Why is my ridge cap leaking?
Short answer. Ridge caps leak when cap shingles crack, lift or blow off, when the nails holding them back out or are left exposed, or when a ridge vent under them lets in wind-driven rain because it is damaged, the wrong type, or installed with the slot cut too long. Leaks near the peak that appear only during windy storms usually point to the ridge vent rather than the caps themselves.
Common causes
- Cracked caps: cap shingles are bent over the peak, and caps cut from 3-tab shingles or installed in cold weather crack early.
- Wind damage: caps sit at the highest, windiest point, and once their seal breaks they lift.
- Nail problems: every cap is face-nailed under the next one, and the last cap's nails are exposed and must be sealed.
- Ridge vent issues: crushed or cracked vents, vents without baffles that let wind push rain through, and vent slots cut all the way to the ends of the ridge instead of stopping short as the vent maker specifies.
- Short nails: fasteners through a ridge vent must be long enough to reach solid decking.
How to tell which
From the attic during a windy rain, look along the ridge. Drips spread along the vent slot point to the vent; a single wet spot points to a cap or nail. Stains near the high point of a vaulted ceiling often trace to the ridge.
The repairs
- Replace cracked or missing caps with purpose-made hip and ridge shingles that match.
- Seal exposed nails on the final cap.
- Replace a damaged or unsuitable ridge vent with a baffled vent designed to resist wind-driven rain, installed with the correct nails and slot length.