Rigid insulation under cedar shingle sid
charlie44732377
| Posted in Construction Techniques on
Hi
I’m liking the idea of rigid isocyanate 1″ installed on the outside of the framing of a workshop I’m planning, but I want to side it with cedar shingles. Anyone heard of rigid panels backed with 1/2″ ply or OSB, or anyone tried putting rigid panels on the outside of the frame then covering it all with 1/2″ ply sheathing, then 30# felt then shingles? Worried a little about water vapor getting trapped.
Thanks Charlie
Replies
I think your best bet is to use a closed-cell extruded foam panel (blue or pink board) for that application. Iso panels can absorb water and lose much of their r-value if the siding/flashing is anything less than absolutely perfect. In addition, if you are looking at foil faced panels, that would put a vapor barrier on the cold side of the envelope. I have heard of iso SIPS panels with OSB skins but don't think that's what you are looking for.
what climate RU in
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Piffin Coastal Massachusetts pretty cold
take a read of this I wrote to another person.http://forums.taunton.com/tp-breaktime/messages?msg=97517.1typically you do not want the foam on the studs then the sheathing because you lose the shear bracing strength of the sheathing being in direct contact. The shear depends much more then on the ability if the nails it is fastened with to resist bending through the thickness of the foam. With sheathing nailed direct to studs, the shear comes from the ability of the nails to resist shearing ( breaking) straight off.Since it is far easier to bend a nail in foam than to break it off in a 1mm pane, you would need to come up with another way of building in wind resistance, probably with metal let-ins.Then there is the issues I addressed in that link above. , the foam is fine. If you finish the walls, don't use VB also on the inside where it can trap moisture.A shop normally will not produce quite as much moisture as a home, and opening doors to receive and send materials and tools makes some shops more well vented too.Short answer is that you can do it but be aware of these issues.Or you could frame and sheathe normally, then the foam, then straping like the old skip-sheathing over the foam to attach the cedar shingles to. Those shingles would last a lot longer that way
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!