Granite countertops are cut from slabs in thicknesses that allow the stone to easily support a traditional cabinet overhang of two to four inches. A kitchen island cabinet often calls for a larger countertop overhang of 12 to 16 inches or more at one side for a bar or seating. There is a simple method that will provide the support necessary in an attractive way to complement the cabinets and countertop.
Layout corbel locations on the overhang-side of the island cabinet. For example, for an island supporting a 48-inch countertop width, with a four-inch edge overhang and 16 inches on the supported end, four 12-inch corbels spaced roughly 16 inches apart will match the cabinet style and provide support for the countertop overhang.
Plumb the corbel centre lines down the outside and inside walls of the island cabinet using a level. The remaining corbel centres should be equally spaced between the two outside corbels.
Drill the pilot holes for the corbel screws from the inside face of the cabinet wall. Define three equally spaced centre points within the length of the corbels, and drill the pilot holes for the corbel screws. Refer to the corbel manufacturer's specifications for fastener placement and sizing.
Apply a layer of wood glue to the mounting face of the corbel being installed, then align the corbel with the layout line, and the top surface flush with the top of the cabinet.
Secure the corbel to the cabinet wall with wood screws. Use a damp cloth or sponge to wipe away any wood glue that squeezes out of the corbel-cabinet connection.
Repeat Steps 3, 4 and 5 for the remaining corbels.
Allow the wood glue joints to cure for a minimum of 24 hours before installing the granite countertop.
A wide range of manufactured wood corbels is available at most home improvement stores, making many options available to match your cabinet design. For ease of access and installation of the countertop supports, the installation of the corbel supports is best completed prior to installation of the granite countertop.