Ceiling Water Stain: Roof Leak, HVAC, Plumbing or Condensation?

Start with when it shows up

The timing of a stain is the best clue. A stain that grows during or right after rain points to the roof. One that grows on hot, humid days with the air conditioning running points to the HVAC system. One that appears regardless of weather, especially below a bathroom, points to plumbing. One that shows up on cold mornings in winter can be condensation in the attic.

Roof leak

Usually appears after rain, often worse with wind from one direction. Often near chimneys, vent pipes, valleys, skylights or walls where a lower roof meets a higher one. In the attic you may see wet decking or dark streaks running down rafters. See how to find a roof leak.

HVAC condensate

Air handlers in attics produce a lot of water in a Carolina summer. A clogged condensate line, a rusted drain pan or a disconnected line can soak the ceiling below the unit. Stains from this source tend to be near the air handler or along the drain line's path, and appear in cooling season regardless of rain. Ducts that sweat in a hot attic can also drip at registers.

Plumbing

Stains below bathrooms, laundry rooms or kitchens on a second floor, or along a line of pipe, that show up whether it rains or not. Toilet wax rings, shower pans and supply lines are common sources. A plumber should confirm.

Bathroom fan ducts

Fans vented into the attic instead of outdoors, or ducts that have come loose, dump warm, wet air into the attic. In cooler weather it condenses and drips. Stains appear near the fan. See bathroom fan ducting.

Attic condensation

In winter, warm, moist indoor air leaking into a poorly ventilated attic can condense on the cold underside of the roof decking and drip back down. See condensation vs roof leak.

Why it matters

Each source has a different fix, and paying for a roof repair won't stop an HVAC leak. A roof inspection that includes the attic usually tells you whether the roof is the cause. Whatever the source, water damage to drywall, insulation and framing should be repaired once the leak is stopped — something AGCS handles as a licensed general contractor (water damage repairs).

Frequently Asked Questions