When you think of countertops for kitchens or baths, you might think of the materials, or of the tasks that will be performed on them. You think of matching the material to the task at hand – say, granite or concrete for kitchens, and, perhaps, tile or solid
surfacing for the bath.
This typifies the thought process surrounding countertops. And many times, we, as kitchen and bath designers, can impart some unique detail found in an edge treatment or tile arrangement. But how many of us really view countertops, walls and backsplashes as sculpture, as a way to create something truly unique?
Take, for instance, a monolithic pour of a concrete wall and countertop. There's an undeniable impact when the wall and the counter it supports are fused into an integral, sculptural form.
In the case of a concrete wall, it is simply a countertop turned on edge in many ways. Thus, many of the techniques you'd use to create a concrete countertop also apply to the wall. Like a countertop, a wall is poured into a mold, and whatever shapes, textures or design elements you put into your mold will be preserved. Thus, that wall provides many opportunities for simple, cost-effective design interventions that result in truly beautiful and sculptural effects.
However, a wall for the kitchen or bath differs from a countertop in several key ways. First, weight can be a challenge. A 2.5"-thick floor or countertop spread across many square feet doesn't excessively tax the subfloor, but a wall's weight is concentrated over a much smaller space. So you must ensure the walls has proper support.
If you're pouring a wall on a slab on grade, you don't need to worry about reinforcing the floor. But if you're planning to pour a wall over a wooden subfloor, you must consider the wall's weight in relationship to the floor's strength weight in relationship to the floor's strength. (Remembering that a cubic foot of concrete weighs about 140 pounds, and a yard about 3,780 pounds.)
You'll also need to consider the orientation of the wall to the floor joists, noting that the weight of a wall that runs perpendicular to the joists will be distributed more effectively than that of a wall running parallel to the joists.
You may want to consider pouring a concrete footing below the subfloor or pouring a series of footings that penetrate the subfloor and tie directly into the wall. You could also use lightweight aggregates, hollow walls, or both.
However, be careful with your calculations. Lightweight aggregates can reduce the weight of concrete by as much as 30 pounds per cubic foot, but even this may not be light enough for your floor. And while building a hollow wall lessens the weight of the wall even more, it also weakens it. Furthermore, if your wall functions as a bearing wall, you may want to enlist the help of a structural or civil engineer.
Finally, the form for a wall must withstand massive forces. The height of a wall determines the pressure on the form, and the it rises exponentially with every additional inch of height. Thus, be sure to properly brace the wall.
To brace a form, you can use form ties and external bracing, or just external bracing. Form ties work by tying the form's two sides together, acting as a tension member between the walls of the form. They work well, but do leave a hole or, depending on the type of ties used, a series of metal or plastic tabs.
Although a wall can be braced externally without form ties, form ties shouldn't be used without external bracing. Only external bracing can keep the form walls from toppling over during the pour. An advantage to just using external bracing is that it leaves no holes or tabs. But the risk of failure is greater, and the form can also be costly and time-consuming to build and difficult to install without form ties.
You should also note that the materials you use for the kitchen or bath wall form will directly impact the finished appearance. I find that melamine is a useful material for form-making since it's relatively inexpensive and releases easily from concrete.
Experiment with materials to find the texture you like. Try forms made of wood or other materials, or try a prefabricated form liner. Most commercial form liners are made to create patterns that disguise concrete, making it look like brick, tile or wood. You can also experiment with inserts and inlays (fixing them firmly to the vertical surface) or even "found" form liners like bubble wrap or corrugated fiberglass siding.
Mix, Pour, Finish
We use the same basic mix design for walls as we use for countertops. Because walls require such high volumes of concrete, using integral color in a wall pour can be quite expensive, depending on the installation. So, if you want color, you can try acid stains.
With an integral countertop-and-wall pour, there is a large exposed surface area to hand-finish during pouring. It's handled like a poured-in-place slab. The trickiest part of pouring a wall is that the wall forms might fail under the stress of the wet concrete, so always keep an eye out for signs of danger.
Lastly, the longer you leave concrete undisturbed in a melamine mold, the harder and smoother the finish will be. For the hardest finish we'll leave the forms on for at least 10 days.
In the end, remember that combining concrete walls with kitchen and bath countertops is just one way to interpret design and function with new forms and looks. Be creative and have fun making a truly unique kitchen or bath design, no matter what surfacing materials you use.