Once you have the base cabinets in their final position, reinforced and level it is time to start the first step in actually making the concrete countertop, which is to create a template that will outline the dimensions and position of the countertop, sink, faucet and any other accessories that will be mounted through or in the countertop.
The easiest method to make the template is to use 3 inch strips of thin plywood cut perfectly straight. Cut one of the strips to the correct length of the back wall and place it on the back of the base cabinets.
Note: Remember that the template sits over the base cabinets but is in fact a template of the countertop. So if the base cabinets are out from the wall then the back of the template would still rest against the wall.
Note: You can use some small brads to hold the pieces of plywood in position.
Cut a second piece the length of the front of the base cabinets and place it in position.
Note: The front piece of plywood will overhang the base cabinets. In our example the overhang is 1 1/2 inches.
Note: Throughout this article on making a concrete countertop you will be faced with many decisions. In many cases there is no right or wrong, it is just that you must choose from one or more alternatives, some alternatives will be easier than others. We have reached a point where you are facing one of those areas in the construction. You can build the template so that all of the angles are taken into account. The primary angles being that no two perpendicular walls are at true 90 degree angles. If you are not an experienced mold maker, we highly suggest that you build the template square, as a perfect rectangle. If you build the template to include wall angle discrepancies you will be faced with the problems associated with creating all of those angles in the mold and you must remember that the joints must be water tight, so the angles cannot be close they must be exact. We will continue on with this article as if you are following our recommendation.
The front and back pieces should be perfectly parallel to one another.
Cut two pieces of plywood strips to mark the ends of the countertop and using a hot glue gun, glue them to the back and front pieces of plywood.
Cut another two pieces of plywood strips, to mark the position of the sink and glue them to the front and back pieces of plywood.
Use your carpenter’s square to ensure that all of the pieces are perfectly square with one another.
The finished template should look similar to Figure 10.
Figure 10 - Template of concrete countertop
Make notes on the template for front and back and for the position of holes for faucets and other accessories along with any additional information and measurements that you might require when you make the mold.
When marking the position of the sink take special note that the sink and its mounting fittings clear all the walls of the base cabinet. Also ensure that the faucet does not end up in a position above the back wall of the base cabinet. If you have moved the base cabinets out from the wall, the faucet can go on either side of the back wall of the base cabinet.
Note: There must be a minimum of 1 1/2 inches of concrete surrounding all holes. Any less and the concrete is likely to crack at the narrow points.
Where you might encounter a problem is if your concrete countertop sits between two walls. It is highly unusual for walls to be at true 90 degree angles and trying to create a template that allows for the slight variance in the angles between the back and side walls is almost impossible. One way around the situation is to allow a small amount of space, less than a 1/4 inch between the back and side walls and the template. After the concrete countertop is installed the gap between the walls and the countertop can be filled with a number of materials including caulk, epoxy or you can cover the gap with a backsplash made of tile, concrete or other material.
How to Make Concrete Countertops - Index