How do you fix a roof vent leak, and how can you tell if a roof vent is leaking?
Short answer. To tell if a roof vent is leaking, look in the attic for stains, drips, or wet insulation directly below the vent after a rain, and check the vent hood and flange from the roof for cracks, lifted edges, or exposed nails. The fix depends on the cause: renail and reseal a loose flange, replace a cracked or hail damaged vent, or reweave a vent that was installed on top of the shingles.
Signs a vent is leaking
- Water stains on the decking around the vent opening, or rust on nails near it.
- A wet spot in the insulation or a ceiling stain lined up below the vent.
- Leaks that appear only in wind driven rain, which point to the hood or baffles.
- Cracked plastic, dented metal, or a missing screen visible from the roof.
Causes and fixes
- Cracked or brittle hood: common after hail and from UV aging. Replace the vent; patching plastic rarely lasts.
- Exposed or backed out nails: remove them, refasten in the correct location, and seal the old holes.
- Flange on top of the shingles: the vent was installed wrong. Remove it and weave the new flange under the upper courses.
- Failed sealant: clean and reseal, but check that the flashing laps correctly, since sealant should be the backup.
- Turbine problems: a wobbling turbine can wear its base and let water in. Replace worn turbines or swap them for static vents.
- Wind driven rain: some low cost vents admit rain in storms, and a better baffled design helps.
Temporary measures
If a vent leaks during a storm, put a bucket and towels in the attic and keep the insulation dry. A tarp can protect the area until a proper repair, but do not seal the vent permanently from inside.
Check insurance
If hail or wind damaged several vents, other parts of the roof may be damaged too. Photograph everything and consider an inspection before repairing. See common roof leak causes and Georgia hail season.