A chimney fire can cause more damage than expected to masonry chimneys

Chimney fires are all too common, and often go unnoticed by the homeowner at the time of the event.

According to a recent poll by the Midwest Chimney Safety Council, and average of 1.5 fire-damaged chimneys are found every day that a chimney sweep works if he/she usually sweeps four to six chimneys per day. The number of damaged chimneys that homeowners are unaware of is staggering.

In the Kansas City area alone with 2.5 million people, there are a minimum of 25 full-time chimney sweeps working five days per week. Do the math figuring 48 work weeks per year and that calculates to 9,000 chimneys found with damages every year in one metropolitan area alone. That is a lot of chimney fires.

Masonry chimneys are designed to contain a chimney fire in order to keep it from spreading to the rest of the home, that is-- if it is constructed properly with the right clearances.

However, once a chimney has been damaged, often with internal damages that are not readily accessible, a second chimney fire is more likely to escape the masonry structure due to gaps created by cracks in mortar and bricks.

Another thing to consider is that masonry, while sturdy and solid, is not impervious to damage by fire, water, creosote, or moisture. Once a chimney is damaged by fire, water will likely leak inside and cause further damage and faster deterioration of the structure. The bricks and mortar may wash out, dampers rust, metal fireplaces rust, internal mortar joints between flue tiles may deteriorate, and often the back wall of a masonry fireplace shows water damage.

In addition to checking the flue, smoke chamber, and damper, the chimney sweep should check the facial wall of the fireplace for fresh breaks that can be caused by expansion due to heat in the smoke chamber area.

The smoke chamber is the place where most chimney fires start. Secondarily, the sweep should check all four sides of the chimney in all accessible areas including the attic for fresh breaks caused by expansion. Breaks can be minor or major, but may be related to a chimney fire.

In the photo example a chimney fire damaged the internal flue and smoke chamber, as well as the back of the exterior chimney. This area was not visible from the ground and the homeowner had no idea there was so much damage. The chimney was in good condition two years prior as noted in a chimney sweep’s evaluation except for the cement crown, which was deteriorating prior to the fire. A chimney fire occurred, and heat caused the bricks and mortar to expand outward, breaking mortar bonds between bricks and mortar and detaching the cement crown, causing cracks in the crown as well. Since it went unnoticed for a year, rain water further damaged the area as well as the internal part of the structure.

Homeowner’s insurance covers damage by chimney fire, but it is best to avoid a fire in the first place.

For these reasons it is imperative that all chimneys, including masonry chimneys, be inspected by a professional chimney sweep at least once per year. The sweep will sweep out the flue and smoke chamber, then inspect the chimney.

A Level II Inspection with a chimney camera is the best type of inspection to get because it allows the sweep to do a thorough inspection of the entire flue. It is also important to have the top portion of the exterior chimney examined if it is accessible. 

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