Using caulk gun to insert refractory mortar between the fireplace bricks
Steps // How to Repoint a Brick Fireplace
1 ×

Wash the Brick

 
Step One // How to Repoint a Brick Fireplace

Wash the Brick

Mark Schaub cleaning inside brick fireplace
Photo by Wendell T. Webber

Schaub dons nitrile gloves, then thoroughly scrubs soot off the sides of the firebox with an abrasive pad on a wet sponge. Soot dissolves fairly easily when wet. The washing also dampens the brick and mortar, a necessary step before repointing. 

 
2 ×

Dig Out the Loose Mortar

 
Step Two // How to Repoint a Brick Fireplace

Dig Out the Loose Mortar

Digging out old mortar in a fireplace
Photo by Wendell T. Webber

Using a grout-removal tool fitted with a triangular carbide blade, like the one made by Goldblatt, Schaub scrapes out cracked, loose, and crumbling mortar. He stops when the sides of the blade touch the edges of the brick. The blade’s triangular shape prevents it from going too deep (more than half the width of the joint). He then cleans the joints with a narrow, stiff-bristle scrub brush and sweeps up the mortar crumbs with a wet/dry vac.

 
3 ×

Wet the Joints

 
Step Three // How to Repoint a Brick Fireplace

Wet the Joints

Using a paintbrush to dampen mortar inside fireplace
Photo by Wendell T. Webber

Schaub goes over all the scraped joints with a nylon paintbrush, which he dips repeatedly into a bucket of clean water. Refractory mortar bonds best to a damp surface, and the brush bristles ensure that all the old brick and mortar are moistened. 

 
4 ×

Caulk the Joints

 
Step Four // How to Repoint a Brick Fireplace

Caulk the Joints

Using caulk gun to insert refractory mortar between the fireplace bricks
Photo by Wendell T. Webber

After slipping a tube of refractory mortar into a caulk gun, Schaub drags the tube’s nozzle over all the scraped mortar joints, leaving behind a fat bead of caulk. He also makes sure to fill any gaps between the hearth and the firebox floor.

 
5 ×

Pack the Mortar

 
Step Five // How to Repoint a Brick Fireplace

Pack the Mortar

Using a trowel to pack mortar between the fireplace bricks
Photo by Wendell T. Webber

Schaub uses a 3⁄8-inch-wide tuck-pointing trowel to smooth and press the soft mortar firmly into each of the joints, then scrapes off the excess with the trowel’s edge. In corners, a gloved finger performs the packing and smoothing functions.

 
6 ×

Wipe Away the Residue

 
Step Six // How to Repoint a Brick Fireplace

Wipe Away the Residue

Sponging away mortar residue from fireplace bricks
Photo by Wendell T. Webber

Multiple swipes with a damp sponge remove most of the mortar residue. Schaub will wipe the brick again in 24 hours, after the remaining residue dries to a haze. This mortar’s heat-resistant qualities kick in when it reaches 500 degrees. Either a heat gun or a small, brief fire will serve that purpose.

 
 

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.