Efflorescence typically manifests as what kind of surface residue on concrete?

Efflorescence is a phenomenon that occurs when water moves through porous building materials, such as concrete, bringing soluble salts to the surface. As the water evaporates, these salts are left behind, resulting in a distinctive residue on the surface. This residue typically appears as a white, chalky powder, which is composed mainly of calcium carbonate and other mineral salts.

This characteristic appearance can help inspectors identify possible moisture issues behind the concrete, such as leaks or high humidity levels, which are contributing to the efflorescence. In contrast, other forms of residue like black spots may indicate mold or mildew, colorful patches might suggest different types of contaminants or water intrusion, and dust residue generally does not correlate with the chemical processes involved in efflorescence. Understanding this will assist home inspectors in diagnosing potential issues related to moisture and structural integrity.