Valleys are where 2 angles of a roof meet creating a V-shape. When you discover a leak coming from your valley there are a few ways you can make the roof repairs.
Closed valleys are where the shingles butt together on top of the metal flashing. To repair leaks in this type of valley start at the bottom and slip a piece of flashing in the shape of a diamond under the butted up shingles. Overlap the pieces of flashing at least 2 inches. Nail each shingle and cover the head with roofing cement.
Metal flashing allow water to flow down the valley
Open valleys have the flashing exposed and the shingles end at the flashing edges. To seal make sure there is no debris in the valley. Check that the roofing material is cut in a straight smooth line on each side. The distance between the shingles should widen from the ridge to the eave at 1/8 inch per foot of valley. Lift each shingle and use roofing cement to coat the area that lies on the valley. Use a cartridge gun to run a bead of roofing cement down the valley next to the shingles.
If you need to patch a valley flashing cut a piece of sheet metal the same gauge as the original flashing. Cut a patch larger than the damaged area and wide enough to slide under the shingles. Apply a bead of roofing cement around the outer edge of the patch slide the patch under the shingles on one side and then the other. Put more roofing cement on the top and bottom of the patch where it lays over the original valley piece. Smooth the cement so water can flow uninterrupted down the valley.
You can also check online for video tutorials on how to repair your flashing. As always be careful if you go up on your roof to do any repairs yourself. If you are in doubt, hire your local roofer to make the repairs for you.
