The total run of a stairway can be defined as which quantity?

• A. The sum of the tread run
• B. The sum of the riser heights
• C. The sum of the tread width
• D. The number of treads

Answer: (A)

The total run of a stairway refers specifically to the horizontal distance that the stairs cover. This is determined by the sum of the tread run, which represents the horizontal portion of each step where a person places their foot. Each tread contributes to the overall horizontal span of the staircase, and thus, when you calculate the total run, you are essentially adding together the depth of all the treads.

The other options do not capture this concept accurately. The sum of the riser heights pertains to the vertical distance of the stairs, not the horizontal distance. The sum of the tread width could suggest individual widths but does not clearly represent the collective horizontal space occupied by the stairs. Lastly, the number of treads gives an idea of how many steps are present but does not address the total horizontal run. Therefore, the first option accurately reflects the definition of the total run of a stairway.