I own a nearly 100-year-old house in the Chicago area with a brick foundation that is three wythes thick. The inside of the basement walls are covered with white efflorescence. Is this a problem and how can I correct it? Should I dig up the soil on the outside and install a membrane?
The efflorescence most likely is caused by water entering from the soil into the foundation walls. This can be corrected by digging up the soil and installing a new membrane. However, water also can enter along the tops of the walls if flashings are not properly installed. If this is the case, new flashing may need to be installed. These measures may be excessive, depending on the wall's condition and the amount of water that is coming in. Over time, extensive efflorescence can damage mortar and units by crystallizing within these materials, resulting in delamination and crumbling. In some areas, sulfates in groundwater also can contribute to these problems. If such serious damage is confined to isolated areas, rebuilding these portions of the interior wythe may be sufficient. If, on the other hand, substantial areas of the wall have deteriorated to the point where they need to be rebuilt, you should consider removing the soil on the exterior, rebuilding sections as appropriate, and applying a new membrane. You also should examine the exterior masonry above grade to see if it needs to be repointed or if new flashing should be added.