How to Reface a Flagstone Fireplace

Slip on a pair of rubber gloves, dust mask and safety goggles. Combine a tablespoon of tri-sodium phosphate, knowns as TSP, and a gallon warm water in a plastic bucket. Stir the mixture until the TSP is dissolved.

Dampen a plastic scrub brush with the mixture. Work it into the flagstone fireplace to remove any soot, dirt, debris or mold. Once the stains are completely eliminated, dampen a kitchen sponge with water. Rinse away the TSP residue. Allow the fireplace to dry completely before continuing.

Combine the sandstone-patching compound according to the package directions. Load the product onto a putty knife. Apply it to any cracked or chipped sandstone by swiping it across the damaged area. Apply slight pressure to the putty knife to work the compound into the damage. Wipe away the excess product immediately with a damp cloth.

Allow the product to dry at least three to four hours before sanding down the dried patching compound with 220-grit sandpaper until it’s flush with the surrounding surface. Wipe away the sanding dust with a damp cloth.

Protect the walls, flooring or any other areas surrounding the flagstone fireplace with plastic tarp before applying a thin layer of masonry primer to its surface with a brush or roller. Allow the primer to cure for at least eight hours before applying the paint.

Apply a thin layer of latex or masonry paint to the fireplace with a paintbrush or roller. Use back-and-forth movements to prevent creating noticeable lines. Allow the first coat to set for at least three to four hours before applying a second or third coat.

Allow the final coat of paint to dry for at least 24 hours before removing the plastic tarp and using the fireplace.