The valley on a roof is where two wings of a building join or dormers extend from the roof. The steps for how to shingle a valley focus on creating a fully water-resistant covering that directs water downward. Flashing beneath the roofing felt forms an extra layer of protection over the valley seam.
Directions for How to Shingle a Valley
- Snap chalk lines parallel with the valley 9 inches from its center on both sides.
- Bring enough 18-inch aluminum flashing up to the roof to cover the length of the valley.
- Line the flashing up with both chalk lines and press it into place down the seam of the valley.
- Use a rubber roller to press the flashing flush with the valley.
- Secure the flashing with roofing nails along its outer edges on both sides.
- Trim flashing with tin snips so that it lines up with the edges of the roof.
- Spread roofing tar with a flexible broad knife along both edges of the flashing.
- Snap two more chalk lines along the valley 18 inches from its center on both sides.
- Unroll roofing felt over the valley and trim it with a utility knife so that it lines up with the new chalk lines.
- Attach the felt with roofing nails but take care not to nail within 6 inches of the valley center.
- Lay a shingle over the valley so that one-third of it is on either side of the valley.
- Use a marker to draw lines on the outer edge of the shingle.
- Move the shingle aside.
- Create another chalk line based on the marker line to guide you when laying shingles.
- Snap more chalk lines 3 inches from the center of the valley.
- When nailing shingles do not drive any nails into the valley beyond this 3-inch border.
- Place your first shingle at the bottom roof edge with a 1/4-inch overhang.
- Cut the tabs off of this first shingle.
- Push the shingle down into the valley and nail it at the corners.
- Subsequent rows must overlap the previous rows by 6 inches.
- Add shingles until you reach the top of the roof valley.
