Engineering and Construction

Moisture that travels through basement walls can damage wall coverings, such as wood paneling.

Moisture traveling through the basement walls can also cause musty odors or mildew growth in the basement areas. If the wall should freeze, then the expansion of freezing water in any cracks or joints may cause deterioration of the wall.

The moisture that is passing through the basement wall will usually contain dissolved salts. The penetrating water may often contain salts originating from the ground or mineral salts naturally present in the wall materials. As the water evaporates at the interior wall surface, the salts form white crystalline deposits (efflorescence) on the basement walls. Figure 11.23 shows photographs of the build-up of salt deposits on the interior surface of basement walls.

The salt crystals can accumulate in cracks or wall pores, where they can cause erosion, flaking, or ultimate deterioration of the contaminated surface. This is because the process of crystallization often involves swelling and considerable forces are generated. Another problem is if the penetrating water contains dissolved sulfates, because they can accumulate and thus increase their concentration on the exposed wall surface, resulting in chemical deterioration of the concrete (ACI, 1990).

The effects of dampness, freezing, and salt deposition are major contributors to the weathering and deterioration of basement walls. Some of the other common deficiencies that contribute to moisture migration through basement walls are as follows (Diaz et al., 1994; Day, 1994f):

1. The wall is poorly constructed (for example, joints are not constructed to be watertight), or poor-quality concrete that is highly porous or shrinks excessively is used.
2. There is no waterproofing membrane or there is a lack of waterproofing on the basement-wall
exterior.
3. There is improper installation, such as a lack of bond between the membrane and the wall, or deterioration with time of the waterproofing membrane.
4. There is no drain, the drain is clogged, or there is improper installation of the drain behind the basement wall. Clay, rather than granular backfill, is used.
5. There is settlement of the wall, which causes cracking or opening of joints in the basement wall.
6. There is no protection board over the waterproofing membrane. During compaction of the backfill, the waterproofing membrane is damaged.
7. The waterproofing membrane is compromised. This happens, for example, when a hole is drilled through the basement wall.
8. There is poor surface drainage, or downspouts empty adjacent the basement wall.