When dealing with water, air, vapor, and thermal control layers, continuity should always be front of mind. The success of any structure relies on our ability to control what happens to the structure itself and the spaces within.
When looking at a typical house with an attached garage, the house takes priority, as it is the inhabited conditioned environment. Often, one or more of its walls abut an unconditioned garage. The intersection between the two structures is what this detail addresses. In this case, it is a 2×6 wood-framed garage wall intersecting a 2×8 exterior house wall.
Water management is the first order of priority. Here, the 1×3 wood furring rainscreen turns the corner from house to garage, thereby maintaining continuity. This furring was selected for several reasons. First, the 3/4-in. space provides ample drainage for any bulk water that gets behind the siding. That gap also creates drying potential for the wall assembly, as air is able to migrate vertically and assist with drying. Lastly, 1×3 wood furring was the general contractor’s favored approach.
The second priority is air tightness management. The 1/2-in. ZIP sheathing with taped joints serves as the primary air barrier. Note that sheathing runs continuously across the exterior of the 2×8 house wall. When developing a strategy to ensure continuous control layers, we do the “red line test” to determine whether or not a space is inside or outside of the conditioned space. In this instance, the house is inside the conditioned space, while everything to the outside of the ZIP sheathing is outside the conditioned space. Notice the sheathing is not interrupted in any way. It is installed as the primary air barrier, and all subsequent materials are attached outboard of it.
Vapor management is third on the list of priorities. In this detail, although the garage is…