When an over-the-range microwave oven mounts to the wall instead of to the bottom of a cabinet, the wall studs provide the majority of the support for the microwave’s weight. The mounting plate included with the oven is designed for attachment to the wall only, and cannot be attached to a cabinet for mounting. If you must mount an over-the-range microwave oven on a cabinet, the mounting plate that comes with the cabinet serves no use.
To mount an over-the-range microwave oven under an island cabinet, you must purchase a cabinet-mounting kit. A cabinet-mounting kit is designed specifically for installation on the bottom of the cabinet and attaches to the top of the microwave. Since cabinet-mounting kits are made to work with many microwaves, they will not fit the exact dimensions of a specific microwave, so they don’t normally have the same amount of strength as wall-mounting kits.
Cabinet Weight Limits
A major factor in whether or not an island cabinet can support an over-the-range microwave is the weight limit of the cabinet. The paperwork that comes with a cabinet generally lists the amount of weight that the cabinet supports. Even if the weight limit of a cabinet exceeds the weight of the microwave, that doesn’t mean that the cabinet will support the microwave. You must also factor in the weight of the items inside the cabinet.
Whether a cabinet can actually support the amount of weight listed in the paperwork depends upon whether the cabinet was properly installed in the first place. When installed to the ceiling, island cabinets must be mounted to the ceiling joists. If the cabinet does not have the proper original installation, it may not support the specified weight. To check the original mounting, use a stud finder to find the joists in the ceiling and make sure that the bolts that attach the cabinets to the ceiling line up along the stud.