Straight courses of finish siding and sharp-looking exterior trim depend on good prep work on the sheathing and exterior trim surfaces that will be covered with aluminum cladding. A good deal of wall sheathing will already be done at this stage. Now that finish siding is about to be installed, it’s important to make sure the wall surfaces are flat and free of gaps that will cause dips or irregularities when the vinyl is installed. When installing foam sheathing, you can sheathe right over window and door openings, then use a handsaw to cut out the foam from the opening (see the photo on p. 109).
If necessary, install wood sheathing or foam board over any unsheathed areas on which siding will be installed. These areas include the rim joist and headers above windows and doors. Along eave walls, it’s also essential to extend the sheathing between the roof trusses above the top plate of the exterior wall, as shown in the photo at right. This additional sheathing acts as a baffle, preventing attic insulation from spilling out into the eaves. Cut each OSB panel so that there are a couple of inches of open space between the top edge of the panel and the top edge of the roof trusses. This clearance is essential for good ventilation; it allows air to be drawn through the soffit vents and into the attic space.