I hadn't seen this detail in the field before it showed up here, but I am pretty excited to see it now. Usually when we talk about interior walls intersecting with exterior walls in the context of energy-efficient framing, we talk about ladder backing as nailers rather than 3-stud wall bucks. And we talk about continuous sealant at the top and bottom plates and along the edges of the stud.
This is much easier and far better.
The end of the interior wall doesn't touch the exterior wall, so there is no need for ladder backing or wall bucks—just room for insulation. Also, the space between the walls, which looks to be conveniently sized at 1 1/2 inches, allows the drywallers to slide a full sheet behind the wall, which will significantly boost the air-sealing potential of the drywall. A break in the drywall at wall intersections creates a 16 1/2–foot gap (8 feet up, 8 feet down, and 1/2-foot over) at each wall.
But if the interior wall is spaced an inch and a half away from the exterior wall, how is it attached?
Of course, the bottom plate is nailed to the floor, so the trick is anchoring the walls at the top.
These guys use metal straps to connect the wall plates. These are the same metal straps that are specified in Advanced Framing (a.k.a., Optimum Value Engineering, or OVE) which calls for (among other things) single top plates instead of double.
A close look at the top of the wall connection shows the strap. The wood on top of the strap is solid blocking for ceiling drywall.
If you are going to have your framers do this, tell them to use a 2x6 block as a spacer for bottom and top plates. This will make the gaps consistent and easy to establish quickly. It should also provide plenty of room for the drywall crew to slide full sheets behind the gap.
Big phat attaboy (phattaboy?) to this framing crew for executing this simple detail, another phattaboy to whoever told them to do it, and a final phattabot to whoever thought it up.
Common Advanced Framing Details (Building Science Corp.)
Building America Special Research Project—Deployment of Advanced Framing at the Community Scale (Building Science Corp)
Toolbase: Advanced Framing Techniques
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