Parts for this step · tap one to find it
A leak at a plumbing vent on an asphalt-shingle roof (6-in-12 pitch, architectural shingles at 5⅝ in exposure). The pipe’s rubber boot has cracked, water has softened a patch of roof deck, and six shingles around it are damaged. The rest of the roof is sound, so it gets repaired, not replaced. Everything that comes off and goes back on is listed below.
≈½–1 day for a small crew
This is a typical example, not a diagnosis of your roof. Shingle and boot instructions differ by product, so the wrapper and the boot’s instructions win wherever they differ from this guide.
The search starts at the ceiling stain and works uphill. Water that gets in at the pipe runs down the underside of the deck and drips off at a low point, so the stain is often a few feet downslope of the real opening. Here the roof is shown see-through.
≈1 hr · Stain ≈2 ft downhill of where the water got in
Parts: 1 × Water path, traced from the stain
Check every opening upslope of a stain before blaming shingles: pipes, vents, skylights, chimneys, walls that meet the roof. A cracked pipe boot is one of the most common leak points on a shingle roof.
Each shingle is glued to the one below by its sealant strip and held by two rows of nails: its own, and the nails of the course above, which pass through its top edge. A flat bar breaks the seals and lifts the nails without tearing the courses that stay.
≈30 min · 6 shingles in 4 courses · the shingles above and beside the opening are lifted, not removed
Parts: 6 × Damaged shingle (comes off)
Seals break cleanest when the shingles are cool, early in the day; hot shingles tear and cold ones crack. Lift the courses above only as far as needed, and keep the old shingles for matching color and exposure.
With the shingles off, the cracked boot slides up off the pipe. The wet underlayment is cut away and the deck is probed; the soft wood around the pipe comes out, cut back to the centers of the rafters on each side.
≈45 min · Cut-out 24 × 12 in · side edges on rafter centers, 24 in apart
Parts: 1 × Cracked pipe boot (comes off); 1 × Wet underlayment (comes off); 1 × Soft roof sheathing (comes off)
Push on the deck all around the opening. Soft, dark or delaminated wood comes out; sound wood stays. If the rafters themselves are wet or damaged, that becomes a framing repair and gets looked at before anything is closed up.
Blocking between the rafters supports the patch’s top and bottom edges. The new piece matches the old sheathing’s thickness, gets a hole for the pipe, and is nailed off to the rafters and the blocking.
≈30 min · 2 blocks · 24 × 12 in patch · same thickness as the existing deck
Parts: 2 × Blocking, 2×6 × 22½ in; 1 × Sheathing patch, 24 × 12 in
A patch thinner or thicker than the deck around it shows through the shingles as a dip or a hump. Leave about 1/8 in at the patch edges, as with any sheathing, and fasten it per your local code’s nailing schedule.
The underlayment patch goes on like shingles: its top edge slides under the old underlayment above, and its bottom edge laps over the underlayment below. Then a square of self-adhered leak barrier, slit in an X, slips down over the pipe.
≈20 min · Every lap sheds water downhill · 20 in square at the pipe
Parts: 1 × Underlayment patch, ≈31 × 19 in; 1 × Leak barrier square, 20 × 20 in
Water only runs downhill, so the upper piece must always be on top. A patch laid over the course above it would catch water and steer it under the roof. Lap widths come from the product label; manufacturers such as GAF call for at least a 20 in square of leak barrier at a pipe.
New shingles go back in course order, starting from the bottom of the opening, lined up with the old courses at the same 5⅝ in exposure. The course that reaches the pipe gets a neat hole cut for it.
≈20 min · 3 shingles · 5⅝ in exposure · 4 nails each (per the wrapper)
Parts: 3 × Architectural shingle, matched to the roof; 12 × Roofing nail (length per the wrapper)
Four nails per shingle is typical; high-wind areas often need six. The wrapper shows where they go. Nails driven too high or too low can let the shingle slip or blow off.
The new boot slides down the pipe until its flange lies flat. The bottom of the flange sits ON TOP of the shingles below; the top and sides will go UNDER the next courses. That order is what sheds water around the pipe.
≈15 min · Boot sized to the pipe · ≈2½ in of the lower flange left exposed
Parts: 1 × Pipe flashing boot, sized to the pipe
Match the boot to the pipe size. Manufacturers such as GAF note that a boot installed right lies flat and needs no sealant; piling sealant around it can trap water. Where the fasteners go depends on the boot, so follow its instructions.
The next two courses go over the flange, each cut to fit around the collar. Then the course that was lifted gets new nails, since its old ones were pulled.
≈30 min · 3 shingles · upper shingles over the flange, flange over the shingles below
Parts: 3 × Architectural shingle, matched to the roof; 24 × Roofing nail (length per the wrapper)
Keep nails out of the collar area, and don’t reuse old nail holes. Old holes left in the lifted shingles get a dab of roof cement.
The shingles that were lifted had their seals broken and may not re-bond on their own, so they get a few dabs of asphalt roof cement under their tabs. The new shingles’ own sealant strips bond in the sun’s heat. The course above is shown see-through.
≈20 min · a few dabs under each lifted shingle · count and size per the wrapper
Parts: 1 × Asphalt roof cement, tube
In cool weather, new shingles may not seal for a while; the wrapper says when to hand-seal them too. Too much cement can blister the shingle, so keep the dabs small.
Six new shingles, a new boot and a sound deck patch, every layer lapped so water runs off the roof, not into it.