How to Repair a Refractory Brick in a Fireplace

Clean the fireplace and inspect the firebox closely. If the bricks and mortar are not clearly visible, use a stiff-bristled brush and, if necessary, a fireplace cleaner to remove soot buildup.

Remove any damaged or loose bricks. Use a screwdriver to lightly scrape the joints between bricks to check for loose mortar.

Scrape old mortar off of fully intact bricks that have been removed from the firebox. Use a stone or masonry chisel and stiff brush to remove old mortar from the brick. If the brick is solid and in good condition, it can be reused. A broken or crumbling brick should be replaced.

Remove old mortar from the bricks surrounding the removed bricks.

Prepare refractory mortar, according to the directions from the manufacturer. If specified, moisten the surfaces of the brick that will come into contact with the mortar.

Apply refractory mortar to the edges of the new bricks with a trowel. Although mortar joints in the firebox must be small, excess mortar can be placed on the brick for this step and simply removed later.

Slide the mortared bricks gently into their positions until they are flush with the surrounding bricks.

Wipe excess mortar from the area around the joint using the trowel.

Tool the joints with a jointing tool that will allow the new joints to match the surrounding old joints.

Clean off any mortar from the face of the brick, hearth or any other structures, using a damp sponge. Take care not to damage the new mortar joints that have just been created.