How to measure the bench
Section 903.5 measures to the top of the seat surface: 17 in. minimum and 19 in. maximum above the finish floor. On a slatted or cushioned bench, measure to the top of the slats or the cushion where a person sits, not to the frame.
Section 903.3 sets the seat itself at 42 in. long minimum and between 20 in. and 24 in. deep. The depth is a range, not just a minimum: a bench deeper than 24 in. fails as surely as a shallow one. Length runs along the wall, and a longer bench passes as long as the depth and height hold.
Back support or a wall
Section 903.4 gives two options. The bench is affixed to a wall, so the wall serves as the backrest, or the bench carries its own back support. A freestanding island bench in the middle of a locker room needs the second option.
Where a back is provided it must be 42 in. long minimum and run from a point 2 in. maximum above the seat surface up to a point 18 in. minimum above it, with the support no more than 2½ in. behind the rear edge of the seat, measured horizontally. A gap larger than that between seat and backrest breaks the rule.
Clear floor space and where the bench goes
Section 903.2 requires a clear floor space at the end of the bench seat, positioned parallel to the short axis of the bench. Section 305.3 sizes it at 30 in. by 48 in. minimum. That space is for a transfer from a wheelchair onto the end of the bench, so it cannot be taken by a locker door swing, a trash receptacle, or a scale.
Section 803.4 puts a bench complying with 903 inside every dressing, fitting, or locker room that has to be accessible, and 222.1 sets how many rooms that is: 5 percent, and no fewer than one, of each type of use in each cluster. Section 903.6 requires the bench and its anchorage to take a 250 pound force at any point, and 903.7 requires a slip resistant seat that does not hold water where the bench sits in a wet location.
Lockers beside the bench
Section 225.2.1 requires 5 percent of lockers, and no fewer than one of each type, to comply with 811, which sends their operable parts to the reach ranges of Section 308 and the operation rules of Section 309. For an unobstructed forward reach, 308.2.1 puts the handle, latch, hook, and shelf 48 in. maximum and 15 in. minimum above the floor.
Section 309.4 requires the latch to work with one hand, without tight grasping, pinching, or twisting of the wrist, at 5 pounds of force or less. A padlock hasp that needs two hands, or a dial that must be turned with a pinched grip, is the usual failure. Specify the accessible lockers with a lever latch and place them where the bench's clear floor space stays open.