Residential Building Inspector B1Wall Construction and Wall CoveringsHard
An inspector is reviewing a residential renovation project where a new interior non-load-bearing wall is being constructed. The wall will enclose a shaft for plumbing pipes extending from the basement through the second floor. What is the minimum fire-resistance rating required for this shaft wall where it passes through the floor assembly?
- A1/2 hour
- B1 hour
- C2 hours
- DNo rating required for non-load-bearing shafts
Show answer & explanationAnswer & explanation
Correct answer: B. 1 hour
According to IRC Section R302.5.1, shafts that extend through more than one story and are not contained within a dwelling unit must be enclosed with fire-resistance-rated construction. A minimum 1-hour fire-resistance rating is required, even for non-load-bearing shafts, to prevent vertical fire spread.
Why the other options are wrong
- A. 1/2 hour is generally insufficient for shaft enclosures spanning multiple stories.
- C. 2 hours is typically required for higher-risk scenarios or specific occupancy types, exceeding the minimum for a residential plumbing shaft.
- D. A fire-resistance rating is required for shafts penetrating multiple floor levels to prevent vertical fire spread, regardless of load-bearing status.
Shaft Wall Fire-Resistance Rating
Shaft walls enclosing plumbing or other penetrations that extend through more than one story in a residential building must have a minimum 1-hour fire-resistance rating.
- Applies to shafts not contained within a single dwelling unit.
- Prevents vertical fire and smoke spread.
- Rating is for the enclosure, not individual pipes.
Memory trick: A multi-story shaft needs 'One Hour' of fire resistance to protect the home.