Commercial Building Inspector B2Building EnclosureMedium
A commercial building inspector is reviewing the firestopping requirements for a curtain wall system intersecting a floor slab. According to IBC Section 715.4, what is the primary purpose of the firestopping material installed in the void between the edge of the floor slab and the curtain wall assembly?
- ATo prevent the passage of smoke and flames through the void.
- BTo provide structural support for the curtain wall at the floor line.
- CTo act as a vapor retarder between floor levels.
- DTo improve the acoustic performance between floor levels.
Show answer & explanationAnswer & explanation
Correct answer: A. To prevent the passage of smoke and flames through the void.
IBC Section 715.4 specifically addresses perimeter fire barrier systems for curtain walls. The primary purpose of firestopping (or a perimeter fire barrier system) in the void between a floor slab and a curtain wall is to prevent the passage of flame and hot gases (smoke) from one story to the next, maintaining the fire resistance rating of the floor assembly.
Why the other options are wrong
- B. Firestopping materials are not designed for structural support; that's the role of the curtain wall anchorage.
- C. While some firestopping materials might have limited vapor retarder properties, it is not their primary purpose, nor is it a code requirement for this application.
- D. Firestopping can offer some acoustic benefits, but its main purpose is fire and smoke containment, not sound attenuation.
Curtain Wall Firestopping
A fire-resistive system installed in the void between the edge of a floor slab and a curtain wall to prevent fire and smoke spread.
- Required by IBC Section 715.4 (Perimeter Fire Barrier Systems).
- Maintains the fire resistance rating of the floor assembly.
- Prevents vertical spread of fire and smoke between floors.
Memory trick: Firestopping's job: Stop the fire, stop the smoke.