Roof Leak Finder
Last reviewed How we calculate
A roof leak rarely shows up where the water gets in. It runs along rafters, decking and pipes before it drips, so a stain on the ceiling is often some way from the cause. This asks three questions about what you are seeing and points to the likeliest places to look.
Roof Leak Finder
Answer three questions about a leak and see the most likely causes, what to check safely, and who to call.
Answer all three questions. The results list the likeliest places to look, most likely first, with what you can check safely yourself.
Where to look first
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Chimney, skylight or vent flashing
The metal and sealant around anything that comes through the roof crack, lift or rust with age, and they are one of the most common sources of leaks.
What to check: From the ground, use binoculars to look for lifted, rusted or missing metal around the chimney or skylight. In the attic, look for stains or wet wood around the same spot.
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A cracked vent pipe boot
Plumbing vents pass through the roof inside a rubber or plastic collar, which cracks in the sun after some years and lets water run down the pipe.
What to check: With binoculars, look at the base of each vent pipe for split or perished rubber. In the attic, check for water on or around the pipe.
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Step or wall flashing
Where a roof slope meets a wall, overlapping pieces of flashing carry water past the joint. If one is missing or bent, or caulk was used instead, wind-driven rain gets behind it.
What to check: Look where the roof meets the wall for gaps, missing metal or a line of caulk. Inside, stains usually appear on the wall or ceiling just below that junction.
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Damaged or missing shingles
Wind lifts and tears shingles, and old shingles crack and lose their granules. Water then reaches the underlayment and, in time, the deck.
What to check: From the ground or an upstairs window, look for missing, lifted, cracked or curled shingles, and for granules collecting in the gutters.
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An ice dam
Heat escaping into the attic melts snow on the roof, and the water refreezes at the cold eaves into a ridge of ice that holds water back. The water then backs up under the shingles.
What to check: After snow, look for a ridge of ice and heavy icicles along the eaves. The lasting fixes are sealing air leaks into the attic, better insulation and ventilation, and an ice barrier when the roof is replaced.
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Overflowing gutters or a missing drip edge
Blocked or undersized gutters overflow behind the fascia, and without a drip edge water can run back under the roof edge and into the wall.
What to check: In heavy rain, watch the gutters from a safe spot: water pouring over the back edge, or stains on the fascia and soffit, point here.
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Condensation, not a leak
Warm, damp air from the house rises into a cold attic and condenses on the underside of the roof deck and on nail tips, then drips. It can look exactly like a leak.
What to check: In the attic on a cold morning, look for frost or droplets on nail tips and the deck. Check that bathroom and kitchen fans vent outside rather than into the attic, and that the soffit vents are not blocked.
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Not the roof: plumbing, air conditioning or a window
Water that appears in dry weather usually is not coming through the roof. Pipes, air-conditioning drain lines and condensation on ducts are common causes, and windows can leak down inside a wall.
What to check: Note whether the stain grows when a bathroom above is used or the air conditioning runs. A plumber or an HVAC technician can confirm it.
This points to the likeliest places to look, based on common patterns. It is not a diagnosis: a roofer, or for dry-weather leaks a plumber, can confirm the cause.
How it decides
Each answer adds weight to the causes it usually points to. Water around a chimney points at flashing; water after snow points at ice dams; water in dry weather points away from the roof altogether, towards condensation or plumbing. The causes with the most weight are listed first, with what you can check yourself from the ground or the attic.
What to do next
If the likeliest cause is on the roof, photographs from the ground and the attic help a roofer judge it before they climb up. If it points to condensation, the fix is in the attic: ventilation, insulation and air sealing. And if the water appears in dry weather, a plumber is the right first call.
Frequently asked questions
Why is my ceiling stain not under the leak?
Water that gets through a roof runs along rafters, the underside of the deck and pipes before it drips, so the stain can be several feet from where the water came in.
Can condensation look like a roof leak?
Yes. Warm, damp air from the house condenses on a cold roof deck and on nail tips, then drips, often in cold weather when there has been no rain. Frost on nail tips in the attic is the tell-tale sign.
Should I go on the roof to find a leak?
No. A wet roof is slippery, and most of what a homeowner needs to see can be seen from the ground with binoculars or from inside the attic. Leave anything closer to a roofer.