Chimney Corbels

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February 13, 2020

What are chimney corbels?

Often called “shoulder” or “hips”, chimney corbels are bump-outs or protrusions on a chimney, most often found near the smoke chamber of a chimney. The corbels will follow the contour of your smoke chamber, which is shaped like an upside-down funnel. Without these corbels, your chimney would be the same width from the bottom to the top, and there would be a lot of unnecessary space and materials used in the construction of your chimney.

A chimney corbel that is covered by a concrete slab.
This chimney has a slab set over the corbels to protect it from water damage.

Not all chimneys have corbels. Some have only 1. The thing that determines how many corbels your chimney has is typically related to how many flues your chimney has. For example, my chimney has a corbel only one 1 side, as I have a fireplace on the main floor, and another in the basement.

Corbels Need Special Care

Chimney corbels need to allow water to shed off the surface. They need to be sloped and smooth to do this. If your chimney was built with brick holes facing upward, they can retain water which will cause damage to your chimney after the freeze-thaw cycle. For these types of builds, we recommend having the corbels capped, whereby we put a concrete slab over the bricks, which allows water to run off without entering the bricks below.

A chimney with a square corbel.
Water will pool on top of this square corbel and will eventually cause damage to the chimney.

If your corbels are stair-stepped but do not have the holes exposed, they are still at some risk because water will pool on any horizontal surfaces. For these, we can smoot out the stair-step with a mortar fill.

A damaged chimney corbel that needs to be repaired.
This stair-step corbel is a very common design, but it needs better protection. Note the spalling and vegetation growing. Someone attempted to run a mortar bead to help shed water, but it was too little too late.

Even if your chimney is constructed in such a way so that the brick faces are sloping the water away, you will want your chimney sweep to inspect them annually to ensure water is not beginning to penetrate the mortar joints.

If your chimney has corbels, ask your sweep to let you know how it is doing during your next inspection.

Written By Steve May

Steve May founded Chimney Works And Rocky Mountain Stoves in October of 2001. Steve is an entrepreneur at heart, and avid outdoorsman, and a proud father of 5.

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