Properly maintaining your concrete chimney crown prevents water from damaging the exterior and interior of your chimney. Chimney crowns come in a variety of sizes, but it’s generally recommended that a crown be at least 3” thick with at least 1.5”-2” of overhang or kerf to ensure structural integrity. The overhang prevents rainwater from running down the exterior brickwork. This protects your chimney and reduces premature brick and mortar erosion, cracking, and deeper water penetration.
A cracked or damaged concrete chimney crown can allow water to infiltrate the interior of your chimney chase, flue, and firebox. Moisture entering your chimney’s brickwork leads to cracks, leaks, and general deterioration. In extreme cases enough water may enter your chimney to create puddles on your basement or living room floor (depending on whether your chase is connected to your furnace or fireplace flue pipes). Water penetration can also create efflorescence. Efflorescence is a white salty residue that may become visible on your brickwork or chimney if it’s oversaturated with moisture.
Promptly repairing a concrete chimney crown is also a matter of safety. Chipping, cracking, or crumbling of the crown can cause concrete, mortar, or bricks to fall off the chimney which might injure people or damage objects below.
Repairing your chimney chase, flue pipes, firebox, and general brickwork can be costly. A healthy and well-maintained chimney crown can prevent a lot of these issues. Fixing or replacing a concrete chimney crown before significant problems develop is a relatively inexpensive and very cost-effective way of preventing more extensive damage. Next time you’re outside your home or building, take time to inspect your concrete chimney crown. Identify and professionally address concrete crown damage early to protect your chimney and prevent larger and costlier future repairs.