I’ve got a existing roof that the HO’s wish to add additional insulation. <!—-><!—-><!—->
The existing shingles will be torn off, exposing 1 1/2″ polystyrene board <!—-><!—->
which is nailed thru to the 2×6 T&G sheathing (exposed to interior) with 3″ roofing nails.<!—-><!—->
This is a low budget re-roof, and am looking for like suggestions on<!—-><!—->
adding additional insulation (thinking 1″ more rigid polystyrene).<!—-> <!—->
I’m thinking of: <!—-><!—->
– tear off existing shingles<!—-><!—->
– add 2″ new polystyrene on top of exisiting<!—-><!—->
– add new 7/16″ osb<!—-><!—->
– new composition shingles<!—-><!—->
The new sheathing will be nailed thru the insulation into the 2×6 T&G. Longer nails<!—-><!—->
thru to the existing log rafters. The shingle manufacturer may void their warranty on<!—-><!—->
this installation, may or may not have to convince the inspector of the credibility of<!—-><!—->
this installation. I’m not convinced that ventalating this roof (shingles) is necessary,<!—-><!—->
and will be built as a cold roof. <!—-><!—->
Replies
House photo forgot to add!
I'm bumping up this thread in hopes of a few responses?
This doesn't sound all that low-budget. How are you going to ventilate it with the insulation there, if its a cold roof?
They make panels for what you are trying to do (foam+osb): atlasroofing.com
I guess I should rephrase "low budget" to least expense. Thanks for responding. Your right on with the hot roof, the air gap wasn't shown on the detail, but am wondering if it's worth venting at all. I realize the shingle warranty will most likely be void, and I may not be able to convince the inspector. Trouble is, I can't build up the profile of the roof much more than 2", so I think the panels are out. Thanks again.
I believe Certainteed allows hot roofs in their waranties. Maybe Elk too. GAF doesn't seem to as far as I can read it.
Yeah, except the Certainteed warranty isn't worth excrement.--------------
No electrons were harmed in the making of this post.
Must be a regional thing, 'cause Certainteed bends over backwards for me. I had a missmatch problem this spring. They told me to fix it and send them a bill. I did and they rounded it up to the next thousand dollar mark. When was the last time you got paid several hundred bucks more than your bill?Birth, school, work, death.....................
They paid a little over $600 on a $5300 job. Their "25-year" shingles lasted 9 years. They say the shingles weren't defective.The previous "spec home" shingles lasted 19 years.
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No electrons were harmed in the making of this post.
Well, we found a insulated 1 1/2" foam board product used for flat roofs we will be using over the existing foam board. All of the existing shingles are off, and miriculously it all survived the tear-off. The new board claims to be R-8, so that will most definately help without altering the existing profile too much. The new board will go down directly on the old, with 1x furring over, then new 7/16" osb which will allow a 3/4" air space for ventilation. The new facias will be a vented drip edge, and we’ll put new ridge vents in. So, no issues with shingle warranty per my roofing supplier.
Thanks for all the usefull info., I did like the atlas roofing material, and may consider that in future jobs.
I doubt that you'll be able to get the shingles off without destroying the existing foam. At the very least, tear-off will have to be tediously slow.
I think this would classify as a "hot" roof, since it has no ventillation and has insulation directly below the shingles.
No electrons were harmed in the making of this post.
John--
http://forums.taunton.com/tp-breaktime/messages?msg=34292.1
Here's a link to a thread on a roofing job where we put 3" of polyiso foam board on top of a 2x6 roof. This one happened to be finished in steel and was very steep (each of which raised its own special issues), but if you want to put up a cold roof, do it this way, skip the strapping, and just nail ½" ply on top of the crib, then felt and shingle on top of that.
If you use 3" nails thru shingles + 2½" of foam directly into the deck, the shingles risk sliding downhill because the moment arm of ½" of nail tip into the meat vs the weight of the shingle 2½" away from the fulcrum (roof deck surface) will effectively quintuple the racking force the shingles exert on the fasteners. Over time, they'll slide....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Whoa, that is one steep slope. Some sore calf muscles after that job? Turned out great, and good job on the post and photos, real helpful.
Not too sore on the calves, actually. At 25-in-12, it was just a tad too steep even for my 65-degree jacks. Laying the heel of the jack over a 1x brought the staging planks dead level, so it was no worse than walking plates.
It was actually not that bad to work on; whatever I was doing was sitting right there in front of me 90% of the time. Not much bending over required on that job....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.