We live in a world of conformity and standardization. Almost all base kitchen cabinets are 25 inches deep. Somehow it was determined that a 26 inch countertop depth (25 inches for cabinets and a 1 inch overhang was a reachable depth both in the cabinets and on the countertop.
We would agree that a cabinet depth of more than 25 inches means that items will disappear in the back of the cabinets never to be found again. But where is it written that the cabinets must be mounted so that the cabinet backs are up against a wall? The cabinets can be placed away from the back wall which will allow you to build a deeper countertop. As well, the vacant space behind the cabinets makes it easy to run plumbing and electrical services along that wall as it is no longer necessary to run wires or water and drain pipes through the cabinetry.
Consider moving the cabinets away from the back wall by 4 inches. This will give you a countertop depth of 30 inches (4 inches from wall plus 25 inches of cabinet depth plus a 1 inch overhang) which is a more convenient work surface depth for most individuals.
Countertop edges
Because you are working with a material that conforms to any shape you have a wide choice when it comes to the front edges of the countertop. You can create any of the standard countertop edges using creative placement of moldings in the mold before you pour the concrete.
At a minimum the edges of your concrete countertop should be rounded both for safety and aesthetics. A basic rounded radius of 1/4 to 1/2 inch will work if you do not want to entertain creating more complex edges.
Note: Edges that are rounded less than a 1/4 inch are likely to chip over time.
It is also relatively easy to insert a slot in the front edge in order to accept a metal, such as brass, or a hardwood trim.
Always remember that when working with molds, you are working in reverse. If you want a slot, you add material to create a slot. If you want a fancy edge you must create a molding that has the reverse profile of the edge that you want in the concrete.
Countertop overhang
Although concrete gives you the flexibility of having any amount of overhang you want, in the front of the countertop, where there are drawers and/or cabinets below the overhang, you want to limit the overhang to between 1 and 1 1/2 inches. A deeper overhang will cause you to wrap your knuckles when you open drawers or cabinet doors.
You also want to keep the front edge of the sink knockout no more than 3 1/2 and preferably 4 inches from the front edge of the countertop. If it is deeper than 4 inches you will find it uncomfortable to work.
Kitchen sinks and bathroom basins
Kitchen sinks
Kitchen sinks come in two basic formats, surface mount and undermount. For concrete countertops an undermount sink is usually chosen, however if you prefer the aesthetics of a surface mount there is absolutely no reason why you cannot use one.
Whether you choose surface mount or undermount we recommend that you use a stainless steel sink as it works aesthetically well with concrete. It is also lightweight. If you are considering an undermount porcelain sink, we recommend against it. Porcelain sinks are very heavy and have a rounded edge structure which can make mounting the sink to the underside of the concrete countertop difficult.
As this website is structured for the do it yourself individual, who in most cases is looking to save a few dollars by completing the project as inexpensively as possible we will not discuss custom built stainless steel sinks, which many books will recommend.
The sink must fit in the base kitchen cabinet that is designed to house a sink with a standard material countertop.
Note: You will have to choose your sink and preferably purchase it before building your countertop. It is critical to know the exact dimensions of the hole for the sink before constructing the mold. As well, having the sink will allow you to position the hole for the kitchen faucet and any other accessories such as soap dispensers or hot water spouts that you may wish to install in the concrete countertop.
Note: When calculating the measurements for the sink, do not forget to include the space needed for the sink mounting hardware.
Continued - Bathroom basins for concrete countertops
How to Make Concrete Countertops - Index