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The Importance of Repairing Fireplace Cracks!

Published April 2nd, 2018 by Guaranteed Property Inspections LLC

After conducting a few home inspections this past month I began to start noticing a pattern. Upon inspecting the fireplace two major issues stood out in each home I inspected:

  1. High heat caulking was missing at the gas line.
  2. Cracks at the firebox within the fire place.

Both of these defects pose a severe hazard. This condition can result in excessive heat entering the surrounding wall which poses as a fire hazard. Your fireplace comprises of three parts: the firebox assembly or combustion chamber, the fireplace opening and the hearth. If you spot a cracked brick or mortar along the firebox walls or interior chimney lining, it must be repaired immediately. The NFPA ranks cracks or other signs of deterioration within the firebox assembly as a fire hazard. Cracks are sometimes caused by mortar joints that may be too wide, allowing oily deposits called creosote to wedge inside and behind these narrow openings. Creosote buildup may also form along the firebox walls. As a result, flying sparks can re-ignite creosote and cause deadly fire outbreaks. The NFPA lists creosote buildup as the No. 1 cause of chimney fires.

Here are a few solutions to consider:

If you have a firebrick fireplace, use mortar high in calcium and lime in motor joints no larger than 0.25 inch. Apply fireclay mortar, which has a high fire resistance and can result in joints 0.125 inch in width or less. Portland cement can also be used to patch up cracks. Carefully chisel out cracked mortar in the firebox, and shape thin strips of fresh mortar into the joints. Avoid smearing or applying cement or fireclay over old mortar. Surface-coated or smeared mortar will likely not stick to the fireplace’s sooty surface. Back walls with broken bricks should be rebuilt with new fireclay or firebrick material.


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