CSLB General Building (B)Framing and CarpentryMedium
A framing crew is installing a new set of stairs. The total rise from the finished floor below to the finished floor above is 105 inches. The desired riser height is approximately 7 inches. What is the most appropriate number of risers and the resulting actual riser height (rounded to two decimal places) for this stairway?
- A15 risers, 7.00 inches per riser
- B17 risers, 6.18 inches per riser
- C14 risers, 7.50 inches per riser
- D16 risers, 6.56 inches per riser
Show answer & explanationAnswer & explanation
Correct answer: A. 15 risers, 7.00 inches per riser
To find the number of risers, divide the total rise by the desired riser height: 105 inches / 7 inches/riser = 15 risers. This results in an exact 7-inch riser height, which is within typical code limits (usually max 7-3/4 inches).
Why the other options are wrong
- B. 105 / 17 = 6.18 inches. This is a valid riser height, but 15 risers provides a more common 7-inch height with fewer steps.
- C. 105 / 14 = 7.5 inches. While 7.5 inches is a valid riser height, 15 risers provides an exact 7.00-inch height, which is ideal if possible.
- D. 105 / 16 = 6.56 inches. This is a valid riser height, but 15 risers provides a more common 7-inch height.
Stair Riser Calculation
The process of determining the optimal number of risers and their individual heights to distribute the total vertical rise of a stairway evenly and within code limits.
- Total Rise / Desired Riser Height = Approximate Number of Risers.
- Adjust number of risers to get an even, code-compliant actual riser height.
- Maximum riser height typically 7-3/4 inches, minimum 4 inches.
Memory trick: Rise and divide, then check your stride.