Residential Building Inspector B1Building Planning and Life SafetyEasy
A residential building inspector is reviewing plans for a new single-family dwelling. The plans indicate a stairway with an open riser design. What is the maximum allowable opening between treads for this stairway?
- A8 inches
- B2 inches
- C6 inches
- D4 inches
Show answer & explanationAnswer & explanation
Correct answer: D. 4 inches
The IRC specifies a maximum opening between treads for open riser stairways to prevent a 4-inch sphere from passing through, which is a safety measure for children.
Why the other options are wrong
- A. This opening is significantly too large and would create a significant safety hazard.
- B. This opening is too small and not required by the code.
- C. This opening is too large and would pose a safety hazard, allowing a 4-inch sphere to pass through.
Open Riser Stairway Opening
For stairways with open risers, the opening between treads must be limited to prevent objects (specifically, a 4-inch sphere) from passing through, ensuring safety.
- Applies to open riser stairways.
- Prevents a 4-inch sphere from passing through.
- Ensures safety, especially for children.
Memory trick: Open risers need a '4-inch fence' to keep little ones safe.