Managing the risks of efflorescence

by Michael Micalizzi, CTC

All photos courtesy Custom Building Products
All photos courtesy Custom Building Products

The costs of cleaning efflorescence from grout joints and tile surfaces can range from a lost day on a callback to a financial fortune, depending on the size and type of project on which it occurs. For example, to acid-wash tile on one large project, remediation costs exceeded $100,000 for the labor and the scaffolding. Additionally, the owners were highly concerned by the acid-wash residue potential over the window trims and plantings, expressing fears regarding risk to occupants entering and leaving the building. Often, these issues lead to hiring consultants and attorneys.

Standing water results in efflorescence.
Standing water results in efflorescence.

Efflorescence occurs when mineral salt deposits that have leached or migrated from cement and masonry materials are carried to the surface in moisture vapor. These minerals occur naturally in Portland cement and, when dried, appear as a white film, powder, or crystal. Many kinds of mineral salts have been detected in samples of efflorescence, including sodium sulfate, potassium sulfate, sodium carbonate, calcium sulfate, sodium bicarbonate, and calcium carbonate.

The tile industry has experienced efflorescence for a very long time. Unfortunately, building owners and general contractors (GCs) often believe it is solely the tile contractor or installation material supplier’s responsibility to both prevent it from happening and remove it when it occurs. Although poor installation methods can cause it and certain products are more susceptible to it, in many cases, building design and product selection causes or contributes to the problem in both interior and exterior applications.

New concrete and mortar beds will provide a source for efflorescence in a wide variety of projects. For example, when porcelain tiles are installed in exterior applications, the mortars used are polymer-modified, so when the standard-setting, Portland cement-based mortars are used instead of rapid-curing, calcium aluminate-based types, they retain moisture for an extended time, adding to the possibility of salt migration.

Efflorescence from minerals in natural stone.
Efflorescence from minerals in natural stone.

 

To prevent this issue, it is important to address the main causes resulting in or contributing to efflorescence, namely:

  • tile installation practices;
  • choice of installation materials; and
  • building design options and installation flaws.

Design/construction professionals will likely be familiar with many of these issues, but unfamiliar problems may catch a team by surprise.

Tile installation practices

A contractor’s proper, moderate, and controlled use of water during an installation is critical to lessen the risk of efflorescence. Over-watering grout, using too much water to finish grout, and leaving excess water on the tile or grout surface can result in a light residue or substantial blooms of efflorescence.

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