Regulations for House Stairs

IBC

• If regulations for house stairs at the local, state and some federal levels seem suspiciously similar, it’s because they all directly, or with some modification, come from the IRC or International Residential Code for One- and Two-Family Dwellings. Established in 1994, the non-profit International Code Council created and continuously refine this standardized set of coordinated codes based on many years of experience. The rules ensure that houses built in any part of the country are equally durable and safe. The organization also defines separate codes for plumbing, fire safety, energy conservation and property maintenance that have come into wide use.

Basics

• Stairways must be at least 36 inches wide at all points from the stair step up to the required minimum headroom height of 80 inches. Handrails must be less than 4.5 inches on either side of the stairway. If only one handrail is present, it must not reduce the clear width of each step under the rails to below 31.5 inches. If two handrails are available, the minimum clear width must be 27 inches. A single flight of stairs cannot rise more than 12 feet between floor levels or landings.

Steps

• The height of a riser between adjacent steps must be a maximum of 7.75 inches. The height must be constant across the entire stairway, with a variation of under 0.375 inches. Spaces between risers are allowed, as long as they do not allow a sphere measuring 4 inches in diameter to pass through. This prevents children’s heads from being stuck in such areas. A step, more commonly called a tread, must have a depth of 10 inches or greater. The depth cannot vary by more than 0.375 inches among an entire flight of stairs.

Disabilities

• The Americans with Disabilities Act uses the IRC as a foundation for defining stairs the handicapped use in commercial structures. These standards are optional for residences, but can prove useful for homebuilders who want to appeal to the ADA market. Many of the standards are the same, such as the measurements of stair widths, head clearances, treads and risers. One difference is that open risers are not allowed on ADA stairs. Another is the requirement for a handrail on either side of the stairs. A third difference is that the gripping surfaces of ADA rails must be between 1.25 to 2.25 inches. Standard rails can range from 1.25 to 1.5 inches.