When you’ve got a chimney leak, there are many places it could be leaking from (there are a finite number of sources that can contribute to the problem). At Chimneys Plus, we believe in a thorough three-step process that we use for all leak inspections: 

  1. Investigate
  2. Plan
  3. Repair 


In this blog post, we will break down the investigation part of our three-step process.


If you know your chimney has a leak, look around both in the house and outside of it for any potential spots. 

  • Document the evidence of the leak. Is it ceiling damage, dripping water from the ceiling, dripping water in the fireplace, do you hear a dripping sound, is there discoloration of brick, or a white powder?
  • Do you see leak evidence in the attic? What about the timing of the leaks? When do you see it? Every time it rains? Only with heavy rains? Has it been getting worse? Has anyone tried to fix it? What did they do?
  • The more challenging the leak, the more details you collect, the better chance there is to locate the source(s).


Once we have identified the leak evidence, it’s time to get up on the roof and look for sources. It is always realistic to remind yourself that leak sources are not always obvious. Sometimes it takes trying one thing and then seeing what the results are. Sometimes it’s better to throw all your efforts into addressing all the possibilities at once rather than taking an incremental approach.

Sometimes the leak investigation process can include what we call a Live Leak Test where we get up on the roof with a hose and systematically spray water on the chimney to see if we can actually make the chimney leak. There are three main points of entry that could contribute to a chimney leak: 

1.The first main point of entry is through the chimney itself.

The most common cause of chimney leaks is due to what’s called a “sponge effect”. The chimney is made up of masonry, which is porous by nature. The chimney acts as a sponge and absorbs water. The more it rains, the more water it holds until it is completely saturated. The water eventually makes its way out of the masonry at a lower level – sometimes into your home.

This type of leak is often evidenced by white staining (efflorescence) on the outside of the brick. This staining is the result of evaporated water leaving behind salts and other minerals.

Another way the chimney itself could be the source is through cracks and gaps in the masonry or the mortar. Gravity and wind can direct rainwater into the cracks, and if enough accumulates, it will end up inside your home and potentially cause water damage.

Lastly, we often find that leaks come from chimneys that lack a sufficient cap, contain cracks in the crown (the very top of the chimney), or have a chimney chase that contains holes or holds pooling water. A concave chase that pools water may eventually develop holes that end up letting water dump into your chimney or house, causing water damage.

2.The next main point of water entry is through your roof.

While you’re in the investigation stage, it’s important to look for any possible shingles missing or other points of entry on your roof. We make sure to walk around the whole house looking up at the roof so we can see if there are any gaps between shingles before we get on the roof and examine it up there. 


If there’s a hole in your roof or in some shingles, water can get in underneath the shingles and make its way into your home. After you look for damaged or improperly installed shingles you can look for nearby roof interruptions such as plumbing vents, dormers, attic fans. Any time you have something coming out of your roof, there is a potential leak. 


In addition, if you have poor seals on your plumbing vents, that can accumulate water and spill into your home.  These roof leaks can even appear like it is coming from the chimney because water that gets underneath roof protection may run undetected to the nearest hole in your roof which in some cases is the chimney.


We’ve written extensively before about roof leaks and our investigation process for that. Click here to read our 3 unexpected causes of roof leaks blog post.

3.The final main point of entry is through the flashing.

The flashing is the barrier (often metal) that joins the chimney to the roof line. If there is a poor seal on the flashing, the water can sneak in between the flashing and the chimney or in between the flashing and the roof. Flashing can also develop perforations through which water can travel or it can simply be installed incorrectly causing leaks.  

You can check out our blog on Roof and Chimney Flashing here

diagram of chimney

If you aren’t sure on how to proceed once you’ve discovered there is a chimney leak, we recommend you ask yourself four questions:


  1. What are the potential consequences of this leak? 
  2. How aggressive do I need to be to get this leak fixed? 
  3. What are the likely sources of the leak? 
  4. What combination of leak sources are most likely contributing to the problem? 


Some homeowners may be very DIY and love a challenge such as investigating a water leak on your home but some homeowners would rather have an expert handle the problems.


If that’s the case, give us a call. We’ve got experts who can come out and walk you through each of these questions as well as the three-step process. We have a variety of options to help stop the leak, most of which come with a 10-15 year warranty and some even have a lifetime warranty! 


By working through our three-step process, you will come out with a plan to stop leaks in the future. In the majority of cases, the leak can be fixed with a long term no-leak prognosis. Flashing repair, repointing and cap replacement are often associated with holes that are letting water in. A much smaller percentage of water leak cases involving chimneys require ongoing leak management. Every few years you may need to reapply another treatment of waterproofing spray or caulk cracks that appear over time. Either way you have to understand sources and choose the best solutions. We strive to be the leader in comprehensive rainwater solutions, so reach out to us with any questions or if you need help fixing a chimney leak!