How to Fix a Leaking Roof Vent

Most roof vent leaks happen around the flashing or boot seal and can be fixed by replacing the rubber boot, resealing the flashing, or applying roofing cement to small gaps.

  1. Find Where Water Enters. Start in your attic during daylight hours and look for water stains, wet insulation, or actual dripping around the vent pipe. Follow any water trails upward to find where water is actually entering. Remember that water can travel along pipes or rafters before dripping, so the entry point might be several feet from where you see the damage.
  2. Assess Boot and Flashing Damage. Carefully climb onto your roof when it's completely dry. Check the rubber boot (the cone-shaped seal around the pipe) for cracks, tears, or separation from the pipe. Look at the metal flashing underneath for rust, holes, or areas where it's pulled away from the roof. Also check if the boot has slipped down the pipe, creating a gap at the top.
  3. Swap Out Cracked Boot. If the rubber boot is cracked or torn, slide it up and off the pipe after removing any screws holding the flashing. Take the old boot to the hardware store to get the right size replacement. Slide the new boot down the pipe, position the flashing flat against the roof, and secure with roofing screws. Make sure the boot fits snugly around the pipe with no gaps.
  4. Lock Down Loose Edges. If the flashing is in good shape but has loose edges, lift the shingles around the vent and apply a generous bead of roofing cement or polyurethane caulk under the flashing edges. Press the flashing down firmly and add more sealant on top of the edges. Don't forget to seal where the flashing meets the pipe and any nail holes.
  5. Patch Temporary Gaps Fast. For minor gaps or cracks in the boot while waiting for a replacement, clean the area thoroughly and apply roofing cement with a putty knife. Cover the entire damaged area and extend the cement slightly beyond the crack. For temporary fixes, you can also use roofing tape, but this should be replaced with a proper repair as soon as possible.
  6. Confirm the Leak Stops. Wait for the next heavy rain to test your repair, or carefully spray water around the vent with a garden hose while someone watches for leaks from inside the attic. Check the repair again after a few months to make sure it's holding up, especially after severe weather.