What is the minimum fire resistance rating for the enclosure of floor openings connecting four or more stories in new construction?

What is the minimum fire resistance rating for the enclosure of floor openings connecting four or more stories in new construction?
A . 1 hour
B . 1½ hours
C . 2 hours
D . 2½ hours

View Answer

Answer: C

Explanation:

The minimum fire resistance rating for the enclosure of floor openings that connect four or more stories is governed by NFPA 101®, Life Safety Code®. According to NFPA 101 (2021 edition), Section 8.6.5.1, vertical openings (such as stairwells, shafts, and floor openings) connecting multiple floors in new construction must meet specific requirements to prevent the vertical spread of fire and smoke.

For openings connecting four or more stories, the fire resistance rating must be a minimum of 2 hours.

The reasoning for the 2-hour rating is to allow sufficient time for occupant evacuation and firefighting operations while maintaining structural integrity.

Floor enclosures are required to be designed with fire-rated construction that can contain a fire and limit its spread between floors.

1-hour ratings are typical for smaller vertical openings involving fewer floors.

2½-hour ratings are more stringent and often seen in specific high-risk areas or older construction requirements.

Reference: NFPA 101, Section 8.6.5.1: Fire resistance ratings for vertical openings in new construction.

NFPA 101 ensures that these ratings are consistent with safety objectives and risk levels posed by openings connecting multiple stories.