How to Seal Cracks in a Brick Fireplace Mantel

What You'll Need
Brick chisel
Wire brush
Brick mortar
Mortar coloring
Small bucket
Stir stick
Sharp trowel
Cement paint
Paint brush
Sandpaper, 400-grit
Spray bottle

A brick fireplace lends a warm and natural touch to any home. Brick has traditionally been the material of choice for fireplace construction. This is partly because it has an excellent resistance to heat and is easy to install. Brick is also one of the more affordable materials for a fireplace mantel. In the course of time, cracks may appear in your brick mantel. If you have some time to spare, this can be fixed with some basic materials.

Step 1 – Inspect the Brick Fireplace

Take some time to carefully check the condition of your fireplace. Note the location and nature of all cracks. Small cracks can be repaired as outlined in the steps that follow. However, for cracks that are extensive and run deep, it is best to consult a qualified professional. The damage could indicate some other structural problems which are best checked out by a professional.

Step 2 – Remove Mortar and Loose Brick

The crack may appear along the grout lines or run through a brick. Use a brick chisel to remove mortar and loose brick from the crack. Be careful not to damage the brick as you clear the debris. Clear away loose debris and dirt from the crack with a wire brush.

Step 3 – Clean with Air

Clean out the crack with some air. Use your vacuum or hair dryer set on “Cool” for this.

Step 4 – Prepare Mortar

Be sure to obtain a mortar which matches yours. Mix some mortar in a small bucket to seal the crack. Use a stir stick to mix until the mortar has a uniform color appearance and consistency. It is a good idea to allow a small amount of mortar to dry first before you seal. Dab a small amount onto a cardboard and allow it to dry. This will let you know if the color matches exactly. Add mortar coloring to the brick mortar until you get the desired shade. An exact match helps to give your fireplace mantel a uniform appearance.

Step 5 – Seal the Crack

Scoop some mortar with a sharp trowel and fill the crack. Take just a bit of the mortar so that you can fit it deep into the crack. Work your way up until the entire crack is fully sealed with mortar. Allow 24 hours for the mortar to fully dry.

Step 6 – Smoothen

Use a piece of sandpaper to smoothen the sealed crack. Work along the entire crack. Wipe away loose debris with a damp rag. Allow the sealed crack to dry. Over the next few days, spray waster lightly over the sealed crack to help cure it. You can do so about 3 times daily for the next 4 days. Allow the brick to dry for 24 hours before you paint.

Step 7 - Finishing

You may want to paint the sealed crack so that it matches the surrounding brick. Apply a cement paint of the same color as the brick mantelpiece with a paint brush.


  • Wear safety goggles to protect your eyes from airborne loose brick and mortar.
  • A dust mask helps to prevent inhalation of the loose debris.