Protruding Objects and Headroom (2010 ADA Standards 307)

The limit applies only to leading edges MORE than 27 in and NOT MORE than 80 in above the floor, the band a cane sweeps under and a person walks into. Below 27 in a cane finds it and above 80 in you walk under it, and 307.2 limits neither -- so the fix for an over-projecting object is often to LOWER it, which is the opposite of what people try. It gives all three moves. A post-mounted object gets 12 in, three times a wall-mounted one. Overhead, 80 in of clearance, and anything less needs a barrier whose LEADING EDGE is 27 in max: a rail at waist height is not a barrier, because the cane has to find it.

the projection limit applies where the leading edge is more than 27 in and not more than 80 in above the finish floor: 4 in for a wall-mounted object, 4.5 in for a handrail, 12 in of overhang for a free-standing object on posts or pylons. Outside that band 307.2 sets no limit. Clear width remaining = path width - projection, which must still meet the required route width. Vertical clearance 80 in minimum, or a barrier whose leading edge is 27 in maximum.

2010 ADA Standards for Accessible Design, 307.2, 307.3, 307.4, and 307.5. A US federal standard in the public domain, quoted directly.

The 2010 ADA Standards are published in full at no cost at ada.gov and by the US Access Board.

Estimate. AHJ and licensed professional govern.

Field names used by the API: mounting, leading_edge_height_in, projection_in, corridor_width_in, required_route_width_in, vertical_clearance_in, max_projection_in, projection_excess_in, drop_to_cane_zone_in, raise_above_zone_in, remaining_width_in

• Limited band leading edge more than 27 in and not more than 80 in above the finish floor2010 ADA Standards 307.2
• Wall-mounted limit 4 in maximum horizontally into the circulation path2010 ADA Standards 307.2
• Handrail 4 1/2 in maximum2010 ADA Standards 307.2 Exception
• Post-mounted 12 in maximum overhang when located 27 in minimum and 80 in maximum above the floor2010 ADA Standards 307.3
• Vertical clearance 80 in minimum, or a barrier with its leading edge 27 in maximum above the floor2010 ADA Standards 307.4
• Clear width protruding objects shall not reduce the clear width required for accessible routes2010 ADA Standards 307.5