Neatly fitting inside or outside corners are easily made. It is standard practice to lace outside corners (Figure 8e). On wide exposures this method requires small nails near the Certi-label™ Western Cedar shingle butts to tighten and hold the lapped corners. For these corners use only nails that are corrosion resistant. In double course applications, the exposed Certi-label™ Western Cedar shingle or shake shall be face-nailed with two hot-dipped galvanized or stainless steel casing nails, driven 2" above the butt line, and 3/4" from each edge. Certi-label™ Western Cedar shingles wider than 10" require 2 additional nails and these two nails are driven approximately 1 inch apart near the center of the shingle. Corner boards also can be used to advantage by nailing a 1 x 4 cedar board to a 1 x 3 cedar board, then attaching the preassembled corner to the building (Figure 8a).
It is good practice to use flashing behind Certi-label™ Western Cedar shingles or shakes at the inside corners. They may be butted against a square wood strip (Figure 8b), or they may be fitted one course to the other (Figure 8d). When the latter method is used, courses must be completed on each wall progressively, and can be best applied by working from the corners while alternately fitting one course to the other. (Figure 9)
It is preferred practice to install inside/outside corner flashing to safeguard against the cracking or tearing of Type 30 felt underlayment at these corners.
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