also, does anyone know if the Mat product is similar to the Grace product re: top surface?
Thanks, Curtis
Replies
the glue will adhere to the granulated surface and the length makes no difference as you would just overlap the iceguard at the seams.
I guess my question would be why you feel the need to iceguard the whole roof? If everything is done properly felt will still have the chalk lines on it 50 years from now when you tearoff and reshingle.
Todd - Framing Square
being from ice dam land of Michigan and a roofer for 25 years Iwould tell why try to cut the cornors on price as if you have aproblem with the O.C. product the only recoruse is to replace it . somewhat costly after the shingle have put on. Grace is the only product that we recommend when doing repairs to correct ice dam problems. the granulated products don,t seem to seal the nail holes properly. They apply the granule to make ti more user friendly , which we think dosen,t add to sealing propertys. So why try to save a few bucks.
Thanks for the reply, Doc.
Yeah, we don't want to have to redo the underlayment - I've heard new ice and water shield does not stick to old real well - but there is some attraction to the thicker (and supposedly easier to handle) O.C. Product.
Are you familiar with the mat-faced product?
http://www.owenscorning.com/around/roofing/underlayment.asp
Cost is not a deal breaker, although the $210 savings on six rolls pays for most of the new framing nailer!
Not to go against local convention....but I'm still thinking a full deck ice shielded shouldn't be needed. Ice dams are due only partly to attic ventilation. For damming to occur.....heat's gotta be escaping somewhere. Maybe the local roofs are under-insulated also......or the houses poorly designed......as in hot can lights too close to the roof line.
That said....I have covered one whole deck with ice guard. The roof was a low pitch were shingle matching was very important. The Bld Inspector let me get away with 2.5/12.......as long as I ice guarded the whole thing.......which the shingle manufacturer said was OK...as long as extra venting was provided. I got enough with full soffit/ridge vent system.
So.....to make sure your shingles don't cook off the roof........better check to see what they require as the min venting.
I still say there's a weak link there somewhere......and/or a cold roof if that much snow sits would be the way to go. Jeff "That's like hypnotizing chickens........."
Thanks for the reply, Todd.
Covering the entire roof with ice and water shield is fairly common here. We will have several feet of snow on the roof for several months at a time. Our attic is well ventilated but is still warmer than the outside, so ice dams are a problem. Last winter was fairly mild, but I still had an ice dam well past the bearing wall.
Are you familiar with the Mat-faced O.C. product:
http://www.owenscorning.com/around/roofing/underlayment.asp
Doc's comments about the granulated product not sealing nails concerns me. What is the purpose of the granulation when the packaging recommends not walking on it anyway?