How to Find a Leak in a Roof

How to find a leak in a roof may be the hardest part of fixing a leaky roof. Finding the actual spot where the roof leaks is difficult because water can enter the roof in one place and run down to another before it starts soaking into the ceiling.

You know the roof is bad if shingles are missing or obviously damaged, or when water stains the ceiling or walls. The goal is to find the leak before the entire roof goes bad.

Identifying the true location of roof leaks in the attic.
Identifying the true location of roof leaks in the attic.

If you have an attic, the easiest way to spot the leak is to up there on a rainy day. Water will reflect light, so bring a flashlight along. Once you locate the source of the water, mark the area. On a nice day, have a helper tap on the mark while you’re on the roof. After you pinpoint the location on the exterior of the roof, apply roofing cement or new shingles as needed.

If you don't have an attic or just can't find the source of the leak, you can check several places for problems with moisture or damage:

  • Boots, the rubber seals that are around the electric service and plumbing vent pipes, air vents, and exhaust fan flashing.

  • Ridge cap

  • Flashing

  • Gaskets around pipes

  • Shingles

  • Gutters and downspouts

  • Dormer valleys

    Looking for roof leaks on the outside of your house.
    Looking for roof leaks on the outside of your house.

If you don't want to wait for rain to look for the leak, try bringing the garden hose up on the roof. Run the water over the place where you think the leak might be located. Don't go crazy with the water; be sure to start small. Have a helper stationed in the attic with a flashlight looking for moisture. The water will reflect the light and make it easier to see.

Comments (5)

  1. Posted by Paul
    If using a hose to find leaks on the roof be extra careful as there is increased risk of slipping.
  2. Posted by jennifer
    I fixed the roof but water is still leaking in the bathroom at seceral locations. when i go up on the roof i can not find any holes or cracks. is there a make at home water and setlzer or water and soap thing that i could do to locate the holes???? please help
  3. Posted by Ray Unseitig
    Jennifer: I think you did not "fix" the roof if water is still coming in. :-) The bathroom is a clue, there probably a vent pipe going out thru the roof for the traps in the sink, toilet, and tub. Those pipes go thru a roof jack, (metal flashing) where the pipes penetrate the roof. That's possibly the culprit. We don't know what type of roof you have. Sloped or pretty flat. Shingles or rocks over a hot mop of built up layers. You could try caulk aroud the pipes, but it's more likely where the metal flashing is contacting the roof. If rock, sweep back rock and apply "emulsion" from Home Depot, like paint or coating. It gets messy. Hot mop roofs on residential applications don't last more thatn about 20 yrs. if you are lucky, then it's time for a new roof. Work up hill from the leaks and sideways a bit. It's hard to guess at fixes with proper suggestions. The other flashing penetration is a vent for a fan, make sure it has a little "hat" where it is supposed to be so rain does not go straight in. You probably have one or 2 bad spots, that come out all over below. You don't have a hot water heater or ac unit up in the attic do you??? Hope this helps. Ray (raise roofing)
  4. Posted by Sue
    Condo has cathedral ceiling. Attick stops before the roof starts sloping. Have had water problems for 4 years at the front of the unit, right over one of the living room windows. Repaired the fire place, replaced the firewall, caulked everywhere possible. Roof was redone 10 yrs ago. The last thing is a vent 4'' below the gable. Sometimes when it rains it doesn't leak, other times it does. Any other suggestions. Totally at a loss.
  5. Posted by Frankie Beckwith
    new roof was put on brick home before my husband & I purchased it, @ 7 years ago. I closed in the patio for a studio, which closed in the brick chimney (and by' closed in' I mean the backside of chimney which used to be outside in now inside). Because of where the drip is, I believe the leak is coming from the flashing around the chimney, but on one can seem to find a reason, or the source or the location of said leak. The chimney is now in good condition; because of the leak, we found some of the brick crumbling and that has been repaired. The good thing is it's in a room that doesn't really matter, but I really would like to find the source and fix it. Previous homeowners 'don't remember' who replaced the roof. Any thoughts or idea would be greatly appreciated. Thank you Frankie

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