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"Tight" homes and metal roofing installation...

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Guest User
11/14/2010
What is the proper roofing design for "tight" homes? This will be an ICF home with long (up to 50 foot pitches) 2:12 straight roofs; no peaks, only one small valley where two pitches overlap. The roof construction is 2 X 10 HF with 1/2 CDX ply sheathing and water shield underlayment. Insulation consists of 3"-4" spray foam up underneath the sheathing and filled out with R19 batts. There is a whole-house air exchange system. Is there a warm/cold roof interface in this system? Would drain matting be required under the standing seam metal roofing?
Eric Novotny
An informed customer is the Best Customer!
11/14/2010
You should be good to go direct to deck. The only weak point in you insulation is the thermal bridge that will be (although slight) by the 2 by 10. If you wanted to go full bore on it, you could apply a rigid exterior foam and apply the roof on top of that or put the roof on a system of battens to allow for some over deck venting. I am not sure that either are necessary in your situation and there is no need for any drain matting under the roof. If you stop the air flow, there is no real chance for under deck condensation.
Todd Miller
Isaiah Industries, Inc.
11/20/2010
In addition to the previous comments I will say that you need to make sure that you choose a metal panel which is appropriate for that low pitch of a roof.
Eric Novotny
An informed customer is the Best Customer!
11/20/2010
+1 Missed that one Todd.
Guest User
12/6/2010
Is the height of the seam the major determinant in what is appropriate for a 2:12 roof? How high is high enough?
Eric Novotny
An informed customer is the Best Customer!
12/6/2010
How the panels are linked is the major determinant in acceptable slopes. Mechanical double lock seamed roofs should be fine a 2:12 pitch and in some cases, even lower.
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