12 Tips for Finding and Fixing Leaks In Your Roof
Updated: May 15, 2024
You don't necessarily need a roofer to fix a roof leak, but you have to find it first. With these tips, you can find and fix most leaks yourself.
It can be a whole lot easier to fix a roof leak than it is to find it, and you can thank gravity for that. Sure, the location of the drip inside your house may be obvious, but because water tends to seep along the roof decking before it finds a way through, the actual hole in the roofing through which it entered could be far away.
Fortunately, because gravity is involved, you can be almost sure that the hole is higher up on the roof than the drip. But even so, it will probably take some detective work to find it.
I recently had to address a leak from a light fixture in the bathroom. I managed to pinpoint the problem: damaged shingles several feet above the fixture and offset a foot to the right on the steeply sloped roof. Replacing the shingles was easy. Light fixture leaks are surprisingly common, says renovation expert Korey Gregory. “Light fixtures, fans, vents and skylights are almost always at the lowest point. If a property has a leak in the roof or if elevated appliances such as HVAC units start to leak, gravity does the rest of the work and brings the water pooling into these spots.”
You can usually get a rough idea of the vicinity of a leak, and once you do, you’re almost there, says Niki O’Brien, who manages a Colorado renovation company. “Things to look for that could result in a leaking roof include missing or damaged shingles, rusted through or damaged flashing, or curled or lifted shingles.”
Besides soaking your floors and ceilings, a leak can promote mold growth and damage your home’s infrastructure. The sooner you find and fix leaks, the better. Here are 12 tips to get you started.
Look Uphill to Find Roof Leaks
When tracking down a leak, start by looking at the roof uphill from the stains. The first thing to look for is roof penetrations — items poking through the roofing are the most common source of leaks. In fact, it’s rare for leaks to develop in open areas of uninterrupted shingles, even on older roofs.
“Leaks are most commonly found along penetrations in the roofs’ surface, like near skylights, vents, or other areas like valleys that experience heavy drainage,” advises O’Brien. They might be several feet above the drip or to the right or left.
Go Into the Attic, if Possible
Leaks are easier to pinpoint if you have access to the attic. You might see water spots or tracks on the underside of the roof decking, and some of the attic insulation may be soaked. If your ceiling has a plastic vapor barrier between the drywall and the attic insulation, push the insulation aside and look for flow stains on the plastic. Often water runs to openings in the vapor barrier, such as at ceiling light fixtures.
If you can’t see any telltale flow marks, look for ‘shiners’ poking through the underside of the roof. A shiner is a nail that missed the framing member when the roofer nailed down the roof decking. Moisture that escapes into the cold attic from the rooms below often condenses on exposed nails, freezes on cold nights and begins dripping when the attic warms up during the day. Shiners look white at night because they’re frosted. The solution is to clip them flush to the decking.
Use this Trick to Find Difficult Leaks
If a leak is difficult to find, enlist a helper and go up on the roof with a garden hose. Start low, soaking the area just above where the leak appears in the house, and run the hose in isolated areas. For example, soak the downhill side of a chimney first, then each side, then the top on both sides.
Let the hose run for several minutes in one area before moving it up the roof a little farther. Have your helper stay inside the house waiting for the drip to appear and ready to yell when it becomes visible, signaling that you’re in the neighborhood of the leak. This process can take over an hour, so be patient, don’t move the hose too soon, and be ready to buy your helper dinner.
If running water doesn’t reveal the exact location of the leak, don’t be timid. Start removing shingles in the suspect area. You should see evidence of the leak when they’re gone, such as discolored felt paper, water-stained or even rotted wood.
Repair Damaged Plumbing Vent Boots
Plumbing vent boots can be all plastic, plastic and metal, or even two-piece metal units. Check plastic bases for cracks and metal bases for broken seams. Then, examine the rubber boot surrounding the pipe. That might be rotted away or torn, allowing water to work its way into the house along the pipe.
When you notice any of these problems, you should generally buy a new vent boot to replace the old one. But if the boot is in good shape — other than the fact that the nails at the base are missing or pulled free — you might not need a new one. You can remove all the nails and replace them with the rubber-washer screws used for metal roofing systems.
To replace the nails, you’ll have to work the adjacent shingles free on both sides. Unless you have extra shingles, be careful when prying them up to avoid damaging them. Use a flat bar to separate the sealant between the layers, then drive the bar under the nail heads, pop out the nails and drive screws into the nail holes.
Fix Leaky Roof Vents
Check for cracked housings on plastic roof vents and broken seams on metal ones. You might be tempted to throw caulk at the problem, but that solution won’t last long. There’s no better fix than replacing damaged vents. If the vent is in good shape, look for pulled or missing nails at the base’s bottom edge and replace them with rubber-washer screws.
If you have to replace a damaged vent, you can remove nails under the shingles on both sides of the vent without removing the shingles. You’ll find nails across the top of the vent, too, and you can usually work those loose without removing shingles. After you’ve installed the new vent, squeeze out a bead of caulk beneath the shingles on both sides to hold them down and add a water barrier. That’s much easier than renailing the shingles.
Stop Leaks in Walls and Dormers
Water doesn’t always come in through the shingled surface. Wind-driven rain can seep in from above the roof around windows, between corner boards and siding, and through cracks and knotholes in siding.
Dormer walls provide plenty of opportunity for water to dribble down and seep through the roof. Caulk between the corner boards, window edges, and siding can be old, cracked or missing, allowing water to penetrate and work its way behind the flashing and into the house. Even intact caulk may not fully seal against the adjoining surfaces.
If you suspect leaky caulk, dig it out with a putty knife and replace it with a fresh dose of high-quality caulk. While you’re at it, check the siding above the step flashing at the base of the wall. Replace any cracked, rotted or missing siding, ensuring the new piece overlaps the step flashing by at least two inches.
If you still have a leak, remove the corner boards and check the overlapping flashing at the corner. Often, you’ll find old, hardened caulk that needs to be replaced where the two pieces overlap at the inside corner.
Control Leaking at Roof Joints
Complex roofs need special attention, especially at joints where one roofline meets another. The roof in this image leaks during the snowy part of winter and during storms in the summer, no doubt because of poor flashing.
The soffit that meets the roof is one of the toughest areas to waterproof, especially when the roof shows signs of an ice dam. O’Brien says that ice dams “are most often caused by improper ventilation and insulation in your attic or by clogged gutters, which allow ice to build up.” Eventually, water pools behind the dam and works its way back up under the shingles and under the soffit until it finds an opening through the roof.
The solution begins with good flashing:
- Remove the shingles down to the roof decking.
- Slip a strip of adhesive ice-and-water barrier (available where roofing repair products are sold) under the soffit/main roof joint. Depending on how the roofs join, you may have to cut a slot to work it in far enough. It should overlap another piece of ice-and-water barrier laid below, all the way down to the roof edge. This should cover the most leak-prone areas.
- Slide metal step flashing behind the fascia board (the trim behind the gutter) in such a way that the valley flashing laid over the joint where the two roofs meet overlaps it by at least two inches.
- Re-shingle.
Improved attic insulation and ventilation are usually the best ways to prevent ice dams, but they might not be effective in this complicated leaky roof situation. If not, consider installing heating cables on that part of the roof.
Replace Damaged Step Flashing
Step flashing prevents leaks at the base of a wall that intersects the roofline. Each short section of flashing channels water over the shingle downhill from it. If the flashing rusts through, or a piece comes loose, water will run right behind it, and go into the house.
Replace rusted flashing. To get the old flashing out, you have to remove any shingles on top of it and pry the siding loose. Then you can fit new flashing under the siding, affix it to the wall, replace the siding and then replace the shingles. It’s that simple.
Don’t forget to nail it securely in place, or it will eventually slip down to expose the wall. Check out this article for more on installing your own step flashing.
Patch Leaks Around Brick Chimneys
All kinds of bad things can happen around brick chimneys — far too many to cover in this story. Galvanized steel flashing around chimneys can rust through, especially at the 90-degree bend at the bottom, and water can seep into the chimney and onto the roof, where it can rot the decking. You can do something about that.
A quick but relatively long-term fix is simply to slip new flashing under the old, rusted stuff. That way, any water that seeps through will be diverted. The best fix, though, is to cut a saw kerf into the mortar and install new flashing. Here are complete instructions for installing chimney flashing the right way.
Fill Small Holes
Tiny holes in shingles are sneaky because they can cause rot, a leaky roof and other damage for years before you notice the obvious signs of a leak. You might find holes left over from a satellite dish, antenna mounting brackets or just about anything. Don’t forget loose and exposed roofing nails. You need to pull these and either replace them or patch the holes.
Small holes are simple to fix, but if you do it by injecting roofing caulk, the repair may not last very long. Liquid flashing, which is intended for sealing recessed windows, is a far better option. You can also make the repair by fitting metal flashing under damaged shingles.
Don’t Over-Rely on Caulk!
Rarely will caulk or roof cement permanently cure a leaky roof on their own. You should always attempt a “mechanical” roof fix whenever possible. That means replacing or repairing existing flashing or shingles instead of using roof sealant as a leak stopper. Only use caulk for very small holes and when flashing isn’t an option as a leak stopper.
Clean Out the Gutters
This might seem like an unrelated chore, but according to O’Brien, clogged gutters are a major cause of ice dams, and ice dams can cause leaks. When ice backs up past the exterior wall, water can seep through the decking and into the house when the ice melts. The results are stained drywall, mold and water-damaged framing.
This is another reason why gutter cleaning should be on your fall maintenance to-do list.
Originally Published: July 18, 2021
