Local chimney masonry repair in Oakleaf Plantation

Repair mortar no harder than the wall

When new mortar goes into an old wall, it has to work with the brick and mortar already there. BIA's guidance for repointing sets the rule: the compressive strength of the repair mortar should be equal to or less than that of the existing mortar.

A harder repair mix does not share movement with the soft mortar around it. Instead it pushes stress onto the edges of the brick, and BIA names the outcome as spalling. That is why a bag of the strongest mix is not the default choice, and why we look at the existing joints before choosing what goes into them.

Salvaged brick from the same chimney

The closest match to the brick in a chimney can be more of the same brick. When the top of a stack is relaid, sound units from the dismantled courses are cleaned of old mortar and reused. When only a few units are needed, brick can sometimes be taken from a part of the chimney that is hidden, such as inside the attic, and replaced there with a new unit where color does not matter. Salvaged brick has already weathered with the rest of the stack, so it blends in sooner than new brick does. Salvaged units are checked for cracks and soft faces before they are reused.

Brick under paint or a coating

Paint and some coatings on brick form a film that slows the escape of moisture. Water that gets into the brick through a crack or open joint then dries out more slowly behind the film, and the face can peel, blister or crumble under it.

When we repair a painted chimney, the damaged area is opened up, the brick and joints are repaired, and the question of the coating is raised with you. Repainting over the repair seals the same problem back in, so options such as removing the coating are laid out for you to decide on. If the coating stays, the repair is primed and painted only once the new mortar has cured.