Building codes for stairways include tread code, riser code and handrail code, according to SFGate. The source for theses codes is the International Building Code book, and they help to prevent stairway users from injuries by ensuring that the dimensions of various stairways are similar. The codes also ensure that the stairways contain typical features such as handrails for safety.
The tread code requires all the staircase treads, which are staircase sections that come in direct contact with the feet, to be evenly deep, with the standard depth dimension of 11 inches or more, notes SFGate. In case of a difference in the depth of various treads of a staircase, the difference should not exceed 0.375 inches. The riser code, on the other hand, requires each stairway riser to have a height of 4 inches or more, but not to exceed 7 inches. Exceptionally, the maximum height for a riser in townhouses and single-family houses is 7.75 inches. Just like the treads, the difference between the highest and the lowest riser should be 0.375 inches or less.
Although handrails are not necessary for single-step stairways, the handrail code requires all stairways with two or more steps to have a handrail, states SFGate. Although one handrail on one side of the staircase may be enough, a staircase can have a handrail on each side depending on convenience.