Don't let efflorescence sap your effervescence
/After years of planning, design, and construction, your vision in fired clay brick is finally complete. The finished structure now stands proudly for the world to see. It turned out exactly as you hoped it would — better, even. You are overjoyed, giddy — positively effervescent with enthusiasm for your creation.
Then a few months later, a white, powdery substance starts creeping across your carefully designed facade. It looks like your building is chalked up for the Olympic power lifting competition. It is not attractive, and the rest of the world can see it. You are deflated.
What’s going on here? Efflorescence, unfortunately, has reared its ugly head. Efflorescence is what’s left when water carrying soluble salts and other compounds finds its way to the surface of a masonry facade. The water evaporates, leaving the white residue behind. Despite its tendency to temporarily mar brick surfaces, efflorescence actually has very little to do with the brick itself, since brick doesn’t typically contain or release the compounds in efflorescence. The problem lies in how the materials and environmental conditions around the brick were managed.
Here are some keys to preventing efflorescence on your next project:
Materials selection. Most of the salts that make up efflorescence actually come from cement-based mortars and concrete masonry units that are used in conjunction with brick. Since cements high in alkaline content are more prone to produce efflorescence, lower alkaline products should be used whenever possible. Avoiding trim materials for caps, coping, and sills that contain high levels of soluble salts is a good idea. And, specifying the use of potable water and clean, washed sand in the mortar mix can help.
Design and detailing. For more than 50 years, the Brick Industry Association (BIA) has recommended drainage walls that incorporate an air space, primarily for channeling out any water that penetrates the facade. But, the air space has an important side benefit when it comes to preventing efflorescence. It separates the exterior brickwork from other elements in a wall assembly — particularly load-bearing CMU inner walls that contain large amounts of efflorescence-causing minerals. An adequately-wide, clean air space devoid of mortar spill-overs moves moisture quickly out of the wall system and minimizes the dissolving and transferring of salts. Proper flashing around and between trim materials in the facade serves the same purpose.
Construction practices. Improper storage of masonry materials on the construction site can be a culprit when it comes to efflorescence, as can unfinished, exposed masonry work. Transfer of dissolved minerals can happen when stored brick is allowed to sit directly on the ground, and when it goes uncovered during wet weather. Also, partially completed masonry walls exposed to rain and other elements can become saturated with water that can take weeks — if not months — to dry after the completion of the building.
Looking for more detailed guidance? BIA has several very helpful resources for designers and builders regarding the prevention of efflorescence. Click the buttons below to access them.
