Detailing Wall-to-Low-Slope-Roof Connection
这绝对是一个独特的组装。这将是a low-slope roof with a Bison pedestal deck above. The 20′ x 20′ roof will drain into one scupper. Originally, I was going to order customer tapered foam from Insulfoam, which gives the cricketed slopes, but also insulation. To my dismay, they are 6 months out. SO, my solution is to taper the joists (approved by structural engineer) for the main slope, then build my exterior foam layer, THEN build wood crickets above that.
1) My question on this assembly is about drying this cavity in the PARAPET and CRICKETS. Since this space is UN-vented, I am wondering if my 1/2″ non-insulated Zip Sheathing is will allow the cavity to dry to the exterior. This is mostly outside of most envelopes, but needs to keep water out and allow drying… is there a better material here?
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That looks too complicated.
I would keep it simple and use taped poyiso for the roof and install the deck over that. Something like this:
-drywall
-rafters with batts
-cdx/osb roof deck with taped seams as your air barrier
-2" plyiso tapered as needed (you might want it to be 2" min and taper from there or 2" nominal as you only need 1" for condensation control)
-cover board
-TPO
-patio on adjustable pedestals
This avoid any of the drying issues of the enclosed space as well.
Thanks Akos,
I have not been able to find off-the-shelf tapered foam yet. Just the custom ordering, which has it's supply chain broken down. The specific tapered piece should be 1/2:12 to the West>East and 1/4:12 slope E-W (towards scupper).
Unless I can find these pieces, which I agree would be SO MUCH simpler, I'm not sure how else to do the cricket sections then framing out of wood lumber and batt-filled cavities...
Tapered polyiso is standard item at any commercial roofing place. I would phone around a bit before complicating your life.
The other way to to do is to rip tapered sleepers and nail them to the top of the rafters. Put the roof sheathing over this and now you have a sloped surface. Hard to do with your proposed two way slope but pretty easy if you can change it to a mono slope roof. The insulation batts now get pushed up right against the roof deck so it will leave a tapered gap under between the batts and drywall which is no problem.
Hi Akos,
I like the idea of just finding tapered foam. I like the idea of having a less complicated life.
However, even if I find the tapered foam (which would be great), I still need parapets. And the parapets needs to be wood-framed to finish the siding attachment. Should I be worried about the small cavity between the parapet cripples?
I wouldn't worry about it. You can also always stop the rigid bellow the parapet to allow for the cavity to dry towards the outside.