Rigid Foam insulation as sheathing?

[Reis Pearson]

I inspected a home built in 2005 and in the crawlspace I found portions of the knee wall there were areas that just had 1" rigid foam insulation nailed to the frame and other areas that were 1/2" OSB and 1/2" rigid foam. I've never seen this before and wouldn't think that this would be acceptable. Any insight?

Thanks in advance!

[Scott Patterson]

I inspected a home built in 2005 and in the crawlspace I found portions of the knee wall there were areas that just had 1" rigid foam insulation nailed to the frame and other areas that were 1/2" OSB and 1/2" rigid foam. I've never seen this before and wouldn't think that this would be acceptable. Any insight?

Thanks in advance!

Some foam products are approved for sheathing. Most polyiso boards are approved for non-structural sheathing. This is one by James Manville http://www.jm.com/insulation/building_insulation/products/can283_ap_foilfaced.pdf Dow & Atlas also makes one and I'm sure other manufacturers do as well..

This is or was a very common sheathing with EIFS.

[Brian Tilton]

It was common in the 70's and 80's to have rigid foam or 3/4 sheetrock as exterior siding as long as there was cross bracing installed in the framing, this was to stiffen the framing as the sheathing was not structural. The code was interpreted differently by many local municipal inspectors the way it was written, so look for a diagonal bracing in the framing from the corners to determine if braced properly.

Brian
The Building Inspector of Cape Cod

[Darrel Hood]

Full sheets of sheathing in the corners can be used in lieu of cross bracing. This may explain the partially sheathed configuration you described.

Darrel Hood
DILIGENT PROPERTY SERVICES