Causes of a Leaking Chimney

Many people only think about their home’s chimney when the weather begins to cool and toasty fires become appealing. In fact, as hardy as a chimney may be, it needs maintenance too. Worn mortar, chimney crown or cap problems, and loose or rusted flashings can all affect whether your chimney can keep water out of your home. A chimney water leak can easily lead to water damage problems.

Chimney Water Leak Causes

The first thing you’ll need to do when you find a chimney water leak is to identify exactly where it’s coming from. There are several potential water intrusion points, and in some cases water may be entering your home from a combination of problems.

Here are some common causes of water leaks in chimneys:

Chimney water leakWorn or Eroded Mortar Between Bricks
Mortar is what binds brick chimneys together and keeps them from falling to pieces. It’s a fairly durable substance, but not nearly as durable as brick and wears out over time.

When mortar wears away, it allows water to enter the chimney more freely. You can fix this problem by patching these problem spots.

Problems with Flashings
Chimney flashings are pieces of metal which sit on the juncture between the roof and the chimney. They direct water away from the small gap and towards gutters instead. Flashings can last for several years, but improperly installed flashings or damage from storms can reduce their lifespan.

Chimney leaks caused by problems with flashings can easily be fixed by replacing the flashings.

Worn or Broken Chimney Crown
A chimney crown is a slightly sloped piece of concrete that surrounds the flue, acts as a cap for the bricks, and sits just below the chimney cap. Chimney crowns can crack with age or use. They can also become separated from the flue in some cases, such as poor construction, natural structure changes, or cement shrinkage in old chimney crowns.

Small cracks can easily be fixed with chimney crown coating materials. Larger cracks or damage to the chimney crown may require professional replacement.

Broken or Missing Chimney Cap
Chimney water leakMuch like the name suggests, a chimney cap is a protective cover that sits at the top of the chimney. It is designed to have an overhanging lip and a mesh grate that allows smoke out while preventing debris, animals, and water from entering.

Heavy storms, debris, and wind damage are all potential causes of damage to a chimney cap. A broken chimney cap may feature a crack or missing panel that allows water inside. A missing chimney cap essentially allows anything and everything to enter the home. Replacing a chimney cap will prevent the chimney from leaking.

What is Chimney Waterproofing?

Chimney water leakWaterproofing bricks and mortar is a great way to keep water out of a chimney. Some homeowners may not be comfortable with spending a weekend on their roof, in which case they should call a professional chimney repair service.

For homeowners who are confident in their roof walking abilities, chimney waterproofing is a DIY weekend project.

You will need:

  • Power washer or chemical chimney cleaner
  • Stiff bristle brush
  • Mortar repair
  • Chimney water repellent
  • Drop cloths



  • Clean your chimney using a power washer or a chemical chimney cleaner plus stiff bristle brush. This step will help you apply waterproofing evenly on the bricks.
  • Repair any minor cracks you find in the mortar using a tube of mortar repair. Let the mortar dry according to the manufacturer directions.
  • Place drop cloths to protect roof shingles.
  • Apply the chimney water repellent starting from the bottom and working your way up. A pumping garden sprayer is ideal for this step, as you’ll want to apply a coat thick enough to start running down the sides of the bricks. This ‘flood coat’ will absorb into the bricks and extend the life of the waterproofing.

It’s important to note that you should not use a sealant on your chimney. Sealants trap water inside of bricks and can cause long-term damage. Waterproofing, on the other hand, keeps water out while allowing the bricks to dry naturally. Be sure to avoid silicone-based waterproofing materials, as these can trap water inside masonry.

Tidal Wave Response

If your chimney has leaked water into your home, call Tidal Wave Response! We are happy to assess the damage to your home and provide top-notch water damage restorations.

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