Stair Building Designs & Standards

Regulations

• Building codes at the local, state and sometimes up to the federal levels specify acceptable designs and standards for stair building. Only by following these designs can builders ensure that their constructions will obtain necessary approval from building inspectors. American codes generally follow the examples set by the International Residential Code or IRC, developed by the International Code Council. This member organization also specifies stair standards for commercial spaces through the International Building Code, as well as other regulations such as the International Fire Code and the International Property Maintenance Code.

Standard

• The 2012 IRC specifies that a standard flight of stairs must have a vertical rise of 12 feet or less between floors or landings. Stairways must be at least 36 inches wide at all points, with a minimum headroom of 80 inches from the top of the tread to the interruption directly above. Any handrails must project less than 4.5 inches on either side of the stair. They cannot allow the clear width of the stair to fall below 31.5 inches for one handrail or below 27 inches for two rails. The depth of the steps or treads must be 10 inches, and cannot vary by more than 0.375 inches across the entire flight. The risers, or vertical areas connecting one tread to the next, must be a maximum of 7.75 inches. They may have spaces between them, as long as a 4-inch-diameter, which is the size of a child’s head, cannot pass through.

Spiral

• Spiral staircases are ideal for small spaces because they do not require as much room as standard versions to traverse floors. They must have a clear width below the handrail of at least 26 inches. Each tread must be at least 7.5 inches deep as measured one foot away from the narrowest edge. This dimension must be identical across all treads in the stair. The maximum rise between treads is 9.5 inches. The minimum headroom is 78 inches. Any requirement not changed specifically for spiral stairways must follow the previously mentioned codes for standard stairs.

Bulkhead Enclosures

• Bulkhead enclosure stairways are exempt from these standards. These refer to stairs that are not required for building exits (because other means already exist) but allow people to enter from an outside grade, such as a lawn, to a basement. The maximum difference between the finished basement level to the outside grade must be eight feet or less. And the opening from the outside grade to the basement must be enclosed with hinged cellar doors or other allowable structures.