The elevator cab shall be a minimum of 54 inches by 68 inches (54" x 68" = 1372mm x 1727mm) measured wall-to-wall and wall-to-door, or may be 60 inches by 60 inches, (60" by 60" = 1524mm by 1524mm) wall-to-wall and wall to wall. The door can be located on any wall or walls.
Exception: In existing buildings, where existing shaft configuration prohibits strict compliance with 521 CMR 28.7, the maximum car size allowable for the existing shaft shall be provided, but in no case shall the inside car area be smaller than 48 inches by 48 inches, wall-to-wall and wall-to-door.
521 CMR, § 28.7