How do you fix a leak in a roof valley?
Short answer. Fix a valley leak by clearing debris first, then finding which detail failed: worn or cracked shingles in the valley, nails driven too close to the center, shingles cut wrong, damaged valley metal, or a missing or torn lining underneath. A lasting repair usually means removing the shingles along the valley, installing self-adhering membrane and valley metal or lining as needed, and reshingling with nails kept well away from the center.
Why valleys leak
A valley carries the runoff from two roof planes, so it handles more water than anywhere else on the roof. Pine needles and leaves collect there and dam the flow, pushing water sideways under the shingles, and Georgia's heavy summer downpours test valleys hard.
Common failure points
- Debris dams holding water against the shingles.
- Nails near the centerline. Manufacturers keep nails well back from the valley center; GAF's closed-cut detail keeps them at least 6 inches away.
- Shingles cut wrong in a closed-cut valley, such as upper corners left unclipped, so water runs along the cut edge and under the shingle.
- Worn shingles in the valley, which age faster under heavy water flow.
- Damaged or rusted metal in an open valley.
- No valley lining, or torn underlayment beneath.
The repair
- Clear debris and see whether the leak stops; sometimes that was the whole problem.
- For a lasting fix, remove the shingles along both sides of the valley.
- Replace damaged decking, then run self-adhering ice and water membrane down the valley.
- Add valley metal for an open valley, or set up a closed-cut valley as the shingle maker specifies.
- Reshingle with correct nailing, trimming and corner clipping.
Prevention
- Trim overhanging limbs.
- Clear valleys after fall leaf drop and big storms.
- Keep gutters below valleys clean so water does not back up.
See ice and water shield in Georgia and pine needles and leaves on the roof.