Chimney Leaks: Why They Occur, and How to Stop Them

Chimney Repair - Masonry ContractorHave you noticed water coming into your home through your roof or chimney? Homeowners generally notice leaks during periods of significant rainfall, like flash floods or hurricanes. Knowing the cause of your leak can make your chimney repair much easier, and save you the time and money associated with extensive water damage. Today, we’ll introduce you to some of the most common causes of chimney leaks.

Uncovered Chimneys

The simplest reason for chimney leaks is one of the most common: water entering the chimney directly from above. Luckily, the solution for this is simple: install a chimney cover. Chimney covers can prevent rainfall from coming down the top of your chimney, as well as form a barrier to keep out birds, squirrels, and other pests. The cover also acts as a filter to keep other types of debris from clogging your flue, which reduces the risk of buildup and carbon monoxide poisoning.


Chimney flashing is the material that prevents water from entering at the point where the chimney and the roof meet. Generally, the flashing is made of aluminum, copper, steel, or vinyl/PVC. Leaks often occur at the chimney when flashing fails. Damaged flashing can be cemented or patched; however, it is likely that a major leak may need to have the flashing replaced completely. The use of tar instead of traditional flashing can also cause leaks. Luckily, this can be remedied by installing proper chimney flashing on your home.

Cracks in the Chimney Crown

The chimney crown is the cement part on top of the chimney. Its very purpose is to keep rain out. Naturally, when your crown has cracks, the water seeps through the crown, and into your home. Most crowns have some small cracks.  However, repairing the small cracks is just as important as fixing the large one. Weather damage, as well as freeze-thaw cycles will eventually cause small cracks to grow. Crown coating materials can cover the masonry and prevent these small cracks from becoming a real problem. However, if the cracks in your chimney are already significant, the only fix is to completely relay the masonry. Coating materials can prevent damage from small cracks, but large cracks are no match.

Leaking Bricks or Stones

Bricks and mortar both pass water, and often large amounts. The problem with masonry units is the same as with a chimney crown: erosion and freeze-thaw cycles can cause damage that leads to leaks in the house. A good preventative measure to help keep your chimney dry is a waterproofing solution. However, as is the case with chimney crowns, some cracks may be too far gone to simply coat the chimney. In this case, the best solution is to replace cracked bricks or stone, or to repoint cracked mortar in between that is causing the leak.

Obviously, prevention is the best course of action when it comes to preserving the lifetime of your chimney. Installing a chimney cover, and coating your chimney with waterproof materials can keep moisture out for a long time. However, if your chimney does spring a leak, knowing the source of the problem will make chimney repairs quicker, more effective, and hassle-free!