By Russ Lee
A key element in the overall design of the island was that the solid surface top should appear to be "floating" in the air. No support brackets of any kind were to be visible. To make the challenge even more difficult, the top stile of the 32mm cabinet had a reveal of 5/8", and the designer insisted that the bottom of the countertop lip sit exactly 1/8" above the top edge of the drawer fronts. That meant we had just 1/2" between the bottom of the solid surface deck and the top of the cabinet to create enough support to suspend an 18" overhang.
It was an engineering nightmare. We wanted to please our client by preserving the designer's vision of weightlessness, while building a top that would be safe. In the end, we had to acknowledge the laws of physics, and convinced the designer to reduce the size of the overhang.
For our part, we created a substrate support made of 1/2" plate steel, which covered the entire island cabinet and overhang area. Where the steel covered the cabinet box, we made cut outs in the steel to comply with the solid surface manufacturer’s warranty requirements. The entire sub-structure was glued and screwed to the cabinet box, after which the solid surface top was installed.
Solid surface is unique as a surfacing option because most manufacturers offer a 10-year, transferrable, installed warranty, which often covers labor and materials. Understandably, for such a comprehensive warranty to remain in effect, both the fabricator and homeowner must comply with a rigidly defined set of standards. For their part, homeowners must remember to avoid putting hot pots and heat-producing appliances directly on the countertop surface. The fabricator must employ industry accepted fabrication techniques, while following strict guidelines set forth by the solid surface manufacturer for fabrication and installation. One of those guidelines governs the size and support structure of overhangs.
The Corian Fabrication Manual states that no substrate support is required for overhangs of 6" or less. An overhang that measures 6" to 12" must be supported by plywood underlayment
or brackets, and one extending 12" up to 18" must incorporate plywood underlayment and brackets. Anything over 18" requires legs or columns extending to the floor.
That means if you want to incorporate a 12" overhang on a peninsula top, for example, so that your clients can comfortably sit at the counter and eat without banging their legs into support brackets, it can be done with properly installed plywood underlayment. If the overall height of the countertop is an issue, however, or the design of the cabinets will not allow for build-up under the solid surface top, support brackets would be required with that same 12" overhang.
Experienced fabricators have identified alternatives to the plywood and bracket scenario described above. Plate steel or 1" square steel tubing spaced at regular intervals beneath the countertop deck have proven to be acceptable materials for supporting solid surface overhangs. In those cases where brackets must be used, the overall look of the design may be preserved by fabricating corbels from matching solid surface. As a design element, legs and columns constructed of solid surface and creatively decorated with flutes, multi-layered moldings or other effects often add interest to the overall installation.
The bottom line is that the overhang must be properly supported.
According to the Corian Fabrication Manual, the strength of the overhang may be tested by suspending a 100 lb. weight approximately one inch from the edge of the countertop. If the deflection of the solid surface is greater than 1/4", the support is inadequate.
In the case of suspended seating, even though the standard overhang is usually well in excess of 12", it would be ridiculous to consider installing support brackets under the solid surface.
Since the issue of proper support for suspended seating has already been considered in the seating design, your fabricator can take advantage of this engineering to help support the countertop deck. By running the plywood underlayment across the exposed bars of the suspended seating, he can provide proper support for the countertop without the use of brackets. Then, to be certain that the installation will not void the manufacturer’s warranty on the countertop, he can employ the deflection test described above.
By gaining a better understanding of the physical characteristics of solid surface, and by incorporating those parameters into the final design, a kitchen and bath designer can allow his or her imagination to soar when using the product. No other surfacing alternative offers such a wide array of colors, design options like integral sinks and coved backsplashes, or performance characteristics, such as invisible seams or ease of maintenance. And, other than engineered stone, which cannot be seamed invisibly, no other surfacing material offers a 10-year, installed warranty.
Russ Lee is editor of SolidSurface magazine, a bi-monthly sister magazine of K&BDN that is aimed primarily at solid surface fabricators.