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Chimney Leaks

Q: Water comes out of the chimney cleanout in our basement every time it rains, but we can’t figure out where it is coming from. How does water get inside a brick chimney and what can we do to stop it?

A: Most people would be surprised to know that Nova Scotia gets an average precipitation of 1,388mm per year – which equates to over 54 inches of water hitting the ground, roof and chimney each year; so keeping water or excessive moisture out of our homes can be a constant battle.

When it comes to typical penetrations of the roofing system, the chimney offers the most opportunities for water to make its way into the home. Here is an example of the four common causes of chimney related leaks:

Chimney Leaks

1. Rain Cap
Flue pipes come in many sizes, but 8”x8” or 8”x12” clay liners are typical – which is a very large opening for water to get inside. If rain is allowed to freely flow down an open flue pipe, it will mix with soot or creosote and can create unsightly stains. A properly designed rain cap will not only minimize water entry, but it can help keep leaves and critters out.

2. Masonry Cap or Crown
The chimney cap or crown is a cement cover that is placed on top of the masonry chimney in an effort to shield the top of the bricks from the elements. A properly designed masonry cap should overhang each side by at least 2” and should gently slope away from the clay liner. Visible cracks or a poorly designed masonry cap could allow water in.

3. Deteriorated Mortar/Brick
The mortar between the brick will naturally deteriorate over time and will eventually need repointing. Repointing is the process of replacing the old mortar with new. Any visible gaps or cracks in the mortar will allow water to enter these voids and can cause significant damage through multiple freeze / thaw cycles.

4. Flashing Failure
Chimney flashing is designed to prevent water intrusion from where the chimney passes through the roof. Visible signs of excessive tar cover usually suggests past problems with leaks and non-professional installation. Sometimes the best place to inspect for flashing failure is from inside the attic space.

The inspection of a masonry chimney is part of a typical home inspection, but once they take possession of their new home most homeowners never think about regular chimney maintenance. Each year your masonry chimney should be inspected by a qualified masonry contractor. And if there are any wood burning stoves or fireplaces attached to the chimney, then it should be cleaned and inspected by a WETT Certified Chimney Sweep.

Lawrence Englehart (Global Property Inspections) is a Registered Home Inspector and be reached at or or