In order to install roofing valleys, first create nail and guide lines, then attach the left side of shingles, attach the right side of shingles, cut off the corners of the right side and seal the edges with roof cement. Place nails 6 inches away from the center of the valley during installation.Continue Reading
In order to install closed-cut roofing valleys:
Mark the nail line 2 feet to the left from the center of the valley.
Place one shingle at the bottom of the valley with one edge touching the nail line. Mark the top of the shingle where it crosses the valley, and place a mark on the roof where the top right corner is. Then, take the shingle to the top of the roof, line the valley mark with the center of the valley and again mark the roof at the top right corner of the shingle. Snap a chalk line between both of the markings on the roof.
Nail down both the left and right sides of shingles on the first row, but then continue up the left side, aligning the bottom left corner of the shingle with the nail line and the top right corner with the guide line. Keep the nails 6 inches away from the center of the valley.
Create a guide line the same way as before, and nail down the other side of shingles. Once installed, mark a cut line 3 inches to the right of the valley center. Place a sheet of metal under the edge of the shingles and cut off the corners, one at a time.
After the shingles are cut, seal the edges with roof cement.