Cost-effective double stud wall with interior wall as load bearing?
For a two-story home with double stud walls in a cold climate, it seems you avoid a lot of thermal bridging if the rafters/TJIs for the second floor are supported by the inside stud wall. I have questions about how to do this “load-bearing inside wall” assembly most cost-effectively. The approach needs to be something a small crew with no crane can implement (so ballon framing is out).
Joe Lstiburek, worried about condensation on the inside of the wall, advises placing the structural sheathing on the outside of the inside stud wall, making it the primary air and vapor control barrier. But this seems a very labor intensive/expensive way to do things: (1) it requires a second layer of sheathing and house wrap on the exterior stud wall, and (2) it requires two steps to install the insulation (inside and outside the structural sheathing). It seems debatable whether the condensation risk warrants all this effort, and I’m wondering if the following wall assembly (which accepts the condensation risk) is a cost-effective alternative:
— build a standard 10.5″ double stud wall, with load on the inside
— put a class II vapor barrier on the inside of the inside wall,
— put the other control layers on the outside of the outside stud wall.
— let the cavity dry only to the inside.
— use metal strapping on the outside of the inside wall as sheer bracing.
This wall requires only one layer of (non-structural) sheathing, and insulation is done in one step, which seems more cost-effective than the Lstiburek wall. But unlike the Lstiburek wall, it requires installing the class II vapor barrier and the metal shear bracing. Thanks for any advice about the proposed wall, and in particular about how easy it is to build relative to alternatives.
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