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The hardest part of fixing a roof leak? Locating the leak. Sure, it’s easy enough to spot water stains on the ceiling or mold on the walls, which are sure signs of a leak. But once water has penetrated the roof, it’s easily diverted by such things as insulation. Even though you may notice the evidence of a leak in the corner bedroom, the vulnerable point in your roof may be quite far removed from that part of your house.
For this reason, roof repair jobs typically begin with a certain amount of detective work. These tips for finding a roof leak will help you solve the mystery quickly and repair the leak before the damage to your roof, and your home’s interior, gets any worse.
Step 1: From inside the attic, inspect the underside of the roof.
Arm yourself with a flashlight and head up to the attic. Be careful up there: If there’s no proper flooring, step carefully from joist to joist. (If you step between the joists, you might put a foot through the ceiling of the room below.)
Once you’ve got your bearings, use the flashlight to examine the underside of the roof. Look for any areas that are darker than the surrounding roof sheathing. If it hasn’t rained recently, moist spots may be too difficult to discern. Mold, on the other hand, has a tendency to linger. If you encounter a patch of mold, which thrives on moisture, chances are you’ve found the vulnerable point in your roof.
Step 2: Follow damaged insulation back to the source of the roof leak.
The underside of your roof may be obscured by attic insulation, and that’s actually helpful for finding the roof leak. Insulation deteriorates more noticeably and more quickly than wood does. If you see damage on one section of the insulation, however, you must remember that the leak itself may be several feet to either side because it diverted rainwater from the source of the leak.
It’s best to carefully remove all insulation adjacent to part of the roof where you notice signs of a leak. That way, you can follow the path of the water from the damaged area all the way to the water’s entry point in the roof. (If you’re going to handle or work around insulation, it’s important to wear appropriate protective gear such as gloves, safety glasses, and a respirator mask.)
Step 3: Inspect the underside of the roof for perforations and vents.
Most noticeable to the eye are leaks caused by an object (for example, an errant nail) that has managed to pierce the roof. Failing any such obvious signs, inspect the roof vents next. These vents are typically near ridges or gable ends, or both. Over time, the seals around vents can gradually weaken and allow rainwater to seep in.
Tried-and-True Advice
“I’ve had to deal with a number of leaky roofs, and have found that most form not where there is a continuous flow of shingles, but where some utility or feature penetrates the roof: Plumbing vents, HVAC system vents, skylights, and chimneys are the most common. Chances are, a failing vent pipe boot or leaking chimney flashing is allowing water to enter and flow down the interior of the roof to the spot where it’s coming through the ceiling. If there’s roof penetration above the location of the leak on the ceiling, it’s likely the culprit.”
—Tony Carrick, Contributing Writer
Step 4: If the weather is dry, use a hose to simulate a downpour.
What happens if you’re desperate to find a roof leak, but dry weather has made your search more challenging? You can simulate a storm. This method requires two people: One person on the roof with a garden hose, and another person in the attic with a flashlight. Working in small sections, the person on the roof sprays the roof with water while the one in the attic carefully examines the underside of the roof for leakage.
By simulating a downpour, you can see firsthand how your roof withstands—or fails to withstand, as the case may be—conditions similar to those of a natural storm.
Step 5: Begin your roof repair.
Leaks only get worse. Act quickly once you’ve pinpointed the location of yours. Fortunately, in many instances it takes only a modest roof repair, like replacing a shingle, to fix the leak. If you don’t feel comfortable on the roof or if the leak seems extensive, hire a roof repair professional to do the work.
