The reach depth to controls mounted over obstructions cannot exceed the depth of the knee and toe clearance. Reaching beyond the front edge of the toe clearance is not permitted.
Operable parts designed to be used by building occupants, including but not limited to, thermostats, dispensers, light switches, fire alarm pull stations, etc., must be located so that they are accessible to everyone. Technical standards referenced by federal, state, and local laws and building codes include design criteria developed to ensure that operable parts are accessible. A 30 x 48 inch clear floor space is required to be positioned at the operable part to support one of two types of reaches: a forward (perpendicular) or a side (parallel) reach. Of the two reach types, each can be unobstructed or obstructed. Unobstructed forward and side reaches do not require reaching over an element to access an operable part. Conversely, obstructed forward and side reaches require reach over an element, such as a countertop or shelf, to access an operable part. Of all the reaches to operable parts, the obstructed forward reach is the most challenging to design and construct. As we always say, the devil is in the details, so proper detailing of the obstructed forward reach is critical to nail down in design.