6 Common Causes and Solutions for a Leaking Chimney

We’ve had a harsh Midwest winter this year. Snow and ice has covered roofs for weeks at a time. A leaking chimney is often a result of these severe weather conditions. What actually causes a chimney to leak?

There are many common causes for a leaking chimney. A professional roofer can help you determine why your chimney is leaking into the home or business and what can be done to eliminate this problem. One very common cause of this problem is that rain is getting into the top of the chimney, and then working its way into the home.

A chimney cap that has cracks in it can also be a reason for leaks that originate in the area of the chimney. These cracks allow moisture into spaces where it should not be. Condensation is another reason for many chimney leaks, because moisture cannot evaporate or escape and it is pulled downward by gravity.

If the chimney flue is uncovered then this could cause water to come in. Any missing or rusted flashing may not keep moisture away as intended. The bricks in your chimney may also allow leaking if they are not properly waterproofed, and the wrong waterproofing materials can be just as bad as not waterproofing the bricks at all.

1. A Leaking Chimney May be Caused by Rain Getting in at the Top

If you have a leaking chimney then a professional will usually check to see if you have a cover in place before checking anything else. If your chimney is not properly covered on top then rain may be able to fall directly into the opening, and this allows the water to travel into the structure. A chimney cover can fix this problem.

2. Cracks in a Chimney Crown can Cause Leaks

Another common cause of a leaking chimney is a cracked crown. As the material freezes and thaws or the structure shifts, this can create cracks, and water can easily slip through these cracks and cause leaks. The concrete may also shrink and gaps may appear. The cracks need to be filled in and repaired or the crown needs to be replaced to stop the leaking.

3. Condensation is Often the Culprit When a Chimney Leaks

Condensation inside the chimney can cause a leaking chimney. This is often a problem when the liner used is not the ideal size or material. Instead of allowing moisture to evaporate, the condensation may just soak the brick interior and then drip down. Usually a new liner will resolve this problem.

4. An Uncovered Flue can be a Source of Leaking at Times

A leaking chimney may be caused by an uncovered flue. But this is normally only the case when a metal chimney liner is used. The problem can normally be eliminated by covering the flue in order to prevent the leak from reoccurring.

In situations where oil or coal is burned, or when wood/pellets are used as primary source of heat, do not use aluminum or black-painted galvanized steel covers.

Source: HY-C Company

5. Flashing that is Rusted or Missing may let Water In

Flashing is an important component if you want to prevent a leaking chimney. This metal is used to direct water away from the opening where the chimney comes through the roof. If the flashing is rusted or missing, or if the sealant no longer seals the materials completely, then you could end up with water coming in where you do not want it.

Flashing is used to seal and protects joints in a building from water penetration by direct the flow of water away from these otherwise vulnerable areas. For Flashing to function properly it is important that it is installed correctly.

Source: GAF Flashing

6. Using the Wrong Material to Waterproof Bricks

Sometimes a leaking chimney is caused because the material used for waterproofing the bricks is not the right product. The waterproofing material should not block up the pores of the brick or block of the chimney, because this can prevent evaporation and cause water to build up. Applying a waterproofing product designed for chimney bricks will eliminate the cause of this type of leak.

Have you ever had a leaking chimney? If so what caused the leak and how did you fix it?