MANUFACTURED STONE HAS BEEN around for several decades now, but in recent years, the cement-based material has come of age, both in terms of technology and in its warm reception by residential designers and builders.
Dave Hall, owner of the masonry company that bears his name in Ripon, Calif., says the stone rush has arrived. He operates six crews of five men full time, putting about 250,000 square feet of veneer stone up each year. Some of that work is commercial, covering the giant acoustic walls that surround new subdivisions, but his residential contracts are growing fast. It's full-time work.
“I'm doing a whole subdivision of 80 houses right now,” he says, “with between 400 and 1,000 feet of rock [manufactured stone] on each one.”
Hall works primarily with Cultured Stone but has also used Eldorado and other brands. He says the installation processes for various brands of manufactured stone are similar. The biggest differences have to do with stone design and color variations. And no one color or shape wins the regional popularity contest.
“Every style is popular,” he says. “I install stone from Sacramento to Sonora, and everybody wants something different. As soon as they see that a style is popular, they switch to something else.”
Technology Boost Jamie Scholl, a field superintendent for John Ginger Masonry, Riverside, Calif., works primarily with Eldorado manufactured stone products. He notes that premixed mortar has taken a lot of the guesswork out of installation because it eliminates mistakes in achieving the best mix for adhesion. In addition, because manufactured stone is lighter and more consistent in shape and color than natural stone, it requires less intensive labor to install. Those factors help account for the speed with which builders and masons have adopted the product.
“Products like Spec Mix are preblended,” Scholl notes, “so the color is already in them and always the same.”
Hall adds that the science of premixed mortar has become key to selling clients on the look of manufactured stone jobs—and his success. He says that not too long ago, he mixed all mortar on the jobsite, taking sand from one pallet, cement from another, and adding color on the fly.
He now takes mortar mixing to the next level, by analyzing the stone he uses and choosing his mortar based on the stone type. “I look for the darkest color in the stone and find a mortar that matches that color,” he explains.
Color, Shape, And Labor Problems with color variations between different batches of manufactured stone have become rare, thanks to improvements in the manufacturing process. Both Hall and Scholl have seen occasional color inconsistency. Hall blames it on molds at the plant that outlast their effectiveness. He says the companies usually address the problems without much fuss. Scholl says that working with smaller manufacturing companies occasionally leads to bigger color variations, because they tend to produce smaller batches of each color pattern. Every new batch requires a new color mixing.
“The better manufacturers don't have inconsistency of color between batches,” Scholl says, “where some of the backyard manufactured stone guys might have a problem. We really rely on the stone companies to have a good handle on it, because the amount of labor changes depending on the color and quality of the finish of the stone.”
Other factors that affect labor include the shape and size of the specific line of manufactured stone. For instance, says Hall, “the easiest stone to install from Cultured Stone is River Rock. That's because they're all basically round stones, and there's no special pattern you have to follow.”
Scholl adds that installers use different tools for cutting different rocks. This also affects labor. “On rounded types, for example, my guys just whack it with their trowel,” he says. “On drystack, we use a diamond-blade saw.”
Builder'S-Eye View One frequent mistake builders make in applying manufactured stone is letting it run all the way down the wall to soil grade, says Scholl. Like any other siding material, it needs to be properly flashed at the junction between foundation and framing to avoid moisture infiltration or staining.
“One solution we do for one builder is to apply stone separately to the foundation wall,” Scholl says. “That way you also get a nice visual-depth effect.”
“The only reason more builders don't [use manufactured stone] is its price,” which is higher than that of other siding materials such as vinyl, fiber cement, and stucco, says Scholl. He adds, however, that the price difference may be smaller than they anticipate. “What they need to know is that they don't need to do anything different in preparation than they would with a stucco job. The other thing they need to keep in mind is that it's easier to sell a home with a stone finish.”
Below The Belt Working with any manufactured stone, the toughest transition point can be where the framing ends and the foundation begins. Resist any temptation to run the stone all the way to grade. Doing so can cause the manufactured stone to stain or oxidize. To create a clean line at the wall base, build a short jig from 2x4 lumber, as shown, that can be staked into the ground and leveled. The transition can be flashed at the base of the wall the same way you would with stucco. See the manufacturer's installation guide.
Substrates On Parade When applying cementitious stone to home exteriors, the process varies slightly depending on the framing system.
Over Gypsum (Interior Walls) Longtime pros like mason Dave Hall note that interior veneer stone is not required to be placed over metal lath—but he uses lath as a rule, the same way he would on an exterior. Simply overlap the lath by at least 2 inches, the same way you would on an exterior, and screw, nail, or staple into 16-inch framing at approximately 6-inch intervals vertically. See installer's specifications for more specific instructions, and check local codes.