These are beautiful natural gray concrete kitchen countertops that we installed in a south Dallas, TX home. As you can see in some of the pictures, the home was in the middle of an extensive remodeling project, and kitchen countertops were just one part of it. This was a cast in place project that took us about three days to build due to their size and layout. This project had two sinks, one an apron style and the other a smaller, oval-shaped prep sink. Most people don't realize just how much work goes into mold building, but it's by far the most critical part of the entire job.
First, no cabinets are perfectly square or level. With precast concrete countertops, this is less of a problem. We square up the edges in our shop, and if the cabinets aren't level, well, that's what shims are for. Cast in place kitchen countertops are trickier. To get these to look good we have to create a mold that rests on the cabinets but is also independent of them so that we can square up and level the countertops. Next we have to consider the faucet that will be installed. Will it need one hole or three? Most faucets are not designed for the extra thickness of concrete; consequently, we have to make a special knockout (void) for them so that they will drop right in. To create a knockout in the countertop for the sinks, we have to cut a foam pattern and carefully align it in the mold.
Apron sinks like the one in this project are a special challenge for concrete kitchen countertops because we have no leeway in their front to back orientation like we do with a traditional sink. Once the mold has been built, we go with the pour and the finishing (trowelling) operations. Finishing concrete needs a special touch. If you do it too soon or too much, the surface can actually peel up. Do it too late or not enough, then it looks like a rough sidewalk. After letting it cure we strip the mold, do any necessary touchups, and seal it to protect it. With concrete countertops, the first thing most people notice are the edges—are they straight, beveled, rounded? We'll go over some of the options in our next project.