In stair design, the combination of rise and run determines what key feature?

The combination of rise and run in stair design directly affects the angle or slope of the staircase. Rise refers to the vertical distance between two stair treads, while run refers to the horizontal distance from one step to the next. Together, these measurements create the stair's angle or slope, which is crucial for user safety and comfort.

An appropriate slope ensures that the stairs are easy to ascend and descend, minimizing the risk of accidents. If the rise is too high or the run is too short, the angle can become too steep, making the stairs difficult to navigate. Conversely, a gentle slope, resulting from a more balanced rise and run, creates a more comfortable stairway.

In contrast, the other options—width, height, and load-bearing capacity—do not directly derive from the relationship between rise and run. Width pertains to the side-to-side measurement of the staircase and affects the number of people who can use the stairs simultaneously. Height refers solely to the total vertical distance covered by the staircase, and load-bearing capacity relates to the materials used and the structural integrity of the staircase, which is influenced by factors unrelated to the rise and run alone.