CSLB General Building (B)Mechanical, Electrical, Plumbing CoordinationMedium
A contractor is comparing draft stopping to fire blocking. Which statement correctly distinguishes the two?
- ADraft stopping and fire blocking are interchangeable terms for the same requirement
- BFire blocking seals small concealed spaces like stud cavities; draft stopping subdivides larger concealed spaces such as attics and floor/ceiling assemblies
- CDraft stopping is used only in exterior walls; fire blocking is used only in interior walls
- DFire blocking is required only in commercial buildings; draft stopping is required only in residential buildings
Show answer & explanationAnswer & explanation
Correct answer: B. Fire blocking seals small concealed spaces like stud cavities; draft stopping subdivides larger concealed spaces such as attics and floor/ceiling assemblies
Fire blocking closes small concealed cavities (stud walls, floor/ceiling junctions), while draft stopping subdivides larger concealed spaces, such as attics exceeding a certain area, to slow fire and smoke spread across large hidden volumes.
Why the other options are wrong
- A. They serve related but distinct code purposes and are not interchangeable.
- C. Both apply to interior concealed spaces, not strictly exterior vs interior walls.
- D. Both requirements apply in residential construction under the CRC, not split by building type this way.
Fire Blocking vs Draft Stopping
Fire blocking seals small concealed cavities; draft stopping subdivides larger concealed spaces like attics to limit fire and smoke spread.
- Fire blocking: stud walls, floor/ceiling junctions, stair stringers
- Draft stopping: large attics and floor/ceiling assemblies over specified area thresholds
- Both limit unseen fire travel but at different scales
Memory trick: Small gaps get blocked, big attics get stopped.