Spiral Stairs Building Regulations

Codes

• Though local and state authorities work independently, their building codes about spiral stairs may seem unusually similar. That is because they’re based on the International Residential Code, which was created by the International Code Council. Founded in 1994, this member organization ensures that the construction industry meets the same high criteria everywhere, and that methods for building, estimating and maintaining produce the same consistent, safe and durable structures. The organization also defines other standardized regulations such as the International Fire Code, the International Building Code and the International Existing Building Code.

Basics

• The 2012 International Residential Codes allows spiral staircases as both a mean of egress, or access between the exterior and interior of a residence, and as a way to connect floors at different levels. The width of the step at and below the handrail must be at least 26 inches. Each step must measure at least 7.5 inches deep as measured a foot from the narrower edge of the step, and must rise no higher than 9.5 inches from the adjacent lower step. The clear headroom measured from the top of each step must be at least 80 inches. Measurements must be consistent across the entire stairway.

Stairs

• Specifics not mentioned in the code for spiral staircases must follow the regulations mentioned for standard stairs. This includes the requirement for a handrail on at least one side of the stairs. It must be from 34 to 38 inches high, though it can exceed the maximum height if used as a transition from a handrail to a landing guardrail. The rail must be continuous for the full length of the stairs but must be at least 1.5 inches from any adjacent walls. Handrails with a circular cross section must have an outside diameter of between 1.25 and 4 inches. If it is not circular, it must have a perimeter measuring from 4 to 6.25 inches, with a maximum cross section of 2.25 inches.

Lighting

• Interior spiral stairways need a light at each landing that can illuminate the entire stair at not less than one foot-candle as measured from the center of steps and landings. Exterior spiral stairways need an artificial light at the top landing of the stairway. Artificial lights are not needed at the top and bottom landings of a stairway if an artificial light is located directly over the stairs.