Taken at face value, a study of Mexican bricks conducted at Clemson University's National Brick Research Center, in Anderson, S.C., and released in 2004 gives poor scores to several Mexican brick brands. Of the 28 bricks tested under ASTM C-216 by repeated freezing and thawing, only three passed the test.
So should builders be worried about buying Mexican brick? Experts say no. In fact, merely counting the failed bricks in the Clemson study overlooks a critical point: The lab subjected bricks meant for use in South Texas and Florida to tests designed for bricks meant for use in colder climates. The real key to brick choice is grade.
According to Gregg Borchelt, head of engineering and research at the Brick Industry Association, in Reston, Va., all nonpaving bricks sold in the United States for code-governed uses, regardless of origin, must be graded according to a set of tests like those performed at Clemson. The results put bricks in one of two grades: moderate weathering (MW) or severe weathering (SW). The difference between the two is a brick's ability to resist freeze–thaw cycling when wet. (SW bricks are fired to a higher temperature, which strengthens the ceramic bond between the clay particles. This bond is what gives the bricks the strength to resist expansive forces.)
SW bricks are required in 95 percent of the United States. Only a few areas—Southern Florida, Texas, and Arizona—permit the use of MW brick. For every brick shipment, distributors should have a testing lab certificate certifying the bricks' grade.
U.S. producers make mostly SW bricks, but Mexican companies make both. Pete Nava, general manager of Bricks & Tiles Unlimited in San Antonio, has been selling bricks all over Texas for 35 years—both Mexican- and U.S.-made. “The quality control of the Mexican producers is no different from that of the U.S. brands,” he says. “Everything [from Mexico] we've ever tested has conformed [to] our market,” he says. “It sounds as if somebody pulled samples of product planned for use in Texas and tested them in Nebraska.”
That seems to be what happened at Clemson. Glen Duncan, executive director of the Southwest Brick Institute, in Austin, Texas, was one of the people who supplied the Mexican bricks to be tested. “We just walked around and picked them up off job-sites in the Texas region,” he says. “It was never meant to be a scientific process.”
But while the study results don't tell a lot about Mexican bricks, they hold an important lesson for builders: Pay attention to the grade of bricks going into your homes.
Says Borchelt: “The critical message to get out to the builder is to triple-check that brick you put on a building meets the standards for where you're going to use it.”