How to Fix a Cracked Fire Box

Written By
James Clark
James Clark
Published: Sep 14, 2009
Updated: Nov 20, 2021
1 minute read

Water damage is also a possibility. You can make repairs to minor cracks and chinks in the masonry using supplies from your local hardware or home improvement store.

Things You Will Need

  • Fireclay or other heat-safe mortar compound available at hardware and home improvment stores.
  • Putty knife
  • Old rags
  • Flashlight
  • Old newspapers
  1. Lay sheets of old newspaper across your hearth to minimize mess.

  2. Empty the fireplace of all ash, burnt wood, and other debris. Then remove the log grate and set it aside.

  3. Clean the inside of the firebox with damp rags, scrubbing the interior walls and flooring where the log grate normally sets. Then allow it to dry completely.

  4. Inspect the firebox with a flashlight to note all cracks, loose masonry and chinks in the mortar.

  5. Use the putty knife to spread fireclay across damaged areas, and work the material deep into the cracks using the flat blade of the putty knife to apply pressure.

  6. Smooth out the fireclay for an even coat and uniform appearance.

  7. Allow the fresh mortar to dry for 48 hours before using the fireplace.

The Drip Cap

  • The fire box is the space inside your fireplace where wood combusts to release smoke up the chimney and spread warmth into your home.
  • Water damage is also a possibility.
  • Use the putty knife to spread fireclay across damaged areas, and work the material deep into the cracks using the flat blade of the putty knife to apply pressure.
James Clark

James Clark began his career in 1985. He has written about electronics, appliance repair and outdoor topics for a variety of publications and websites. He has more than four years of experience in appliance and electrical repairs. Clark…

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