Rhodes places his precast slabs on 2x4 sticks to allow for even curing all around. "If the slab is left on the table it will warp, because the top surface will dry faster than the bottom," he says.
Transporting precast countertops to the installation site is a little like handling artwork - which these countertops are, after all. Ship them vertically, stacked on edge. Protect them with shipping blankets or foam, protect the comers and strap them in.
At Stone Soup Concrete, they've invented a lot of equipment to make the job of moving the countertops easier. "We move everything on rolling carts that flip up and down," Gobillot says.
The challenges don't stop once you get to the job site, however.
"Sometimes when we install a counter we bring it from a nice [moist] place into a home that has the heat on and is in the direct path of the southern sun, [and] the counters will warp after a couple of days," Rhodes reports. "If the project is covered and kept moist, the warping will not occur. If they do curl they can be wet with a damp towels, and sometimes they will straighten out."
What to fill the seams with is a matter of preference. Colored, two-part epoxy, color-matched acrylic caulk, and silicon are some of the materials commonly used.
Cheng uses an innovative technique for seams in his precast countertops. "We key all our seams. We make a male-female tongue and groove, so when you push the pieces together they self-level."
Final thoughts
If you are considering trying your hand at either the precast or cast-in-place method of creating concrete countertops, know that there will be a considerable learning curve.
"Don't let anyone foot you that either technique is easy," Ralston cautions. "Both require practice, skill and talent."
Girard agrees wholeheartedly. "Training and practice are essential in making concrete countertops. The pioneers of the industry taught themselves how to make concrete countertops, but there is no need to do that anymore."
Fortunately, more classes are becoming available.
As Girard strongly emphasizes, "I always tell people to get the training they feel they need, then make samples and practice on their own homes before trying to make a concrete countertop for a client - don't use clients as guinea pigs.
Tom Ralston is a third-generation concrete contractor and the owner of Tom Ralston Concrete in Santa Cruz, Calif, which does structural, decorative, and specialty concrete work.
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