The white marks and patches that appear on the brickwork of new and recently built properties are one of the most common questions about new build homes. The phenomenon is called efflorescence and is caused by a well-understood natural process involving water and soluble salts within the masonry.

What Is Efflorescence

Efflorescence is the term for the white, powdery or crystalline deposits that form on masonry surfaces including brick, stone, mortar, and concrete. The word comes from the French for blooming, reflecting the way the deposits appear to bloom on the surface. The deposits are typically calcium carbonate, sulphates, or other soluble mineral salts that are naturally present within brick, sand, cement, or the aggregates used in construction.

How It Happens

When water enters masonry, whether from rain, construction moisture, or the inherent moisture in newly laid materials, it dissolves the soluble salts present within the materials. As the water migrates toward the surface and evaporates, it carries the dissolved salts with it. When the water evaporates at the surface, the salts are left behind as a white deposit. New buildings are particularly prone to efflorescence because they contain large quantities of moisture introduced during construction: cement mortar, concrete, and brick all contain significant water, and this construction moisture gradually migrates outward through the new masonry.

Is It Harmful

In most cases, efflorescence on brickwork is a cosmetic issue rather than a structural one. It indicates that moisture is moving through the masonry, which is normal in new construction, and in most cases the staining reduces and disappears as the building dries out over the first one to two years. However, persistent or recurring efflorescence after the building has dried out may indicate an ongoing source of moisture ingress that should be investigated, such as a failed damp proof course, water penetration at a junction, or inadequate drainage away from the building.

Removing Efflorescence

For cosmetic removal, efflorescence can be brushed away using a stiff dry brush once it has dried out and crystallised. Brushing when wet may work the deposits further into the surface rather than removing them. For more stubborn deposits, proprietary masonry cleaners containing dilute acids such as hydrochloric or phosphoric acid can dissolve the salt deposits, but must be used carefully to avoid damage to the brick face and surrounding surfaces, and rinsed thoroughly after application.

Summary

White staining on new build bricks is efflorescence, caused by soluble salts being carried to the surface by migrating moisture and deposited when the water evaporates. It is particularly common on new buildings because of the construction moisture in cement and brick. In most cases it reduces naturally as the building dries out over one to two years. Dry brushing removes the deposits. Avoid sealing the surface as this traps moisture.