Double-stud walls are a great way to create a thick, well-insulated wall with very little thermal bridging as part of an energy-efficient home. They don’t require designers and builders to learn about new products, and building the house doesn’t require techniques that they are not already familiar with. Builders typically construct the exterior load-bearing wall first, then the floors and roof. The double, interior wall is built afterwards, but is still just an additional stick-framed wall. The tricky part comes when it’s time to frame and finish the windows and doors which will be installed in uncommonly thick walls.
The location of the studs in double-stud walls is not important, they can be lined up, or staggered. Of course, you’ll likely want them to be on 16 in. or 24 in. centers to easily layout sheet goods like sheathing and drywall. At the rough openings for doors and windows, the framing of the outer and inner wall must align perfectly. It is common, as shown in these details, for the rough opening to be laid out and framed with extra space so the carpenters can line the opening with plywood or OSB connecting the two walls, sometimes called a “buck.” The plywood has many purposes. It holds the insulation in the walls, brings the air barrier into the opening, and gives a fastening surface for the drywall returns or extension jambs that will be used to finish the opening.
Doors and windows can be placed flush with the exterior face of the wall, like in a traditionally-framed house (called “outies” in a double-stud wall), they can be placed in the interior wall (called “innies”) or they can even be placed somewhere in the middle (called “in-betweenies”). There are advantages and disadvantages to each.
Placing the windows in the…