You look up and there it is: a brown ring on the ceiling, or a drip landing on the floor. The first question every homeowner asks is the same one. Do I call a roofer or a plumber?
In a Philadelphia rowhome, the answer isn’t always obvious. Bathrooms often sit right under the roof, the back kitchen has its own low roof, and pipes run through the same ceilings that water from the roof can reach. The good news is that a few simple clues will usually point you in the right direction before you call anyone.
The Quick Answer
If the leak only shows up when it rains or snow is melting, it’s most likely the roof. If it shows up on dry days, after someone showers, or runs no matter what the weather is doing, it’s most likely plumbing.
That one test settles most cases. The clues below help with the rest.
Clue 1: When Does It Leak?
Timing is the strongest clue you have.
- Only during or after rain: points to the roof. Roof leaks can show up hours after a storm, because water travels along the roof deck or a joist before it drips through.
- During snow melt or a thaw: also points to the roof, especially on flat rowhome roofs where melting snow sits on the surface.
- After a shower, a bath, or flushing: points to plumbing in the bathroom above.
- All the time, rain or shine: points to a supply line, which is under pressure and leaks constantly.
Try this: if the weather has been dry for a few days and the stain is still growing or damp to the touch, it’s very likely plumbing. Winter can muddy the picture, because snow and ice can leak days after a storm. We cover one common culprit in the cause of some winter roof leaks.
Clue 2: Which Floor Is It On?
Water from the roof almost always shows up on the top floor first. If the stain is on a first-floor ceiling and there’s a full floor of living space above it, the roof is much less likely to be the cause.
The one big exception in Philly rowhomes is the back building. Many homes in neighborhoods like Point Breeze and East Passyunk have a kitchen on the first floor in the back, with a low roof over it. Some have a bathroom on the second floor directly above the kitchen. So a stain on the kitchen ceiling could be the low roof, the bathroom, or both. In that case, timing (Clue 1) matters even more.
Clue 3: Where on the Ceiling Is It?
Think about what’s above the stain.
- Under a bathroom, or near a tub, toilet or sink: check the plumbing first. A worn wax ring under a toilet or failing caulk around a tub can leak into the ceiling below.
- Along the wall you share with your neighbor: this often points to the roof seam where your roof meets the house next door. We wrote a whole post on who fixes a leak between two rowhomes.
- Near the front or back wall on the top floor: often the roof edge, where the roof meets the parapet wall or the gutter.
- Around a light fixture or vent on the top floor: could be either, but on a top floor with nothing above but the roof, it’s usually the roof.
- Near a radiator or under heating pipes: many Philly rowhomes still have hot water or steam heat. A leaking valve or pipe can stain the ceiling below it, and it often gets worse once the heat comes on in the fall.
Clue 4: What Does the Stain Look Like?
This clue isn’t perfect, but it helps.
- Rings with darker edges that grow after each storm: a classic slow roof leak. Each rain adds a new ring.
- A spot that stays wet and keeps spreading: a steady plumbing leak.
- Bubbling or sagging paint: a lot of water is sitting above the ceiling. Don’t wait on this one, no matter the source.
Clue 5: Check the Roof From Inside and Outside
If you can do it safely, a look from the roof hatch or a back window can tell you a lot. On a flat roof, look for standing water that hasn’t drained a day or two after rain, cracks or bubbles in the roof surface, or a seam that’s lifting near the wall you share with a neighbor. If you have a roof deck, keep in mind that leaks often start under the decking where you can’t see them. Our EPDM roofing page explains why rubber roofs are the go-to under decks, and what EPDM rubber roofing is covers the basics.
Please don’t walk on a wet or icy roof. If you can’t see it safely, leave it to a roofer.
A Simple Test You Can Run
If you still can’t tell, try this on a dry day:
- Mark the edge of the stain with a pencil.
- Run the shower or bath above it for 10 to 15 minutes, and flush the toilet a few times.
- Check the stain again an hour later.
If it grew, it’s plumbing. If it didn’t change, wait for the next rain and check again. If it grows after rain, it’s the roof.
What to Do Right Now
Whatever the cause, a few steps limit the damage. If the leak started during a storm, our roof storm damage checklist also covers what to look for outside.
- Put a bucket or towels under any drip.
- If paint is bulging, poke a small hole in the center of the bubble over a bucket to let the water out. This keeps it from spreading across the ceiling.
- Move furniture, rugs and electronics out of the way.
- Take photos of the stain and note the date and weather. This helps whoever comes out, and it helps with insurance.
- If water is near a light fixture, turn off that circuit at the breaker.
When to Call a Roofer
Call a roofer if the leak lines up with rain or snow melt, if the stain is on the top floor with nothing but roof above it, or if it’s along the wall you share with your neighbor. Flat rowhome roofs can go a long time with small leaks before they show inside, so by the time you see a stain, the roof has usually been letting water in for a while. That doesn’t always mean a new roof. We explain when a repair is enough in my roof is leaking, do I have to replace it?
Top Tier Roofing is a family-owned roofer in South Philadelphia, and we usually offer same-day service. We’ll find where the water is getting in, tell you plainly whether it’s the roof, and if it’s not, we’ll tell you that too. Every job is backed by our 10-year workmanship warranty. Learn more about our flat roof work, browse our roofing FAQ, or call us at (215) 330-2664.
Frequently Asked Questions
Can a Roof Leak Show Up Far From Where the Water Gets In?
Yes. Water can run along the roof deck or a joist for several feet before it drips through, so the stain isn’t always right under the problem spot.
Why Does My Ceiling Only Leak During Heavy Rain?
A small opening, like a worn seam or a lifted edge, may only let water in when a lot of it hits the roof at once or when wind pushes rain sideways. It’s still worth fixing, because it will get worse. See protecting a flat roof from leaks in heavy rain.
Can a Leak in My Neighbor’s Roof Show Up in My House?
It can. In rowhomes, water can come in at the seam where two roofs meet and run along the shared wall into either house.
Is a Ceiling Stain an Emergency?
A dry, old stain usually isn’t. A stain that’s wet, growing, sagging or near a light fixture should be looked at right away.