24 CFR 3280.112: Hallways.

Hallways must have a minimum horizontal dimension of 28 inches measured from the interior finished surface to the interior finished surface of the opposite wall. For manufactured homes with 14 feet of inside width or more, hallways must have a minimum horizontal dimension of 30 inches measured from the interior finished surface to the interior finished surface of the opposite wall. When appliances are installed in a laundry area, the measurement must be from the front of the appliance to the opposite finished interior surface. When appliances are not installed and a laundry area is provided, the area must have a minimum clear depth of 27 inches in addition to the 28 inches, or 30 inches for manufactured homes with 14 feet of inside width or greater, required for passage. In addition, a notice of the available clearance for washer/dryer units must be posted in the laundry area. Minor protrusions into the minimum hallway width by doorknobs, trim, smoke alarms or light fixtures are permitted.