One of the most common foundation ailments is a white powdery substance that appears on the ground under your home, on the floor framing, or on your foundation or basement walls. Although most people mistake the white powder for a fungus (fungus is typically green or black), it's really efflorescence, which is a growth of salt crystals caused by evaporation of salt-laden water.
Efflorescence appears when mineral salts in the concrete or mortar leak to the surface. While efflorescence is not particularly destructive, it is unsightly and can, in some cases, result in splintering or minor deterioration of the surface it grows on.
The area below the main floor and within the foundation walls can consist of a concrete slab, a crawlspace, or a basement. With each of these configurations come a host of specific maintenance routines that can safeguard your home's integrity.