When shingling a roof, certain areas of the surface should be given more consideration than others. The eaves of the roof where runs off, the valleys of the roof where water may sit and the peak of the roof where water first hits are these critical areas. Ridge caps provide ideal coverage for a roof peak. Though you can buy pre-made ridge caps to top cedar shingles, you can also create your own ridge caps with standard shingles.
Install the rest of the shingles as normal, laying the shingles in straight rows across the roof, beginning at the eave on one side and working your way upward. Put roofing felt down before each row of shingles to provide extra coverage. Line up the top row of shingles on the first side of the roof with the roof peak.
Apply the shingles to the other side of the roof from the bottom up. Line up the top row of shingles with the roof peak.
Cut a strip of adhesive membrane long enough to line the entire length of the roof peak. Remove the adhesive backing. Center the waterproof membrane over the roof peak and press it down onto the peak, covering the tops of the shingles on either side.
Lay a second layer of shingles directly on top of the first layer lined up with the roof peak on either side of the roof, so that the tops of the shingles also line up with the roof peak. Cut down the first shingle in that row by half so the top row of shingles cover the seams in the row below.
Install another layer of shingles on top of the top row on the opposite side of the roof as well, but line up the shingles so the top layer protrude above the roof by about 2 inches. Cover all of the nail heads in the top row of shingles on both sides of the roof, using roofing cement. Spread the cement along the length of the roof where the two shingles meet. The cement also creates a waterproof seal between the shingles, much like the seal formed by pre-made ridge caps.