Spiral Stairs Building Code

Sources

• Though local, state and some federal building authorities specify building codes for private residences, they generally base it on the International Residential Code or IRC. The International Code Council, a member organization, created and updates this code so the construction industry and their jurisdictions can follow a safe and consistent standard. Variations on these standards do exist, such as those defined by the Americans with Disabilities Act, which apply only to commercial establishments or to homeowners who want their residences to be handicap accessible.

Specifics

• The 2011 IRC defines the specifics of spiral staircases through code R311.7.10.1. It mandates that the minimum clear width of treads under the handrail be at least 26 inches. Each step or tread must have a minimum depth of 7.5 inches as measured at 12 inches from the narrowest edge. Risers, which represent the vertical distance between adjacent steps, must be no higher than 9.5 inches. The headroom between a tread and the surface directly above it must be 78 inches or more.

Stairs

• Standards not mentioned in R311.7.10.1 must follow R311.7, which lists the rules for all stairway types. For example, all staircases must have a floor or landing at the top and bottom of each stairway. However, this is not required at the top of an interior flight of stairs, if no door swings over the stairs. Handrails are needed on at least one side of the staircase, if it has four or more steps. They must be between 34 and 38 inches as measured from the sloped plane next to a tread.

Lights

• Code R303.7 specifies that all interior and exterior staircases, including spiral versions, have lighting for the landings and treads. An artificial light source must be next to each stairway landing and must illuminate the center of the tread at one foot-candle or more. Exterior stairways must have an artificial light source at the top landing of the stairway. If an artificial source is located directly over a stairway section, then one is not needed at the top and bottom landing.