My two-flat buildings in Chicago have bad efflorescence and spalling of the clay brick masonry in the basements. The basements are heated, so it is unlikely that the brick are freezing. Concrete walkways adjacent to some of the buildings are sloped toward the basement walls. What can I do to prevent the efflorescence?
Efflorescence occurs when soluble compounds in the masonry are deposited on a face of the wall. Spalling can occur from pressures generated by the crystallization of salts within the masonry. The best way to eliminate an efflorescence problem is to eliminate the source of moisture. There are several potential sources of moisture in this wall system. Some water may be penetrating through the outside face of the foundation wall. If there is no effective coating or membrane on the exterior surface of the wall, water from the soil can penetrate and saturate the masonry. If the concrete walk slopes toward the wall, masonry at the base of the wall can become saturated. Water also may be entering the masonry through windows or other features above the foundation. To address water penetration through the outside of the foundation, the best repair would be to remove the soil against the foundation, install or replace the waterproofing, repair the drain tile as needed, and backfill the wall with a well-draining fill. The membrane on the face of the foundation should extend 6 inches above the finished surface of the concrete. A new concrete sidewalk should slope away from the building to prevent water from ponding against the wall. A flashing should be installed through the outer wythe of brick above the top edge of the waterproofing. This repair is expensive and unless considerable water leaks into the basement, it may not be warranted. A more common approach is to repoint the masonry above the foundation. Use mudjacking to reslope the concrete slab so it sheds water away from the building. Then seal the joint between the concrete and the masonry with sealant or cover the joint by setting flashing in a reglet in the wall, extending it down, and sealing it to the concrete slab. The repointing will reduce the amount of water penetrating the wall, and flashing at the concrete should reduce the amount of water that saturates the soil along the foundation. Remove and replace any damaged bricks on the interior. With this approach, some efflorescence and spalling will likely continue over time. Additional units can be replaced as necessary.