Water stain on the ceiling: what it means and what to do

First, check whether it’s still wet

A stain is a record of water that came through the ceiling. The first thing to find out is whether that water is still coming.

• Look for sagging. Shine a flashlight across the ceiling from the side. A bulge, a soft-looking patch or drywall tape pulling loose means water may be sitting on the drywall. Keep people and pets out from under it, and don’t press on it or poke a hole to drain it. A waterlogged ceiling can come down.
• Check the light fixtures. If the stain reaches a light, a ceiling fan or a smoke alarm, don’t use the switch. The CDC says to turn off the power at the main breaker when electrical circuits or equipment are wet or near water, but only from a dry spot. If you’d have to stand in water to reach the panel, call an electrician.
• Touch the edge, not the middle. If nothing sags, touch the drywall at the edge of the stain. Cool, damp or soft drywall points to an active leak. Dry and firm is a good sign, but it doesn’t prove the insulation above is dry.
• Mark the edge. Trace the outline lightly in pencil and write the date beside it. Look again over the next day or two, and after rain, after a shower upstairs, or after the AC has run all afternoon. A stain that crosses your line is still getting water.
• Take photos of the stain, wide and close up. Arizona’s Department of Insurance and Financial Institutions advises taking pictures of the damage before any plumber or restoration contractor shows up.

Fresh stain or old stain?

You can’t date a stain by looking at it, but a few signs point one way or the other.

Signs of a fresh or active leak:

• The stain is darker in the middle or has a damp-looking edge.
• It’s getting bigger, or a drip has started.
• The drywall feels cool, damp or soft.
• The paint is bubbling, or the stain showed up in the last few days.

Signs of an older leak:

• The stain is dry and firm and hasn’t changed in weeks.
• It has a brown or yellow ring at the edge. Several rings, one inside another, often mean the spot got wet and dried more than once.

An old-looking stain isn’t automatically a finished problem. The Smart Home Water Guide, from the City of Phoenix and other Valley water providers, notes that leaks may be intermittent, happening only while a water-using device is running. A stain that darkens after every shower upstairs, or on every hot afternoon, is an active leak even if it looks dry most of the time.

Where ceiling stains come from in Valley homes

Water seldom drips straight down from its source. It can run along a joist or spread through the insulation before it soaks through, so the stain may be a few feet from the leak. Where the stain sits and when it changes tell you the most.

The AC condensate drain or pan

If your indoor AC unit, the air handler, is in the attic or a closet, suspect it first for any stain nearby. An air conditioner pulls moisture out of the air, collects it in a pan under the coil and sends it out through a condensate drain line. ENERGY STAR’s maintenance checklist warns that “a plugged drain can cause water damage in the house and affect indoor humidity levels.”

The Department of Energy’s Building America Solution Center, run by Pacific Northwest National Laboratory, says clogged drain lines and overflowing pans from equipment in attics and closets “can go undetected long enough to cause severe water damage.” It also notes that older galvanized steel pans can corrode over time. A stain that grows during the cooling season, on days without rain, near the air handler or along the drain line, points here. Our guide to an AC leaking water through the ceiling covers what to do and what the HVAC technician checks.

A bathroom above

On the ground floor of a two-story home, a stain under a bathroom often traces back to a toilet, tub, shower or sink on the floor above. These leaks tend to show up when the fixture is used, so a stain that darkens after someone showers or flushes is a strong clue. A plumber finds and repairs the leak.

Supply pipes in the ceiling or attic

Some homes have water lines running through the attic or between floors. A leak in one of those runs whether or not anything is turned on. When you’re hunting a continuous leak, the Smart Home Water Guide says to look for damp spots and water stains on ceilings and walls, and notes that most interior pipe leaks occur on hot water supply lines because of expansion and contraction from temperature changes.

Your water meter can help confirm it. With every faucet and water-using appliance off, the same guide says a moving sweep hand on an analog meter means a continuous leak. If that’s what you find, see burst pipe water damage.

Rain getting in through the roof

A stain that appears or grows during or right after heavy rain usually points to the roof, a vent or other opening in it, or a clogged roof drain. The National Weather Service says the heaviest rain in Arizona falls during the summer monsoon. A roofer repairs the roof. The wet insulation and ceiling inside are a separate job, covered in our guide to water through the ceiling after rain and on the rainwater damage page.

If you have an evaporative cooler on the roof, the University of Arizona’s Water Wise program notes that a sticking float valve lets the water “run continuously,” and that split seams or a rusted tray could cause a leak.

Why paint alone isn’t a fix

Stain-blocking primer hides the mark. It doesn’t stop the leak or dry anything above the ceiling. The EPA’s advice is direct: “Do not paint or caulk moldy surfaces. Clean up the mold and dry the surfaces before painting. Paint applied over moldy surfaces is likely to peel.” Joint EPA and CDC guidance adds that painting or caulking over mold won’t prevent mold from growing.

The bigger issue is what you can’t see from below. The EPA lists the back side of drywall, the upper side of ceiling tiles, and roof materials above ceiling tiles among the places mold can hide. It also says that if you clean up mold but don’t fix the water problem, “most likely, the mold problem will come back.” So the order is: fix the source, confirm the ceiling and the space above it are dry, deal with any mold, then paint. Our guide to the signs of hidden mold lists what to watch for afterward.

If your home is older, don’t sand or scrape the stained area either. The EPA lists textured paint and patching compounds used on walls and ceilings among materials that may contain asbestos, and says testing is the only way to know. It also says homes built before 1978 are more likely to have lead-based paint.

When a stain needs more than a repair

The repair and the water damage are separate jobs. An HVAC technician fixes an AC drain or pan, a plumber fixes a pipe or a bathroom leak, and a roofer fixes the roof. None of them dries the ceiling. Call a restoration provider as well when:

• The ceiling sags, feels soft, or the tape or paint is coming loose
• The stain keeps growing after the source was fixed
• You don’t know how long the leak has been going on
• The room smells musty
• The stain is under an attic air handler, a bathroom or a supply line

The EPA advises drying water-damaged areas within 24 to 48 hours to prevent mold growth. By the time a stain shows on the room side, water has already soaked through the drywall, and the insulation above may have been wet for longer.

What a restoration provider checks

A provider will typically:

• Take moisture readings on the ceiling from below and across the attic from above, with a moisture meter and often a thermal camera. The wet area above can be wider than the stain.
• Check the insulation. For clean-water damage, the EPA’s cleanup table says wet fiberglass and cellulose insulation should be discarded and replaced.
• Decide on the drywall. The EPA says drywall may be dried in place if there’s no obvious swelling and the seams are intact. If not, it’s removed and replaced.
• Look for mold on the back of the drywall, the framing and the insulation. See mold remediation for what that work involves.
• Dry the area with air movers and dehumidifiers, with readings recorded until the materials reach dry targets.

If the water came from an AC drain, a water heater or an appliance, the water heater and appliance leaks page explains how the cleanup fits around the repair. Before anyone starts, look up their contractor license with the Arizona Registrar of Contractors and ask for the scope of work in writing.

Good questions for the provider:

• How far does the wet area go, both above and below the ceiling?
• Does any insulation or drywall need to come out, and why?
• Will you share photos and moisture readings I can give my insurer?
• What readings should I see before the ceiling is patched and painted?

What to do first

1. Keep everyone out from under a sagging ceiling, and don’t use wet light fixtures.
2. Mark and date the edge of the stain, and take photos.
3. Call the trade that fixes the source.
4. Have the ceiling and the space above it checked for moisture before anyone paints.