For stairs between two floors 8 feet apart, using a typical riser height of 7.5 inches, how many treads are required?

For stairs between two floors 8 feet apart, using a typical riser height of 7.5 inches, how many treads are required?

• A. 11
• B. 12
• C. 13
• D. 14

Answer: (C)

To cover the total vertical rise, you divide the total rise by the height of each riser. The building height is 8 feet, which is 96 inches. With a typical riser height of 7.5 inches, 96 divided by 7.5 equals 12.8. Since you can’t have a partial riser, you round up to 13 risers. Each riser corresponds to a tread, so you end up needing 13 treads to reach the second floor. Using 12 risers would only reach 12 × 7.5 = 90 inches, which is short of the 96 inches needed.

To cover the total vertical rise, you divide the total rise by the height of each riser. The building height is 8 feet, which is 96 inches. With a typical riser height of 7.5 inches, 96 divided by 7.5 equals 12.8. Since you can’t have a partial riser, you round up to 13 risers. Each riser corresponds to a tread, so you end up needing 13 treads to reach the second floor. Using 12 risers would only reach 12 × 7.5 = 90 inches, which is short of the 96 inches needed.