Using the correct spacing in stairway construction ensures that the stairs are safe and comfortable for any user. The International Code Council sets important guidelines for minimum tread and width. These guidelines ensure that users can comfortably set their feet down and use stairs without danger. Handrail and banister dimensions must also be considered in stair construction.
Treads and Risers
Stair steps must have a tread height that can comfortably fit a person's foot and a width that allows for safe passage. The International Residential Code states that risers, which are the height of each step, cannot be more than 7.75 inches. Treads, or the run of the staircase, should be at least 10 inches wide to accommodate the average foot size. An example of a standard rise and run is 6-3/4 inches by 10 inches. These standards are different for large office or public buildings, which require a riser height between 4 and 7 inches and a tread of 11 inches.
Handrails are required for most stairways and help protect users from falls. In residential construction, stairways must have at least one handrail if there are more than three steps. Handrails must be set 30 to 34 inches above landings and tread noses -- the protruding edges on treads. The rail itself must be between 1-1/4 and 2 inches in width for ease of grip. The balusters or posts that support the handrail should be spaced 4 inches or closer together to prevent children from falling through them. Construct guardrails, which prevent users from falling off landings, at a height of at least 42 inches to satisfy building codes.
Planning a Stairway
Constructing a stairway begins with taking measurements of the total height and length of the stairs. Start from where the first riser will start and measure to the top of the landing. Divide this measurement by an ideal riser height of 6-3/4 inches. For example, a height of 120 inches divided by 6-3/4 equals 17-3/4 inches, which can be rounded to 18. You would need to install 18 risers, or steps, in this example. Maintain consistency in the dimensions of the risers and treads and avoid any variation greater than 1/4-inch.
There are additional codes and guidelines for safe stair construction in homes and public buildings. Ensure there is headroom of at least 80 inches between each stair step and the ceiling. Most stairs are built with "nosing" -- if this is the case, the nose should optimally extend 1-1/4 inches to provide a more comfortable tread. Steps should never have a slippery surface as this can create an extremely dangerous situation. Install a gripping surface to eliminate potential slip and fall injuries.