How to Fill Cracks in a Brick Fireplace

If you own a fireplace in your home, it is always a smart move to inspect both the inside and outside areas before using it during the winter months. Upon examination, you may notice some cracks that have formed in the mortar joints between the bricks. Cracks can occur in the mortar over time, as well as from constant exposure to high heat. You don't need to have any masonry experience to repair these cracks, as there are caulking products that will quickly aid you in repairing the mortar joints.

Damp rag
Toothbrush
Clean rag
Caulking gun
Silicate-based refractory cement caulk

Instructions

- 1
  Examine the inner area of the fireplace for cracks. Look at the mortar joints between the bricks, as this is where most cracks will usually be located.
- 2
  Wipe the cracked area with a damp rag to remove any old soot and grime.
- 3
  Brush out the crack with an old toothbrush to remove any old crumbling mortar material.
- 4
  Wipe the crack clear with a clean rag.
- 5
  Load a tube of silicate-based refractory cement caulk into a caulking gun. This caulk is specifically designed to withstand high temperatures, up to 2,000 degrees Fahrenheit.
- 6
  Place the tip of the caulking gun above the crack and squeeze the trigger. Apply a bead of caulk no wider than 1/8 inch. Use multiple beads for larger cracks, rather than one larger bead. Wipe away any excess caulk with a damp rag. Allow the caulk to dry for the recommended amount of time as labeled on the product directions.
- 7
  Build a small fire in the fireplace. Try to keep the temperature below 212 degrees Fahrenheit, and let it burn for up to four hours. This will help the caulk set and cure properly.

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