Where tables or counters are served by fixed seats, the width of the aisle or aisle accessway shall be measured from the back of the seat. Where seating is located at a table or counter and is adjacent to an aisle or aisle accessway, the measurement of required clear width of the aisle or aisle accessway shall be made to a line 19 inches (483 mm) measured perpendicular to and away from and running parallel to the edge of the table or counter. In the case of other side boundaries for aisle or aisle accessways, the clear width shall be measured to walls, tread edges, or other obstructions.
Exception: Doors, when fully opened, and handrails shall not reduce the required width by more than 7 inches (178 mm). Doors in any position shall not reduce the required width by more than one-half. Other nonstructural projections, such as trim and similar decorative features, are permitted to project into the required width 1.5 inches (38 mm) from each side.
Aisle accessways not required to be accessible by IBC Chapter 11.shall provide a minimum of 12 inches (305 mm) of width, plus 0.5 inches (12.7 mm) of width for each additional one foot (305 mm), or fraction thereof, beyond 12 feet (3658 mm) of aisle accessway length.
Exception: Portions of an aisle accessway having a length not exceeding six feet and used by a total of not more than four persons.