How Water Causes Damage to Your Masonry Chimney

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People don’t generally think of concrete and brick as porous materials, but they are. Water breaks them down into their base elements and causes a lot of damage over time. Waterproofing the chimney on a regular basis is the only real way to prevent damage. Repair damage as quickly as possible and use preventative measures to protect the chimney from future damage. Let’s look at how water causes damage to your masonry chimney.

Freeze and Thaw Cycle

Water inherently takes the path of least resistance. When it hits the masonry on your fireplace, it runs down toward the roof, usually in the same pattern. This pattern becomes the path of least resistance and the exposed masonry begins to pull water into it. Water from spring and summer storms may still be present when freezing weather hits if the chimney isn’t properly waterproofed.

Freezing water expands. When this water is trapped within masonry, it expands and often cracks brick or concrete. Warm weather or heat from the fireplace can thaw the ice, but the moment it freezes again, more cracking occurs. This may become evident in the spalling of brick or noticeable cracks in stone or brick masonry chimneys.

Waterproofing the Chimney

Waterproofing the chimney is the best way to save it from water damage. Most waterproofing materials are either sprayed or brushed onto the chimney. They may darken the masonry, giving it a very subtle shine or making it look brand new all over again. They allow water vapors to escape while preventing additional water from penetrating the masonry.

Signs of Water Damage

  • Water Stains – water stains may appear white or as dark stains that look as if something has been spilled down the chimney.
  • Rust – look for rust on the exterior of the chimney flashing and roofing as well as inside the firebox in the fireplace.
  • Decayed Mortar – mortar that chips out easily or is deeper than it should be needs to be repaired as soon as possible.
  • Brick Spalling – spalling bricks are a sure sign of water damage. If the spalling goes too far, the entire brick structure will become compromised.
  • Rotting Wood – the wood inside the roof will take damage and become structurally unstable if water damage is ignored for too long. Look for signs of moisture around the area where the chimney exits the roof.

All water damage should be addressed as quickly as possible to prevent structural instability in the chimney. You may be able to identify certain types of damage without calling in a certified chimney sweep, but don’t leave chimney repair to an untrained eye.

August is just around the corner, which means fall is quickly approaching. Many homeowners enjoy lighting the fireplace in the morning to knock the chill out of the air and then at night to take away the chill of fall. Make sure to have your chimney inspected, repaired, and cleaned before you light that first fire this year.

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