Finding out where a leak is on your roof isn’t always as easy as it would appear to be. When trying to locate a roof leak, use the following guidelines to assist you. NOTE: whenever you see the words “the leak area,” it refers to an area within a 10 foot (3 meter) diameter of the leak.
Flat or Low-Slope Roofs
Inspect any roof drains near the leak area. If they are plugged or draining slowly, then there is a strong chance that they are the reason for the leaks. Drains are rarely waterproof if they are plugged. They are generally designed and constructed for water to flow in one direction only…down.
Inspect any material seams in the area of the leak. Just because you see “tar” or adhesive sticking out under a lap, it doesn’t mean that the material is adhered properly. Take a flat blade about 2 inches (5 cm) long (like a pocketknife blade), and gently run it along under the lap. If it slides in more than 1 inch (2.5 cm), then the seam should be sealed. If it slides in for the length of the 2 inch blade, it’s a good suspect for a leak.
Look carefully at all penetrations for signs of problems. Problems include holes in the metal flashings, shrunken pitch pan filler, deteriorated caulking, curled flashing flanges that are sticking up through the roof membrane, or any other visible defects. Look for blisters that have been punctured.
Look closely at expansion joint seams. These are often faulty.
Check for splits in the area. Do this by walking the area with your feet close together and taking many small steps, turning in all directions. If there is a split, you’ll see the roof separate between your feet.
If the leak occurs near the edge of the building, check the edge metal. It can separate at the seams and tear the roof membrane in the process.
Check under debris. A lot times, if debris has been sitting on a roof for a long period of time, then it can hold water which will expedite roof deterioration. Bird, rodent, and other vermin nests have been found under piles of debris on roofs.
If you get a freak rain storm that dumps horrendous amounts of water on your roof in a short period of time, and all of a sudden you have half a dozen leaks where before there were none, don’t get overly excited. Most roofs are not designed or constructed to handle that much water all at once.
If you look carefully, and find nothing on the roof, then check your attic or ceiling space. What is mistaken for a roof leak can sometimes be a problem with the plumbing, especially with commercial buildings because fire sprinkler lines usually run along the attic space. This is often identified by a leak occurring when it isn’t raining.
Another problem that is frequently mistaken for a roof leak is a poorly designed roof-mounted HVAC unit. HVAC units can have faulty pans in them which will permit water to enter the building during a rain storm.