Where is water leakage from my roof coming from?
Short answer. Water leaking from a roof rarely enters right above the drip, because it runs along the underlayment, decking and rafters before it falls. Start at the stain, go into the attic and follow the wet trail uphill, then check whatever sits above it on the roof, usually a pipe boot, flashing at a wall or chimney, a valley, a skylight or damaged shingles.
Why the drip is in the wrong place
Once water gets past the shingles, it follows the slope of the deck and clings to the underside of wood, wires and ductwork. It can travel several feet along a rafter before it drops onto the ceiling. That is why patching the roof straight above a stain so often fails.
Match the stain to likely sources
- Along an exterior wall at the eaves: gutters backing up under the drip edge, or rotted decking at the edge.
- Where a lower roof meets a taller wall: step flashing or a missing kickout.
- Around the fireplace: chimney flashing, crown or cap.
- Mid-room below a bathroom: a plumbing vent boot or exhaust fan cap.
- Below a valley: a worn valley or a debris dam.
- Around a skylight shaft: skylight flashing, or condensation on the glass.
- Near the center of the house: the ridge cap or ridge vent in wind-driven rain.
Mapping it from the attic
- Go up with a flashlight during or shortly after rain.
- Find the wet spot above the ceiling stain.
- Follow the trail uphill along the rafters and the underside of the decking.
- Mark the highest wet point and measure from the nearest gable wall or chimney so it can be found from outside.
If the trail is dry and the stain is spread over a wide area, it may be condensation rather than a leak. See common leak causes and pipe boot leaks.