CSLB General Building (B)Mechanical, Electrical, Plumbing CoordinationMedium
A contractor is fire blocking a continuous interior partition wall that has an unbroken concealed stud space running 22 feet in length with no floor or ceiling level interruption. Per the California Residential Code, at what maximum horizontal interval must fire blocking be installed along this run?
- A8 feet
- B20 feet
- C6 feet
- D10 feet
Show answer & explanationAnswer & explanation
Correct answer: D. 10 feet
CRC fire blocking provisions require fire blocking horizontally at intervals not exceeding 10 feet in concealed spaces of stud walls, in addition to the vertical requirements at floor and ceiling levels. A 22-foot run would therefore need at least two horizontal fire blocks.
Why the other options are wrong
- A. 8 feet is not the code-specified maximum interval.
- B. 20 feet exceeds the maximum allowable interval and would leave excessive unblocked cavity length.
- C. 6 feet is more restrictive than the code requires.
Horizontal Fire Blocking Interval
In addition to vertical fire blocking at floor/ceiling levels, concealed stud spaces must be fire blocked horizontally at intervals not exceeding 10 feet.
- 10-foot maximum horizontal spacing in concealed stud cavities.
- Works alongside vertical fire blocking requirements.
- Prevents long unbroken fire/smoke travel paths within walls.
Memory trick: 'Ten feet, then block the heat.'