Efflorescence is a common problem with masonry. In this post, we'll talk about how it occurs, and ways you can reduce efflorescence in construction.
“Efflorescence is a deposit of salts, usually white, formed on a surface, the substance having emerged in solution from within either concrete or masonry and subsequently been precipitated by reaction, such as carbonation, or evaporation.” – American Concrete Institute
The Three Conditions That Must Exist for Efflorescence to Occur
- The presence of salts, most commonly calcium carbonate, sodium sulfate, and potassium sulfate. The salt can come from within the masonry unit itself, the mortar, or even the ground surface.
- Water contact that dissolves the salts so they can travel to the surface. The primary source of moisture that contributes to efflorescence is rain water.
- The pore structure of the masonry is such that it lets the salt solution travel to the surface where it can dry.
Reducing Efflorescence on the Job Site
While many steps are taken by masonry and mortar manufacturers to produce materials that reduce the contributing factors to efflorescence, there are some design and job-site actions that can be taken as well. These include:
- Waterproof all walls below grade.
- Use a drainage wall system that provides an air space between the exterior masonry and other wall elements. When it’s not possible to provide an air space, use a damp-proof coating between the exterior surface and the exterior masonry.
- Prevent moisture from entering masonry by directing it away from horizontal surfaces such as sills and tops of walls.
- Reduce the potential for condensation (especially in buildings that include pools, kitchens, frequent use of steam, etc.) with a ventilation system and use appropriate vapor barriers.
- Store masonry units, cementitious materials, sand and water off the ground to avoid moisture that exists there, as well as contamination by plant life and other organic materials.
- Use a waterproof cover on the materials stored at the job site and make sure to cover unfinished walls to prevent water from entering prior to completion.
- Only use clean, potable water free of salts, deleterious acids, alkalis or organic materials. The water used on site can be a source of salts.
To learn more about efflorescence and other challenges, download Controlling Moisture in Masonry today.
