Because the location of railings and balusters, width and depth of tread, and height of risers affect the ease and safety of using a stair, these dimensions are regulated by building codes. You must be sure that any stair you order will meet your local codes. Though many local codes have adopted national standards, there is no single national code for all areas. Some local codes have different restrictions than accepted standards. To find out about your local requirements, call your city or county building department.
The International Code Council, administered by the Building Officials and Code Administration (BOCA), allows maximum riser height of 7 3/4 inches and a minimum tread depth of 9 inches plus a 1-inch nosing where solid risers are utilized. These dimensions are a revision of earlier, briefly adopted standards that allowed a maximum of 7 inches on risers and a minimum of 11 inches for tread depths-sizing promoted by some saftety experts following a 1985 study of accidents on stairs in the workplace. Despite the fact that the steeper stairs are acceptable to many codes, some experts still believe they are prone to cause more accidents. Some builder organizations argue that these claims are yet to be proven and that 7-11 stairs take up more space and increase the costs of building them.
When ordering stairs that turn, such as spiral stairs, pay special attention to where measurements must be taken for code acceptance. Many codes demand a 9- to 10-inch tread depth (minimum) at a point 12 to 14 inches from the narrow side. You’ll also find restrictions on head-height clearance and railing construction and placement.
The key is to be sure that any stair you buy will not only meet codes but be an attractive, safe, easy-to-use addition to your home.