We’ve been replacing the wooden shingles on the garage and roof. “Best practice” installation instructions are provided by the Cedar Shingle Bureau and can be seen in a PDF here. It does not, however, provide much in the way of practical tips for installation. Here are a few things I’ve come up with during this process.
The basic idea is that the shingles should be installed with 1/4- to 3/8-in spacing between neighbors; this gap is called a “key.” We’re doing a 5-in exposure, which means the bottom 5 in of the the shingle will be visible, while the top 13 in will be under higher courses. The keys should not line up in any adjacent two courses, that is the gap between shingles in the current row should not be directly over a gap in either the course below it or the one below that. Nails are driven in 1 1/2 in above the exposure line, so in this case they are put in at 6 1/2 in above the bottom of the single. Each shingle gets two nails. I’ve seen guidance saying the nails should be driven in 1 1/2 in from either side, but I’ve also seen 3/4 in from the edge.
Nails should be stainless steel or aluminum. Even galvanized nails will rust due to the compounds present in the shingles. We’re using 1-1/4-in aluminum nails specially made for cedar shingles.
To get each course straight, we measure up from the bottom course each time to mark an even 5-in interval. If we just measured from the course directly below, we’d probably get uneven courses over time, as 1/8-in errors would build up to larger errors. We use a snap line (chalk covered string) to create a straight line between the marks on the edge of the course. This creates the line for the bottom of the shingles.
A straight board with a few nails driven through predrilled holes helps us line up a dozen shingles at a time before we come back and nail them in. The nails are held in extra nail boxes stapled to the board.
We arrange the shingles in three general categories: wide, medium, and narrow. So far, it has worked best to have them above the current work zone so that we can see the sizes available when we’re trying to get the right size to avoid lining up keys. On steeper sections, we slot the shingles into gaps between the sheathing.