The 10 Most Common Causes of a Leaking Roof


A leaking roof can be a cause for panic for many people. The good news, though, is that the vast majority of leaks that you’ll find aren’t because your entire roof is failing and needs to be replaced. In fact, the majority of roof leaks are often due to much more easily rectified problems, as well as to much less expensive problems than a full roof replacement will be. Taking care of a roof leak as soon as you notice it, however, can help prevent further deterioration that may lead to a roof replacement, as well as to things such as mold, mildew, and interior damage. So if you find a leak in your home, don’t panic; instead, use this list of the 10 most common causes of a leaking roof to determine and fix the problem before it gets worse.

Cracked Flashing

The single most common cause of a leaking roof is a crack in the flashing, or thin metal sheeting, that surround protrusions in your roof such as chimneys or skylights. Flashing can wear out and crack long before your roof wears out, which is why leaks in this area are so common.

To fix the problem, just lift the shingles covering the edge of the cracked flashing away, then pull up the old piece. Use it as a template to cut the new piece of flashing to size, then nail it in place using the same pattern as the old roofing nails. Cover the nail heads with sealant and the repair is made.

Broken or Cracked Shingles

Sometimes leaks are caused by a cracked, broken, or missing shingle on your roof. These are usually fairly easy to spot, as well as to replace. Shingles can crack due to impact, such as a hailstone, as well as simply due to age or wear and tear. As long as the rest of the shingles are in good condition, you can usually replace the broken one.

Lift up the shingles that are covering the edges of the cracked shingle, and pull it up. Set in a new shingle and nail it into place before allowing the surrounding shingles back down.

Lack of Sealant in Valleys

A valley is any section of roof where two slopes meet at the bottom. Because water has a tendency to pool here, this area needs to be sealed to prevent leaks in the future. If the area wasn’t sealed properly, or if the sealant has come loose over the years, you may get a leak here after a heavy rain.

To fix this, simply coat the bottom of the valley with roofing sealant, making sure that you overlap up the sides of the valley slightly to get good coverage.

Cracked Vent Booting

Your stack line, or gas vent, is a plastic pipe that extends about two-feet off the top of your roof. It has a boot or escutcheon around the base, which helps prevent water from leaking in around the vent. Over time, this boot can crack, which can allow water to seep in.

Pry up the old boot using a pry bar to pop any nails or adhesive loose. Slide on a new rubber boot over the vent and use roofing caulk to seal it to the shingles.

Ice Dams

If you have a leak begin in the middle of winter, you likely have an ice dam to blame. Ice dams are formed when melting snow on your roof collects at the edges and refreezes. This can force water up beneath your roof shingles, which in turn shows up inside as a leak.

To fix the problem, do your best to remove snow from your roof in a timely way to prevent the ice dams from forming. After they have formed, fill a pair of pantyhose with ice melt and stretch it out along the edge of your roof to melt the ice and stop water from backing up.


A large percentage of roof leaks are due to skylights being improperly sealed or installed. The flashing around the skylight may have failed, the sealant may have come loose, or the glass itself could be cracked.

After you ascertain that the glass is in good condition, try caulking the edges of the skylight. If this doesn’t work, you may need to replace the flashing around the edges to stop the leaks.

Clogged Gutters

Gutters are important for directing rainwater away from your roof. If they become clogged, however, they can cause water to back up beneath your shingles. If the leak is near a gutter, and the gutters haven’t been cleaned recently, this could be the cause.

The best way to fix this problem is simply to free the old leaves and debris from the gutters to get them moving again.

Cracked Chimneys

Sometimes the flashing around your chimney is in good shape, but the bricks or mortar of the chimney itself could be cracked and allowing water to seep in. Always start with inspecting the base of the chimney itself; if the flashing appears to be intact, check for cracks in the chimney itself. Minor cracks can be sealed with tar, but larger cracks may require your chimney to be repointed.

Condensation in the Attic

Sometimes what appears to be a roof leak isn’t a roof problem at all. If your attic isn’t properly vented, then warm moist air from the floors below may be gathering up there. In time, the condensation may build up enough to cause it to leak back down into your ceilings.

The way to tell for sure if it’s your attic and not your roof is to take a look up there; if you see a lot of widespread mold or mildew, then it’s likely that condensation is the problem. The best way to fix this is by having attic ventilation installed that can keep air circulating and prevent moisture build up.

Wear and Tear

Sometimes leaks are due to the loss of the protective granules on your shingles. This can occur if you’re going up on your roof too often, either to fix the satellite dish, retrieve a Frisbee, or just to shovel off the snow. Try to stay off your roof as much as you can, as these types of leaks are the kind that are most likely to lead to a full roof replacement.

To determine if this is the problem, as well as to correct it, have a roofer come out and do an inspection for you. In the meantime, stay off your roof as much as you possibly can.

Stop Leaks

Many people put off fixing roof leaks because they’re concerned that the problem will cost too much money. Unfortunately, the longer you wait to fix a leak, the worse the problem is going to get. Fixing a leak as soon as you find it is the most cost effective way to deal with a roofing issue. Remember that a leak can have a lot of causes, so don’t automatically assume that each time is going to be the worst case scenario. Be sure to inspect your roof each time you find a leak to make the best possible repair.

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