The unit rise plus the unit tread in stair construction should equal what range in inches?

In stair construction, the combination of the unit rise (the vertical height of each step) and the unit tread (the depth of the step) is based on established guidelines to ensure safety and comfort when using the stairs. The standard range for the sum of the unit rise and unit tread is typically between 17 and 18 inches. This range helps to create stairs that are easy to navigate, minimizing the risk of trips or falls.

A unit rise that is too high, paired with a tread that is too shallow, can lead to stairs that are difficult to ascend or descend. Conversely, having a unit rise and tread that fall within this range facilitates a more ergonomic experience for users. Therefore, the answer that states the sum should equal 17-18 inches aligns with best practices in stair design, ensuring that they are functional and safe for everyday use.