Final answer:
Stairway landings are typically required to be at least 36 inches deep and 22 inches wide, every 12 feet or less of vertical rise. These measurements cater to safety and usability, evolving from older guidelines that recommended less depth.
Step-by-step explanation:
Stairway landings are required to be a specific size for safety and building code compliance. Although the precise measurements can vary based on local building codes, a well-accepted practice for the depth of stair landings is that they need to be at least as deep as the stairs are wide, with additional safety considerations factored in for the vertical rise of the stairs. The referenced "older rule of thumb" of 5 diameters side-to-side and 7-8 diameters deep has evolved to suggest as much as 8 diameters side-to-side and 15 diameters deep to ensure sufficient room and safety for users.
Applying these principles and considering how the width and height of steps for a jogger is calculated, stair landings might typically be at least 36 inches deep (which is 3 feet and roughly corresponds to the depth mentioned in the 'older rule of thumb'), and 22 inches wide, to accommodate the stride and foot placement of a person. This dimension should be provided at every 12 feet or less of vertical rise to allow for appropriate rest and transition spaces.