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Q.Here in Wisconsin, I have always built my homes with 2x6 studs, R-19 fiberglass batts, and 1/2-inch OSB sheathing. I am considering switching to 2x4 studs, R-13 batts, and 1-inch R-7 foam sheathing, using metal T-braces for racking resistance. The cost of the two systems appears to be about the same. I like the fact that the foam sheathing stops thermal bridging at the studs. My question is: Will the metal T-braces provide a frame that is rigid enough?

A.Paul Fisette replies: You are correct that wrapping the entire house in foam reduces the problem of thermal bridging at the studs. By elevating the temperature of the stud cavities, the foam also reduces the likelihood of condensation on the interior face of the sheathing.

However, there are three drawbacks to using foam sheathing. First, the foam complicates the exterior trim details at doors and windows. Second, there is the real risk of ants attacking and nesting in the foam. Third, substituting foam sheathing for OSB will seriously compromise a home’s structural rigidity. Metal strap braces alone will not provide the racking resistance that you need. In fact, the technical literature by Simpson Strong-Tie clearly indicates that the metal braces are for temporary use during construction. They are not intended for long-term bracing of the framing. For more information, see "Bracing Foam-Sheathed Walls," JLC, 4/93.