How to Caulk a Roof Vent Pipe

A roof has several components designed to work together to prevent leaks from occurring. An especially problematic area is any part of the roof where an object such as a vent pipe protrudes through it, as the joint around the object can be prone to leaking. You can seal a roof vent pipe by placing a rubber roof flange over the pipe and applying caulk when installing a new roof.

Roof flange
Shingles
Roofing nails
Utility knife
Tin snips
Clear silicone caulk or roofing tar

Instructions

- 1
  Lay shingles on the roof until you reach the vent pipe.
- 2
  Slide the roof flange over the vent pipe.
- 3
  Hold shingles in position where you will be installing them along the bottom of the roof flange, but don't nail them to the roof. Mark the outline of the roof flange onto the shingles.
- 4
  Cut the shingles for the bottom of the flange with a utility knife or tin snips.
- 5
  Place the cut shingles into position on the roof and slide them underneath the bottom of the flange. Nail the shingles to the roof.
- 6
  Lift the bottom of the flange up, and apply a thick, zigzag bead of clear silicone caulk or roofing tar to the top of the shingles beneath the flange, then press the flange firmly down onto the shingles.
- 7
  Cut the shingles for the top of the flange, following the same method you used for the shingles on the bottom of the flange.
- 8
  Flip the shingles upside-down and run a thick bead of roofing tar or clear silicone caulk around the edge where you cut the shingles.
- 9
  Place the shingles onto the roof around the top of the flange, and nail them into place.
- 10
  Apply another thick bead of roofing tar or clear silicone caulk along the seam where the shingles and the flange meet.

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