One of the biggest advantages of concrete is that it can be poured into almost any mold. It gives us incredible flexibility in creating many outstanding options, such as the ones you can see in this project that we installed in Valley View, TX. For this project, we installed an integral concrete sink and its respective drainboard for the kitchen and bathroom countertops. We only do these with precast concrete countertops. Though it's not impossible to do with a cast in place countertop, it's difficult to control it precisely enough that we don't risk a tear out and redo.
Integral concrete sinks are one of the most challenging options for concrete countertops. If anything goes wrong, we have to start from scratch and a lot of work goes down the tube. As you may have guessed, material cost for concrete countertops is inexpensive, but it's the highly skilled labor needed to build them that's costly. Typically there are two ways of creating an integral concrete sink: one is to use a prefabricated fiberglass mold and the other is to use a custom-built mold. Prefabricated molds have an advantage in that we can reuse them multiple times, while a custom-built mold is a one-off build; you use it once and destroy it when you pull the mold apart. The plus with a one-off is that you can get exactly what you want. The prefabricated molds only have a limited selection available.
We normally use the one-off molds for our concrete sinks simply because we rarely find two customers who want exactly the same sink. For this project, we built two molds—one for the kitchen countertop and the other for the bathroom. When we custom build molds, we normally use foam because they're easier to cut into the final shape and easier to take apart. Both of these concrete countertops were reinforced with steel mesh to minimize the possibility of cracking, and both were poured in our shop and allowed to cure for a couple of weeks. They were lightly polished and then sealed with a polyurethane sealer. We loaded them into our truck, slid them onto the cabinets, leveled them, and gave them the final wax coat.
In our next project, we'll take a look at another kitchen countertop that had a specialty sink in it, though not of the concrete kind.