Chimney masonry repair in Switzerland by local masons

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.

Tooling new joints to match the old ones

The shape of a mortar joint's face is part of how a wall looks. Some chimneys have concave joints, some flush, some struck or raked back from the brick face. New joints tooled to a different profile stand out even when the color matches.

So after new mortar is packed in and has stiffened enough, it is tooled with a jointer that matches the existing profile. Timing matters: tooling too soon smears the mortar, and tooling too late leaves a rough surface. The finished joint should read as part of the original wall. Where the old joints vary around the stack, we match the ones beside each repair.

Protecting fresh joints while they cure

New mortar needs time to cure, and heavy rain on a fresh joint can wash out its surface and weaken its bond. BIA's cleaning and construction guidance recommends covering the tops of walls and openings with a waterproof membrane at the end of each work day and during stoppages.

On a chimney that means covering the top and any open work before we leave, and checking the forecast when scheduling. Fast drying in strong sun or wind can also weaken new joints, so exposed repairs may be shaded or lightly misted. Those steps affect how the work is scheduled, so they are planned from the start.