5 Causes of a Leaky Chimney and What You Can Do to Fix It | There are many reasons for a leaky chimney. However, the causes can be narrowed down to just 5 main reasons. Depending on the causes of the leak, the methods used to fix the chimney can be different from one to another. It can be as simple as adding a cover to the top of the chimney that you can do yourself or as complicated as leaking bricks that need professional help.

But, whatever the reason is, you need to find the right method to fix the chimney. Let’s dig deeper into the reasons why a chimney leaks and what you can do to repair it on the following page.

5 Causes of a Leaky Chimney and What You Can Do to Fix It

Reason 1 – Rain Going Straight In from Chimney’s Top

This is often considered the simplest reason that causes a chimney to leak and it is not hard to find out why. Chimneys that do not have covers will get a lot of rain easily. The absence of the covers means that there is no barrier that will block the rain falling down to the chimneys directly. In this way, adding a cover to a chimney really makes sense to most people.

The covers placed on top of the chimneys will not only prevent rain from dropping directly into them but also block things like debris. The covers also allow you to avoid birds, bats, and other animals that can cause potential damages on the chimneys. This is perhaps the greatest value of adding covers to chimneys. It is because people in the house can get sick, even die from CO poisoning if animals and other things get the chimneys blocked at the bottom. Though uncovered chimneys are often blamed for water problems sometimes, a metal liner is considered the most common reason for a leak.

How to Fix It

If this is the reason why your chimney leaks, getting a chimney cover is the best solution you can take. Though it sounds simple, you might need the help of professionals to install the cover. Things related to the chimney cover installation are not as easy as you think.

Reason 2 – Cracks in the Chimney Crown

If you have a chimney, you might notice that it has a cement part found at its top. That’s the chimney crown. Looking at your chimney closely, you  see that the bricks go up around the tile liners of the flue. However, you need something at the top of the chimney to avoid snow or rain falling down around the tile liners. This is how the chimney crown will be very beneficial the most for the flue. It keeps the snow and rain out.

In this way, even the slightest crack found in the chimney crown can cause a serious issue in the flue. Most of the time, the cracks on the chimney crown are caused by the shifting of the chimney’s structure. Sometimes, the cracks are also caused by the shrinkage that might have begun since the first day the crown was installed. If there is a crack found on the flue, the water will easily go through it.

How to Fix It

Depending on how bad the leaky chimney is, the method used to repair the cracked crown will be different as well. In most cases, chimney crowns only have tiny cracks. However, you need to keep in mind that big cracks are often started from the smallest ones. In this way, no matter how small the crack is, make sure that you fix it soon.

You also need to know that both water thaws and freezes in small cracks can lead to big cracks after some time. Fortunately, there are some great crown coating materials that you can use to fix the problem. They will not only allow you to cover the masonry but also avoid tiny cracks becoming big.

But, what if the damages caused by the cracks on the chimney crown are serious? Well, the only possible way to repair the damages is by removing and relaying the masonry. Keep in mind that you can’t fix them only by covering the gushing wound with a bandage aid. You can’t even simply coat the damaged crown of the chimney and hope it will work.

Reason 3 – Condensation 

You need to know that a leak on chimneys from the inside out is commonly caused by condensation. It is very annoying since many methods can easily fail. Either it is flashing or a chimney cover, they can’t be used to fix the problem. Even rebuilding the entire top of the flue will not help much.

The leaks on chimneys caused by condensation might happen if a flue is converted from wood to gas burning. The condensation happens when the conversion is not fitted with the liner properly. Due to the improper installation of the liner and the lower temperatures, the gas fireplaces will give off fumes.

Most of the time, people do not check on leaks that occur in their attics on a regular basis. In this way, moisture in the attics would have been there for a long time until you realize it. Then, it will be too late for you once the moisture is noticed. Though there is only a moisture leaking found in the attic, it can spread to the entire house quickly. The longer you let this happen, the more money you need to repair the damages.

How to Fix It

Keep in mind that gas fumes can be low in temperature sometimes. Not only that but these gas fumes also come with a lot of moisture in them. They will condense on the inside of the chimney if it is too old or too large. The condensed gas fumes  easily soak the bricks. As the results, they will be kept moist all the time. You will need a chimney liner and some professionals can give you the help needed.

Reason 4 – Broken Chimney Flashing

The chimney flashing is needed to prevent water from running into the area where the structure of the bricks comes through the roof. Sometimes, it also avoids the water to go to the brick structure area that comes close to the roof. You need to know that there is often a quite large gap found between the roof and the bricks. If the gap is not sealed up properly, water will pour directly to the chimney from that hole.

If you suspect that your chimney flashing is leaking, you can try to look for signs of water damages in your attic or ceiling. You might need to have an inspection on your flue. One of the most common methods used to check on the chimney flashing is by running a hose around the place where your roof and chimney meet. Make sure that you check the inside of the flue for signs of moisture or water after running the hose for a few minutes.

Another common reason why chimney flashing damages is that there is not enough flashing put when the construction is started. It can also cause the leaky chimney.

Most of the time, chimney flashing is made of aluminum. It then runs in between a couple bricks.   The flashing chimney later bends and then goes on to the shingles’ top. Waterproof “stuff” is often used to seal these spots. Most of the time, the “stuff” chosen is tar even though it is not the best option either. In many cases, chimney flashing doesn’t last forever. As for the tar, it even lasts less than the chimney flashing.

How to Fix It

Fixing a leaky chimney caused by flashing can be very tricky. However, some materials in the market are known to be better options to seal the flashing now. You can do research or ask professionals to help you find the best sealing materials. A good material chosen for the flashing will not only work well on your chimney but also seals better and lasts longer.

Reason 5 – Leaking Bricks

Compared to previous reasons why chimneys leak, the leaking bricks are the worst cause. You need to know that both mortar and bricks pass water. However, just like the chimney crown, the thawing and freezing water during the winter can damage the chimney bricks and eventually leak into your house.

Even if you have heard about waterproofing a chimney, doing research will be very helpful. You need to be very careful in selecting the material used in the waterproofing. This is because the water will dry out after a while if it is absorbed into a mortar joint or a brick in the summertime. The only part of the chimney where water will not dry soon is the surface located in the shade or on the house’s side. This is because the two places rarely receive sunlight, making the walls stay wet for longer time than other areas.

The water will be easily trapped inside the bricks if you apply a waterproofing material that can block the pores of the mortar and the bricks physically. You need to know that some bricks can get soggy actually. However, most experts suggest that it is more likely that the water will just be absorbed into the house.

Applying silicone based-water sealant might trap the water. You need to be careful since it can cause more serious damages to the chimney. As an alternative, you can use polysiloxane type waterproofing agents to seal the leaking bricks.

How to Fix It

How to find a leak on a chimney caused by leaking bricks? Well, you need to check on the masonry surface. Then, you can do the Masonry Absorption Test (MAT). This is a test that tells you whether you need to waterproof the chimney or not. In conducting the test, you are required to attach a special test tube to the side of the chimney. Then, you have to record the time needed by the water to be absorbed into the walls.

Leaky Chimneys that Aren’t Chimney Leaks

Aside from the leaky chimney caused by the five factors mentioned previously, there is something uncommon but still possible to cause the leaks on a flue. You need to know that sometimes a leak can start in a different place. But, somehow, it later finds ways to your chimney. Then, the leak will enter the inside of the room visibly where the chimney is installed.

For instance, the roof of your house might have a leak through a roof shingle at the top. The leak might also happen on the attic vent. Then, the water goes above your ceiling or into the attic. Either it rolls along the stringer or drips to the floor, the water will find its ways to the flue.

If the stringer – a long piece of wood that makes the room out of your house roof trusses and then goes to the length of your living space – is un-level, water can easily travel and wind up in the flue. If this is the case, you might not find the leak until you spend a lot of money to fix everything else.

Another rare but a possible case of leaks on chimneys is that there is so much moisture in your attic. It will cause the moisture to condense and then roll down the stringer onto the flue. This is possible to happen if your attic receives a lot of humidity in it. For instance, instead of a vent, your dryer vented into the attic. The leak on the chimneys can also happen if your gas furnace just dumps into the attic even though you have vented it by using a B Vent.

Get Professional Help

To repair the leaky chimney, you will need help from those who have expertise in this area. To find the best service for your chimney, there are some things you need to consider well. Make sure that the quality offered is the best one. They should not only repair the leak on the chimneys but also avoid the same problem from happening again in the future. Not only that but they should also be highly responsive and the price offered is affordable.

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