Reasons for Chimney Leaking in Brick Chimneys
Brick chimneys can leak for a variety of reasons. Bad or incorrect flashings and seals, defective construction, chimney liner issues can all cause a chimney to leak into the house.
Disclaimer:
These problems are meant to be examples of the common ways chimneys can leak from my past experiences. Any of these examples or none of these examples may apply to your chimney. Always contact a licensed chimney expert for your particular chimney leaking problems.
Bad or Incorrect Flashings
Chimney flashing is the metal that joins the roof to the chimney. It should be installed in a way that water runs down the flashing and is unable to get under the flashing, just like your roofing materials. Chimney flashings are typically made from a durable material, then often sealed with a flexible sealant such as tar, silicone, polyeurathane...etc.
One of the first things that can cause a...
Bad Chimney Crown or "Cap"
The chimney crown or "cap" as it is commonly referred to, is the mortar or concrete on top of the brick or stone that you see. if the crown or cap is cracked it will allow water to seep in behind the brick work. If the cap or crown is made from mortar, it can be even worse. Mortar does not repel water by default, instead it can absorb water, which again will leak into the chimney structure. The water that is in the chimney structure is subject to gravity. Water works its way down through the masonry and can eventually work its way into the house....
Lack of a Chimney Rain Cap
Many times the flue tile that exits out of the top of the chimney does not have a cover on it to protect it from rain and animals. When the flue does not have a cover on it, it allows water to drop drown to the base of the chimney in the case of a heating appliance flue. In the case of a fireplace, water drops down to the smoke shelf of the fireplace. The water can then pass through the masonry and deteriorate the back wall of the fireplace or the base of the chimney. Many times the first sign of water deterioration is called efflorescence...
Chimney Leaking From The Inside
Chimneys can leak from the inside out as well. When you burn a gas appliance, water is produced by the combustion process. In a properly sized vent or chimney, this water is in the form of steam. The draft of the chimney takes the steam up and out of the chimney. Chimney leaking problems can arise when the chimney is NOT the right size for the appliances using it. When the chimney is too big for the appliance(s)...
Bad or Deteriorated Mortar Joints or Brick
One of the most pesky ways a chimney will leak is through the mortar joints or brick/stone/block. When the chimney exterior has bad or damaged masonry, water can enter in through the holes or cracks in the joints. When sufficient water has entered in, gravity takes over and pulls the water down through the chimney...
The Mystery Leak
This type of leak is one of the hardest to find and/or diagnose. Imagine this scenario.. You have a leak in the chimney, but it only leaks after it has been raining for a long period of time, or heavy rains, or even short windy rains.. You have checked the flashings, they are good. You have checked the concrete cap, it is good. You have checked the brick and mortar and it appears to have no holes or ways for water to get in. "What is going on?" you might ask yourself. Everything appears to be good with the chimney. Every year people spend a ton of money trying to diagnose these types of leaks. This type of leak usually (not always) boils down to the following: ...
