Concrete Counter Tops
Precast Counter top Molds. There are many factors involved in making a precast concrete counter top, but creating the right form for the counter top is key. Wood, formica, melamine, foam, steel and rubber can be used for concrete counter top forms that get the job done.

Concrete is an increasingly popular material for counter tops because it is versatile, durable and environmentally sound. Building molds and precasting countertops in a studio allows designer/fabricators to cast and cure slabs under controlled temperature and humidity conditions.

The mold is a critical component in the success of a precast project. “Remember, moldmaking is an ancient art and craft,” says Fu-Tung Cheng, principal at Cheng Design in Berkeley, Calif. “So many things we have around us are made out of molds, and most of the molds are made of the most prosaic stuff. In the end you won’t recognize the material of the original shape. Just use your imagination to invent something that is an understudy for concrete.”

There are many factors involved in a successful precast countertop — the mix, coloring techniques, workmanship, creative design and more. But they all depend on the mold being right. “A good mold forms the backbone for the rest of the forming,” Girard says.

Choosing your material
While melamine is probably the most widely used material for making molds, contractors actually use a surprising variety of materials. Here are some questions to ask when choosing a material.

First, is it strong? Can it withstand the pressure of the concrete without distorting? Strength and rigidity are some of the advantages of melamine. If a less-traditional mold material is going to be used, it must be properly supported. “The most important factor is that whatever you’re casting on has to be flat and rigid,” says Jeff Girard of The Concrete Countertop Institute in Raleigh, N.C. “The weight of the concrete will cause a suspended form to sag.” If your shop is producing countertops regularly, he recommends investing in a dedicated casting table.

Second, what is the desired finished look? Concrete will mirror the surface it is cast against, so if the slab will be used with little finishing, the mold should imprint the desired surface (usually very smooth). If the counter will be ground and polished, other considerations, such as economy and reusability, become more important in choosing a mold material. Buddy Rhodes of the Buddy Rhodes Studio in San Francisco often casts “right-side-up” so the molded surface will be the bottom of the counter, finishing the top by hand troweling for a hand-crafted, burnished look similar to a cast-in-place counter.

Third, is the mold material affordable and ecologically sound?