Stairs are one of the most code-regulated elements in residential construction because they are responsible for a significant percentage of household injuries. Understanding the code requirements prevents expensive redesigns and ensures safety.
Rise and Run
The individual rise of each step — typically 7 to 7-3/4 inches — combined with the tread depth determines how comfortable a stair is to walk. The ideal relationship is a rise of 7 inches and a run of 11 inches, which produces a stair with a total angle of about 32 degrees.
Headroom and Width
Minimum headroom of 6 feet 8 inches is required for the entire stair run. The minimum clear width is 36 inches. These dimensions feel cramped in new construction — going wider and taller makes the stair dramatically more comfortable to use.