Many older garages were built much like sheds and pole barns. The studs were set into the soil and siding was attached; if you were lucky, there was a bottom plate that sat directly on the dirt. Later, an asphalt or concrete floor may have been poured, covering the bottom plate (if there was one) and the lower portions of the studs. Over time, exposure to ground moisture may cause deterioration of the bottom plates (sill plates) and the bottom portions of the studs. Repairing this part of the framing isn’t a complex project, but there are a few tricks that will make the job easier.
The first task is to cut out the lower portion of each stud, so that the new sill plate can be inserted between the bottom edge and the floor. The easiest way to do this is to jack up the roof an inch or so and support it while you’re doing the job. You can use a hydraulic bottle jack along with some posts made by nailing two 2 x 4’s together – one that will fit between the jack and the doubled header (top) plate of the wall, and two long enough to wedge between the floor and the top plate. Position the jack on the garage floor at one end of the wall; using that shorter post, slowly lift up the roof on that side. When it is up about an inch, wedge the longer post in place to support the roof at that height. Move the jack to the other side of the wall, raise the roof there to an equal height, and wedge the second post in place. (Read the rest….)