Benefits of Chimney Waterproofing 

One of the scariest phrases a homeowner can hear is “water damage.”  Most of the time water damage is associated with roofs, rotten wood, basements, or failed water pipes.  Did you know chimneys are also susceptible to water damage?  When damaged, the impact can extend far beyond the chimney’s structure! As ironic as it sounds, damage caused by moisture can make chimneys more susceptible to chimney fires and even house fires.

chimney lining

In the basic structure of a masonry chimney, water has four potential access points.  These are located at the top or flue, through deteriorating mortar joints, through bricks, and where the chimney meets the roof.  If neglected, damage to one or more of these structures can lead to rusted and deteriorating metal chimney components, cracked mortar and bricks, rotting of wood adjacent to the chimney, roof leaks, deterioration of the flue lining, and ultimately, a structural collapse of the chimney. Properly protecting and waterproofing your chimney are important for the longevity of your chimney and the surrounding structures.

At each potential points of entry for water and moisture, waterproofing precautions should be taken.  By taking a preventative approach before serious issues arise can end up saving you thousands of dollars in expensive repairs later on.


An uncapped chimney grants water, snow, and moisture direct access to the flue and other components of your chimney’s interior.  This can lead to deterioration of the flue, damper, and even the interior of your home.  Weather events like high wind and heavy rain can also be damaging.  A chimney cap (also referred to as a “rain-cover”) provides a basic and inexpensive fix.  As an added bonus, chimney caps can prevent critters, leaves, and debris from creating hazardous blockages in the chimney.

A chimney crown protects and seals the top of the chimney from the flue liner to the chimney’s edge.  A proper chimney cap will direct water away from the flue and prevent water from the bricks and mortar on the vertical exterior of the chimney.  Many chimney caps are built using traditional mortar, which is highly porous and prone to cracking.  Instead, the cap should be constructed using a cement-based mixture to better prevent moisture penetration.

Mortar Joints

Deteriorating mortar joints create easy access for water.  Freeze and thaw cycles cause mortar to expand and contract.  In time, the mortar will crack or flake.   Mortar is the glue that holds a brick or stone chimney structure together.  If neglected for a long enough period, the entire chimney can eventually collapse.   “Tuck-pointing” or “re-pointing” damaged mortar removes these damaged points of entry and replaces it with good mortar.  Periodic tuck-pointing dramatically extends the life of your chimney, not to mention improving the aesthetic appearance.


Bricks and other masonry materials are extremely porous.  In their natural state, brick or defective mortar joints absorb water like a sponge.  The moisture is then wicked to the chimney’s interior structure with use, deteriorating both the mortar and bricks more quickly.  This shortens the chimney’s lifespan and ultimately, leads to structural collapse. Masonry waterproofing systems prevent moisture from entering through the exterior while still being breathable.  Applying a waterproofing product won’t address existing damage, but it will provide a preventative measure that inexpensively extends the life of your chimney.

Where the Chimney & Roof Meet

Where the chimney and roof meet can be a problematic area for your chimney, roof, and structure of your home.  These joints provide ample opportunity for water access if not properly sealed.  The resulting leaks can damage surrounding wood, ceilings, chimney structure, wooden rafters, and more!  Properly installed and maintained flashing provides a waterproof seal between the roof and the chimney.  Flashing is designed to allow the differing materials used in roofing and chimney construction to expand and contract at their respective rates while maintaining a watertight seal.  Flashing is a very important component of a waterproof chimney and should be regularly inspected and repaired as needed.

Protecting your chimney from water and moisture is an important and often neglected aspect of home maintenance.  If ignored, the resulting water damage can be very costly and extend far beyond the chimney itself.

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