石積みの白華

Efflorescence forms when water infiltrates masonry and dissolves water-soluble alkaline salts present in the masonry units or mortar. As this water migrates to the surface and evaporates, it leaves behind crystalline salt deposits, typically appearing as white powder patches on brick, stone, or concrete surfaces.

Efflorescence appearing soon after construction can be cleaned using water and a brush. Although it may reappear initially, natural agents like rain gradually wash away salt deposits. Over time, efflorescence reduces as salts leach out of the masonry, and the deposits eventually diminish without requiring additional intervention.

Efflorescence appearing on masonry walls several years after construction completion signals that water has recently begun penetrating the wall. This indicates an active moisture problem requiring investigation. Identifying and repairing the source of the water leak is essential to control further efflorescence occurrences and prevent ongoing damage.

Preventing efflorescence involves using masonry units and clean mortar free of water-soluble salts. Minimizing water intrusion through proper roof drainage and applying waterproof coatings that permit water vapor outward migration are critical. Cavity drainage and flashings in masonry walls provide additional moisture barriers, while cavity wall construction offers enhanced protection against moisture intrusion.

Waterproof barriers applied to masonry walls prevent external moisture entry while allowing water vapor to migrate outward. This dual function stops salt-laden water from entering the masonry while permitting trapped moisture to escape, preventing salt accumulation and efflorescence formation on the surface.

Proper roof drainage directs water away from masonry walls, minimizing water infiltration that dissolves and transports water-soluble salts to the surface. By reducing the amount of water penetrating the masonry, adequate roof drainage significantly decreases the likelihood of salt deposition and efflorescence development on building surfaces.

Cavity wall construction creates an air space between masonry wythes that acts as a moisture barrier, providing superior protection against water infiltration compared to solid wall construction. This additional layer reduces the amount of water reaching the inner masonry surfaces, thereby minimizing salt dissolution and efflorescence occurrence.