How to Fix a Roof Vent Stack

A roof vent stack may start to leak, potentially causing thousands of dollars in damage to your home. If you notice a leak, you can often fix the problem by installing a pipe jack. A pipe jack will enclose the roof vent stack, preventing water from blowing into the stack and leaking.

A pipe jack looks like a large pipe with a cover on top. There should be a generous lip around the pipe area, which will act like built in flashing. In fact, if you are familiar with installing flashing around obstacles on the roof, you should be comfortable completing this project to fix the roof vent stack.

Step 1: Pry away the shingles that surround the vent stack flange. You may need to use a hammer to force a pry bar underneath stubborn roofing nails.

Step 2: Pull away the flashing that surrounds the vent stack flange. Often flashing is attached with roofing cement, you may have to use a roofing knife to remove the flashing.

Step 3: Use a utility blade to remove any caulk and roofing cement around the vent stack flange. Clean the area with denatured alcohol to remove any residue around the areas.

Step 4: Place a pipe jack over the vent stack pipe. The bottom of the pipe jack should touch the roof. Lift the pipe jack up and place a bead of roofing cement on the lip of the jack that would touch the roof. Press the pipe jack into place so it creates a seal with the roof.

Step 5: Cover the bare spots around the pipe jack with new shingles. Use your roofing knife to cut shingles to fit around the pipe jack. Nail down the shingles, with the exception of the row of shingles that would cover the top and bottom area of the pipe jack flange.

Step 6: Leave the bottom area open to allow for water run-off.

Step 7: Cut shingles to fit the top area of the pipe jack flange. Glue them into place with roofing cement, sliding the top underneath the previous row of shingles.