How to Fix a Leaking Roof Vent Pipe Boot
Replace a cracked or deteriorating rubber roof vent pipe boot and reseal shingles around the vent stack to permanently stop rainwater leaks into your attic.
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🧰 Required Tools & Equipment
- ✓ Flat pry bar
- ✓ Hammer
- ✓ Utility knife
- ✓ Caulking gun
📦 Materials & Supplies
- ✓ Replacement rubber roof flashing boot
- ✓ Roofing cement or exterior polyurethane sealant
- ✓ 1-1/4 inch galvanized roofing nails
⚠️ Safety Checkpoints & Warnings
- • Work only in dry, clear weather; never walk on a wet or frost-covered roof.
- • Ensure the extension ladder extends at least 3 feet above the roofline and is secured at the top.
- • Wear soft-soled, non-slip work boots and maintain three points of contact on ladders.
📋 Step-by-Step Guide (5 Steps)
Inspect and Unseal Surrounding Shingles
Locate the leaking vent pipe and carefully slide a flat pry bar under the tabs of the shingles covering the top and sides of the metal flashing flange. Gently break the adhesive bond holding the shingles together without tearing the asphalt. Keep the pry bar flat against the roof deck to avoid punching through.
- • Shingle tabs directly above and beside the flashing flange are lifted and separated cleanly.
- • The underlying metal flange is partially exposed along its sides and top.
- • Bending shingle tabs too far back, causing them to crease or crack.
- • Prying on shingles that overlap the bottom edge of the flashing.
Remove Old Fasteners and Flashing
Work the pry bar under the nail heads securing the old flashing flange to the roof deck and pull the nails out. Carefully slide the entire damaged flashing up and off the vent pipe, taking care not to rip the overlapping upper shingles. Clear away any loose debris or old dried sealant from the roof deck.
- • Old flashing is completely removed from the pipe.
- • Roof deck around the pipe is clean, flat, and free of old protruding nails.
- • Leaving rusted nail heads sticking up in the roof deck.
- • Yanking the flashing forcefully and tearing the bottom underlayment.
Fit the New Flashing Boot Over the Pipe
Lubricate the inside of the new rubber collar with a drop of water or soapy water for easier sliding. Push the new flashing down over the vent pipe until the metal base sits flat against the roof deck. Tuck the top and sides of the metal flange underneath the upper shingles, leaving the bottom flange resting on top of the lower shingles.
- • Top half of the flashing flange is completely hidden under upper shingles.
- • Bottom edge of the flashing flange sits fully on top of the lower shingle course.
- • Rubber collar forms a tight, unrolled seal around the pipe.
- • Tucking the bottom edge of the flashing under shingles, which channels rainwater beneath the roof.
- • Tearing the rubber collar by forcing it onto a rough PVC or cast iron pipe edge.
Fasten the Flashing to the Deck
Lift the overlapping shingles and drive 1-1/4 inch galvanized roofing nails through the pre-drilled holes or corners of the flashing flange into the roof deck. Place two nails along the upper side corners underneath the shingles and two nails near the exposed bottom corners. Drive nails flush without crushing the metal flange.
- • Galvanized nails driven flush into all four corners of the flashing flange.
- • Flange lies completely flat against the roof with no buckled edges.
- • Over-driving nails, creating dents that collect standing water.
- • Driving nails too close to the rubber collar.
Seal Fasteners and Reseal Shingles
Load a tube of roofing sealant into the caulking gun. Apply a generous dab over every exposed nail head on the lower flange. Lift the overlying shingle tabs and apply a quarter-sized dollop of sealant beneath each tab, then press the shingles firmly down onto the flashing and roof deck.
- • All exposed nail heads are fully encapsulated in smooth mounds of black sealant.
- • Surrounding shingle tabs lie completely flat and adhere securely to the base.
- • Leaving lower nail heads exposed to open weather without sealant.
- • Smearing sealant across the bottom drainage edge of the metal flange, blocking runoff.
Credit: inspired by an original tutorial by This Old House — watch the original on YouTube.
Don’t have everything?
- No Flat pry bar? Stiff putty knife or wonder bar
- No Replacement rubber roof flashing boot? Slip-over repair collar (temporary fix only)