Watch when it drips. A roof can only let in water that lands on it, so a leak that shows up during rain or while snow is melting, and dries out in between, points to the roof, and that's a call for a roofer. A drip that starts when someone showers, flushes or runs the washer, or keeps going on dry days, points to the plumbing. And damp that's spread out and has nothing to do with the weather may be condensation from the attic or the air conditioning. Here's how to tell them apart without climbing onto anything.
Make the room safe before you investigate
If the water is near a light fixture, an outlet or anything plugged in, deal with the power first. The CDC's advice for wet circuits and equipment is to turn the power off at the main breaker or fuse on the service panel, and to call an electrician if reaching the panel would mean standing in water. Never flip a switch while you're standing in water.
Then put a bucket and towels under the drip, move what you can out of the way, and take photos of the stain before anything is cleaned up. Our roof repair page has a short list of first steps for a roof that's leaking in the rain.
If the drywall is sagging, keep people out from under it. A sagging ceiling or signs of mold is the point where a professional should look at it.
Why the stain can be in the wrong place
Before you blame whatever is directly overhead, know that water moves. It can travel along framing before it drips, so the damage may show up some distance from the real source. On a sloped roof, the spot on your ceiling and the spot where water got in are probably in different places.
So the stain's location is a clue, and timing is the better clue.
Signs it's the plumbing
Ceiling stains are frequently linked to plumbing fixtures directly above them: bathrooms, kitchens and laundry rooms. The water can come from worn pipe connections, failed seals or small cracks in drain lines. Around an upstairs tub, a cracked shower pan or missing caulk might be the cause, and a stain that keeps growing in a large circle could be a pipe.
You can test this yourself:
- Run the fixtures above the stain separately. Shower, then tub, then sink, then flush. Watch the ceiling after each. Running them individually helps isolate the problem.
- Do the meter test. With nobody in the house using water, read your water meter, wait, and read it again. EPA's WaterSense program says if the meter changes at all, you probably have a leak. Its page gives the waiting time, and it lists worn toilet flappers, dripping faucets and leaking valves as common household leaks.
- Check whether it drips on dry days. Water arriving with no rain and no snow on the roof isn't coming through the shingles.
If those point to the pipes, call a plumber. A licensed plumber can pressure-test the lines and look at connections you can't see.
Signs it's the roof
The roof is the suspect when the leak keeps time with the weather: it appears during or after rain, or as snow melts off the roof, and dries out in between. If it only happens sometimes, notice the wind. A leak that shows up only in certain storms may be wind-driven rain coming from a particular direction.
If you have safe attic access, go up during or soon after rain with a flashlight. Look for shiny or wet spots on the underside of the roof sheathing or rafters, and wet patches on the insulation. If it hasn't rained lately, moist spots can be too hard to see. Step only on the joists or on a floored area: step between them and you might put a foot through the ceiling below.
Pay attention to anything that comes through the roof. The flashing around vent pipes, dormers and changes in roof pitch is the place to check.
Leave the roof surface to a roofer. You'll learn more from the attic and from the ground than from a ladder in the rain.
The bathroom leak that turns out to be the roof
This is the leak that can send you to the wrong trade. A bathroom ceiling stain looks like a plumbing problem. But the plumbing vent that comes up through the roof sits near a bathroom or the kitchen, and the flashing around it has a rubber seal. As the rubber breaks down, rainwater can get through the roof and run down to the bathroom ceiling below.
The giveaway is timing again. If the bathroom ceiling only drips when it rains, and the fixture tests above come up dry, ask a roofer to look at the vent flashing. Our guide to a roof leak around a plumbing vent pipe explains how that leak is fixed. A stain beside the chimney points to chimney flashing, and a leak that appears as snow melts is covered in our post on roof leaks caused by snow melt.
When it's neither
There are other causes to rule out, and they need a different call.
Attic condensation. In an attic without enough ventilation, moisture from the house can condense on the underside of the roof sheathing and drip onto the insulation and ceiling. It looks exactly like rain coming through the roof. The clues are moisture spread over a wide area, damp insulation and no link to rainfall. Check that the soffit and ridge vents aren't blocked, and that bathroom exhaust fans don't vent straight into the attic.
Air conditioning. An AC system produces condensation that a drain line carries away. A clogged condensate line, a damaged drain pan or poorly insulated ductwork can put water on a ceiling. If the stain sits under the air handler or a duct run and shows up when the AC is on, call whoever services your system.
Upper-floor windows. When a window isn't flashed properly, wind-driven rain can get behind the siding and run down inside the wall. That can show up as a stain at the top of a wall, and because it's rain, it follows the weather like a roof leak would.
Don't paint over it yet
It's tempting to prime the stain and move on. Homeowners who painted over a stain have seen it come back. EPA's guide to mold puts it simply: the key to mold control is moisture control, so fix the water problem as soon as you can.
Mark the edge of the stain with a pencil. If it grows after the next rain or the next shower, you've learned something.
If you still can't tell
That's fine. You don't need to diagnose it before you call. If the evidence points up toward the roof, or you've ruled out the plumbing and the stain is still there, we can find out.
With a leak, we don't assume the problem is right above the stain. We trace it back to where it starts. We repair asphalt shingle roofs on homes and EPDM rubber on flat roofs. If you'd rather have everything checked, our roof inspection is a detailed assessment of the outside of the roof, the attic and the inside of the house, with a written report of what we found.
Seeing water come through the ceiling when it rains? Book a roof leak repair and we'll trace it to the source, in Allentown and across the Lehigh Valley, or contact us with a photo of the stain. Hablamos español.