Chimney Crown Repair: Why it’s Important

A chimney crown is a slab of material, usually concrete, that covers the entire top of a chimney, protecting the bricks below it and the interior spaces of the chimney structure. Crowns are prone to cracking over time, and when this happens, serious damage to the chimney could result.

Chimney Sweep Inc. of Lakeside, CA, repairs and rebuilds a lot of chimney crowns for our Southern California customers. Here are some things you should know about chimney crowns and the chimney crown repair process.

Construction of the crown

All types of chimney crowns cover the top opening of the chimney, minus the flue pipe. When built properly, the crown will be angled slightly down from the flue opening to allow rain to run off it rather than pool up on it.

A good safety feature in some styles of chimney crown construction is an overhang extending beyond the sides of the chimney. This causes water to fall off the crown and away from the vulnerable bricks and mortar of the chimney.

A properly built crown will protect the chimney system from incoming rain and debris.

What causes cracks in a chimney crown?

Extremely cold weather and the resulting freeze-thaw cycles can damage a chimney crown. In milder-weather regions, other things can negatively affect the crown and its stability, including:

Inferior materials used in the construction of the crown
Poor construction practices
Lightning strikes
Major chimney fires
Old age
Pounding hail storms
Earthquakes
Intense Summer Heat
Rain & Moisture

Damage resulting from a compromised chimney crown

It’s never good when water or debris can get into the interior areas of a chimney system. A cracked or deteriorated chimney crown can lead to:

Chimney liner damage
Ongoing masonry damage
Mold growth
Structural weakness

Not being aware of chimney crown damage or ignoring it can end up costing you thousands on major chimney repairs for the above and other problems that could have been avoided.

How to address damage to a chimney crown

Resolving chimney crown issues starts with an inspection. Your inspector will look closely at the crown to determine the extent of the damage. He or she will also inspect other areas of the chimney system if collateral damage is suspected.

There are several strategies for addressing cracks or deterioration in a chimney crown:

Crack repair

This involves scraping away crumbling areas in and around the cracks and then patching the gaps with a quick-setting repair mortar. Crack repair is a good option when deterioration is minimal or moderate.

Chimney crown rebuilding

When severe crown damage exists, the only option is to rebuild the entire structure from scratch. When built properly with quality materials, your new crown will serve you for many years.

Sealing the crown

Once the crown is repaired or rebuilt, it should be treated with CrownSeal or a similar product. CrownSeal creates a strong water barrier that’s flexible and won’t break should the materials beneath it shift.