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The Major Causes of Chimney Leaks


If you have an older brick chimney, a leaky chimney can lead to long list of other problems.The main cause of chimney leaks is water falling straight into your chimney. If your chimney doesn’t have a chimney cap or cover, much of the rainfall will find its way into your chimney and eventually into your fireplace. Creosote or residue buildup left over from burning wood in your fireplace can drip down the chimney and into your living room. 

In some cases water penetrates the interior of the chimney or through a crack and it runs down the flue or the brickwork inside the house or attic. Chipped or cracked bricks expose the chimney’s brickwork dampening the surface of the brick and forming white lime deposits on the exterior of the chimney.

If it makes you feel better, you’re not the only one with this problem. Over time, chimneys that are exposed to the elements such as wind, rain, sleet and snow, crack and chip. The mortar that holds the chimney together loosens. The flashing around the chimney gets worn, corroded or due to inadequate coverage because of improper installation allows water to penetrate the chimney structure. I have seen chimney flashing that had been glued to the brick rather than sealed with silicone.  Branches and debris can force their way under the chimney flashing.  Different types of flashing have different life spans. Aluminum flashing can rust in 5 years while copper flashing will usually last 20+ years. Lead flashing can last over years.

A chimney crown covers the top of the chimney and is made of concrete. Because a chimney is built from the ground up and it deteriorates from the top down because of its direct exposure to the rain. While most crown failures were due to the bad craftsmanship in many cases the crown wasn’t sealed correctly. A cracked chimney crown can cost almost $1,000 to repair but if left untreated it can cost you upward of $3,000 in the long run.

In some cases water buildup or condensation in the interior of the chimney can also cause chimneys to leak. If a chimney lining hasn’t been installed correctly or if it’s the wrong size then bricks will be exposed, creating moisture from the fireplace. After the fire has been extinguished, the moisture will leak down the chimney with the creosote buildup. 

The other aspect that you have to take into consideration is the chimney’s positioning. If the direction of the water runs directly into the chimney then you should install a chimney cricket in the back of the chimney.  A cricket looks like a saddle and is designed to divert water on a roof around the high side of a chimney or the transition from one roof area to another, the cricket is normally the same pitch as the rest of the roof, but not always.

There are many causes of chimney leaks. A trick to determining where the leak is coming from is by running a hose down the chimney and identifying the trouble areas.

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