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We have a small old house with a finished attic with no headroom. This house needs more insulation, as ice damming has been a big problem. After spending alot of time in FH archives, we have decided to rip the old shingles off, insulate with foam and cover with metal roofing. We priced the nailbase insulation, but it’s $2 sq.ft. while we can buy the foam and purlins for $.75 sq.ft. Piffin states that he has done many of these jobs with foam and purlins, but when we talk to local builders, they all express concern that the metal roof with snow (we live in northern MI) will pull on the purlins and drag the screws downward through the foam. They suggest 2x4s on edge – basically new rafters – on the roof to attach the purlins to. We didn’t want to break the insulation up with lumber, but we don’t want the whole roof sliding down, either. We thought of 2×4 cleats fastened to the eave of the roof, with a coresponding cutout of the bottom edge of the foam to catch on the cleat, but we don’t know if this would be enough support. The roof pitch is 12/12, and yes, this is a DIY job. Any thoughts and/or experience with this would be much appreciated.
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Linda,
I don't mean to be a smart a**, but my experiences with a 12/12 pitch is to sub out the work. Thats a steep roof to be hefting panels around on!
I do alot of the work on my own job sites but farm it out after the pitch exceeds 8/12. Maybe I'm just a chicken...?
Sorry, I could offer any real advice as I live in Florida and we don't have "rain" loads and our insulation is just a batt of r-30 jammed between the trusses.
Good luck!
Mike
*the big problem which causes ice damming is temperature differences between the roof over the warm house and the colder overhangs. Insulation is a help but ventilation is also crucial to solve the ice damming. Use wooden purloins ( perpendicular to rafters, the same thickness as the insulation. Then install wood strapping, the same direction as the roof slope, then another set of purloins. The first set of purloins will keep the insulation in place, and the next 2 layers of wood will allow for ventilation. When you fasten the wood use spiral air gun nails, or wood screws to resist pullout Make sure the air can enter through the eaves and be ventilated out through a roof vent or better yet a continuous ridge vent. If you are still worried about ice damming make sure use "ice & watershield" on top of the insulation layer, at the eaves, and from any roof opening to the eaves. Metal roofing is an investment and requires proper planning so that your investment is not wasted If you have any further questions, just ask Mike Galt Guelph, Ontario, Canada
*Linda,There is little danger of the strapping bruising the foam if set at 16" to 24" OC. Very little snow will stay on the roof at this pitch (be careful about parking under it) so no weight to worry about and the little that does stay is spread way out. You'll do more damage walking it to install than the weight of snow ever will. And I agree, this is a job for pros, unless you do mtn climbing as a hobby anyway.
*I've done plenty of 12/12 pitched roofs by running an extention ladder from the ground up along the roof.I set it up about three feet from the edge of the roof screw on my metal then move the ladder three feet and so on and so on. It will probably take a 32' or longer ladder to get all the way to the peak. You might be able to rent one locally.I have also built them on site out of 2x4's just make sure an eat your Wheaties that morning cause it will be heavy. I wouldn't worry about the snow piling up on a 12/12, like Piffin said it will usually just slide right off. Good Luck ,Dave
*Thanks for the advice - of course we are doing it ourselves anyway - we already have the shingles off and its not too bad, the roof is only 10' from eave to peak. Next question: we are using the external screw type panels and have gotten conflicting advice about putting sealant or caulk where the panels join together. The salesman says not necessary, "no one does it", but other things I've read say to do it. Any opinions? Thanks
*linda,There was some mention a long time ago in a thread here about how certain types of caulk can erode either the finish or the metal itself, I don't remember which, but I've used silicone in flashing situations without a problem so far.I don't caulk the seams. what are you worried about there--they shouldn't be separated enough to allow anything to get in, right?
*Less than 3/12 pitch use the butyl strip.Not needed on yours.
*Silicone can be hard on the finish.Regardless, follow the manufacturer's specs, not the salesman's I think so's.best, DC
*Wow....Just ask a question or two here...and yaa can DIY!near the stream,aj
*Before you start clean up around the house and think... Where/How will I land if I slide off. I always did that cause if you slide down a 12/12 chances are you'll land on your feet....it's what's under them that could kill you.
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We have a small old house with a finished attic with no headroom. This house needs more insulation, as ice damming has been a big problem. After spending alot of time in FH archives, we have decided to rip the old shingles off, insulate with foam and cover with metal roofing. We priced the nailbase insulation, but it's $2 sq.ft. while we can buy the foam and purlins for $.75 sq.ft. Piffin states that he has done many of these jobs with foam and purlins, but when we talk to local builders, they all express concern that the metal roof with snow (we live in northern MI) will pull on the purlins and drag the screws downward through the foam. They suggest 2x4s on edge - basically new rafters - on the roof to attach the purlins to. We didn't want to break the insulation up with lumber, but we don't want the whole roof sliding down, either. We thought of 2x4 cleats fastened to the eave of the roof, with a coresponding cutout of the bottom edge of the foam to catch on the cleat, but we don't know if this would be enough support. The roof pitch is 12/12, and yes, this is a DIY job. Any thoughts and/or experience with this would be much appreciated.