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The 6 Most Common Roof Leaks (Causes, How to Repair, & More)

January 14th, 2020 | 10 min. read

The 6 Most Common Roof Leaks (Causes, How to Repair, & More)

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Finding the dreaded brown spot on your ceiling is extremely concerning. After awhile, that water breaks through your ceiling and your scrambling to find buckets or pots to catch the water. 

You don't know what kind of damage your leak is doing to your home. You might even find mold that can harm you and your family.

We here at Bill Ragan Roofing want you to know what could be causing your leak. Because we want you to be as informed as possible about something as stressful as a leaky roof, we're going to give you the common roof leaks we see and how they're repaired.

Let's get to the 6 most common roof leaks, where they'll show up, and how to repair them. 

1. Pipe Boot Failure

The most common cause of a leak I see is where a boot around a pipe fails. A boot is a type of roof flashing that goes around the base of the pipes coming out of your roof and waterproofs them.

There are different kinds of boots a roofer could use such as lead, plastic, copper, etc. Whatever the material, the main job of a pipe boot is to stop water from following the pipe down through your roof and into your home. 

For this kind of leak, I chose the synthetic rubber boot I see fail most frequently, a neoprene pipe boot. UV from the sun breaks down the neoprene and it cracks. Once it cracks, water will run down into a closet, kitchen, bathroom, or wherever you have the pipe coming out of your roof.

cracked pipe boot

Pipe boots will not last the life of the roof. Manufacturers have changed the compound over recent years, but it still will not outlast your shingles.

The pipe boot should last around 10 years, but different factors (location, weather, animals) will ultimately decide how long one will last.  

Where will the roof leak show up? 

The leak can show up in the master bedroom, a bathroom, closet, etc. It’s going to be wherever that pipe is located on the roof. Looking at your roof in the general area of the leak will show you which pipe is causing water to get into your home. 

How is the roof leak repaired?

The simplest way to repair this leak is to install a little rubber collar over the top of the old cracked neoprene pipe boot. The collar will encase the existing flange (the flat rectangular flashing that's around the bottom of the pipe) and should last you another 10-15 years.                     

Before and After Repair of Pipe Boot

2. Improperly driven nails 

The second most common cause of leaks is when a roofing nail backs out of a shingle. Whether it’s air-nailed or hand-nailed, if the nail hits good wood, holds tight and snug, and isn’t overdriven, then you shouldn’t have a problem with it. 

However, if a nail isn’t driven in far enough or driven in sideways, it will cause the head of the nail to work its way back up through the shingle. When it rains, water catches the head as it comes down your roof and follows the nail right inside. 

This doesn’t happen to just the roofing nails used on shingles, but also the decking nails. If the decking nail didn’t hit wood when the framing was done, then the sun has a way of drawing that nail out through the shingle. 

If you’ve got a nail head that’s sticking up, then chances are you will have a leak

Nail Head Sticking Up

Choosing a roofing company with a great history of installing roofs properly will lessen the chances of leaks caused by improperly driven nails. 

Where will the roof leak show up?

The leak could show up anywhere. Wherever the improperly driven nail is located on the roof is where the water will drip down in your home. 

How is the roof leak repaired?

To repair this leak the roofer will have to break the seal on the shingle, lift the shingle up, pull the nail out, and move it. 

If the nail wasn’t driven in straight then they’ll have to pull the nail out, drive it in properly, and then lay some ice and water shield on top of it. If the nail worked its way through the shingle, then they’ll reseal the shingle as well. 

If the decking nail didn’t hit wood, then it's just a matter of moving the nail over so that it catches the rafter. Then they’ll fill the nail hole with some type of cement and reseal the shingle back down.

3. Debris in gutters that stop above a roof-line under a valley

A valley is when two roof slopes meet in a V shape that allows water to flow down a roof freely. When a valley stops in the middle of a roof, it will have a gutter that runs into it so the water can continue flowing down. 

The problem is with the fascia, which is the board that runs along the lower edge of the roof that carries all the gutters. When there’s no flashing applied to the fascia board, a leak will happen. 

This leak won’t happen under normal circumstances. It might be under extreme rain, but when that gutter in the valley gets filled with leaves and other debris, it’ll send water through the path of least resistance. 

Debris in Gutters that Die into a Valley

Once that water gets underneath the soffit (the finished underside of the lower edge of a sloped roof), behind the gutter, it can go anywhere it wants, causing all kinds of damage. 

Where will the roof leak show up? 

The leak will show up wherever the water goes once it gets underneath the soffit. The location of the gutter will determine the area of your home the water enter. 

How is the roof leak repaired?

Repairing this leak is as simple as loosening the gutter and installing 3 pieces of flashing. The flashing is brought behind the gutter, onto the roof, and then the last piece is tucked under the valley. 

Flashing Behind the Gutter

4. Chimney wear and tear

There are several ways a chimney can leak. It could be the metal flashing that goes under the shingles surrounding the chimney.

If it’s brick, it could be the mortar joints. If it rains for a few days, the mortar joints and even the bricks themselves could get so saturated that water will start coming into the interior of your home causing damage to walls and the ceiling.  

Chimney Wear and Tear

It can also be water coming down through the top of the chimney. For example, a masonry top could be cracking from being wet and freezing. And a metal top could just be old and rusted or the fasteners that hold it could have come loose. 

In chimney siding, water can get in the corners where the siding butts into the corner boards. Not only can those boards rot out, but so can the boards behind the chimney that you can’t see. 

Chimney Siding Wear and Tear

Whatever the reason your chimney is leaking, you won’t know the extent of the damage until a roofer gets up there and does an inspection. 

Where will the roof leak show up?

A leak from a saturated chimney will weep water into the walls around the fireplace. For chimney caps, the leak will happen inside the fireplace. 

How is the roof leak repaired?

If the leak is from the flashing around the chimney then a roofer will just go in and reflash the area around it. If it’s from the mortar joints then they’ll have to apply a masonry water repellent to seal it. 

To repair the leaks in chimney siding you'll need to hire a competent carpenter or siding man. For the chase top of the chimney, you’ll need to hire a licensed chimney sweep company for repairs.

Most roofers aren’t going to have the proper licenses and more importantly, the insurance, to perform this kind of work on a chimney. A roofer should be able to diagnose the problem for you but you'll need to hire a licensed chimney sweep to handle the repairs. 

5. Improperly installed skylights 

Skylights have gotten a bad rap over the years. Everybody thinks they all leak. However, for example, a VELUX skylight comes with a 10-year no-leak guarantee and could possibly have no problems for up to 30 years. 

So, what’s the problem? 

Sometimes it’s a component or piece of the skylight. But the main cause of a leaking skylight is an installer not reading and following the manufacturer’s installation instructions. 

It’s sad to say, but I see this kind of leak frequently. This not only reflects poorly on the roofer but also on the skylight company. 

Where will the roof leak show up?

A skylight leak is pretty easy to guess where it’s going to show up. If one is leaking then water is going to come down from wherever the skylight is located in your home. 

How is the roof leak repaired?

Repairing a skylight leak is a matter of taking the cladding and flashing kit off, putting an ice and water shield around it, and then putting the flashing kit back on. That will give it the watertight seal needed to keep water out. 

6. Collar failure around a gas vent

A gas vent is a metal pipe with a cap on it that comes through the roof. These are incredibly important because they make sure any carbon monoxide coming from gas appliances vents out through the roof. 

Most of the time these vents are installed by HVAC workers after the roof has been completed. However, they aren’t trained properly on roofing techniques. They’ll slide a collar over an unsealed pipe and flange thinking it will shed the rain right off of it.

Under normal circumstances, this works. But with a torrential downpour, water can splash under the collar and lead to water running down the pipe. 

Gas Vent Leak

Where will the roof leak show up?

The area around the gas appliance connected to the leaking gas vent pipe is where the water will be. You don’t want carbon monoxide going anywhere in your home, so never try to figure out which gas vent is causing the leak. Leave that up to the professionals for you and your family’s protection. 

How is the roof leak repaired?

Since this kind of leak is around an HVAC installed component it’s difficult and a little tricky for a roofer to repair. What a roofer can do is very carefully raise the collar up, seal it with a dark color caulk, and then slide the metal collar back down into the sealer.

Because of the importance of these pipes, roofers have to be very careful when trying to repair this leak so that carbon monoxide doesn’t go inside the house.

checklist of questions to ask a roofing contractor

Do you need to hire a roofing contractor to repair your roof? 

If you’re a handy person or someone with construction experience you can probably repair some of these yourself. There are resources out there to help like videos or articles you can read to help guide you through the repairs. So no, not everyone has to hire a roofing contractor for repairs. 

Just be warned, repairing these incorrectly yourself can lead to bigger problems. The quality of doing it yourself versus a certified contractor can be drastic.

Your safety is another thing to keep in mind if you choose to repair these yourself. If you’re not used to being on a ladder or walking on a roof, then you shouldn’t be up there, period. No amount of money you try to save to repair it yourself is worth your safety. 

The one thing you definitely should hire a contractor for is to have your roof inspected and maintained on an annual basis. They’ll be able to catch most of the problems in this article before they cause damage to the interior of your home. Regular roof maintenance is the key to stopping a leak before it happens.  

No matter if you decide to repair a leak yourself or if you call a contractor, remember quality roof installation and repairs play a huge role in how much life you’ll get out of your roof


When should you call a roofing contractor to repair your roof?

As soon as you notice the leak. The quicker you get the leak looked at the better. 

You have no idea what hidden damage is being done. If you have one leak, then chances are another potential problem is about to show up somewhere else. 

The entire roof should be inspected when a roofer comes to take a look at the leak. 

How much will it cost to repair your roof leak?

Now you know what could be causing your roof leaks.  Be aware, you won't know if you need repairs or a full roof replacement until an expert gets up there for an inspection.

Now that you finished reading this article, you're ready to learn how much these roof repairs cost. Unfortunately, pricing is something that the roofing industry tries to avoid. 

But we're not like other roofing companies. That's why we're going to give you cost to repair your roof. 

Bill Ragan Roofing company has over 30 years of experience in the Nashville area repairing all the leaks I have talked about in this article and more. Whether you need a leak fixed, a new roof installed, or just annual maintenance, we’re confident we can take care of all your roofing needs.

To learn the the price of a roof repair, check out this article on How Much It Costs to Repair a Roof Leak.

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