No matter where you live, the roof on your home faces assaults from the weather. Leaks in the valley areas of a roof are relatively common, even when they are not evident in other areas. Roof valley leaks are most commonly attributed to an obstruction that causes a water backup.
Clear the valley area and dispose of any debris that can cause water to back up and pool.
Inspect the shingles and underlayment in the valley of the roof. Ensure they are cut in a straight line and do not stick out into the valley area in order to prevent water from being diverted under the shingles. If the shingles extend into the valley, trim them accordingly with a utility knife.
Inspect the shingles in the areas around the valley and replace any that are damaged. Raise the edge of the shingle located above the damaged one. Pry out the nails of the damaged shingle. Remove the shingle and nail a new one into place.
Coat the area where the shingles meet the valley flashing with roofing cement. Raise the shingles and apply the cement underneath with a flat trowel.
Apply a bead of roofing caulk down the flashing area in the valley, right next to the shingles, to provide a final layer of waterproofing in vulnerable areas.
Regularly inspect your roof to catch potential problems before a leak can cause extensive damage to your home.