Water is the enemy of masonry.
As rain pummels bricks, stones, and mortar, it gradually seeps into the substance. While masonry appears to be solid, it actually has tiny spaces that allow rain water to enter. One of the first visible signs of a water penetration problem is spalling, which is the flaking off of the exterior surface of bricks or stones. By the time spelling is visible, it is too late because water is already inside the bricks.
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.
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.
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.
The method of application is critical to the performance of the water repellant as well as the type used. The sealer will stop further water penetration, however.