What is the required fire rating for a door in a 2-hour rated stairway?

In a 2-hour rated stairway, the required fire rating for a door is indeed 1.5 hours. This is based on the need to maintain the integrity of the exit stair enclosure during a fire, while also allowing for the protection of occupants who may be using the stairway as an exit route.

The rationale behind specifying a 1.5-hour fire rating for a door in a 2-hour rated stairway lies in the fire protection strategy which aims to effectively contain fire and smoke and protect egress paths. The door’s fire rating should be less than the rating of the assembly it protects—this means that while the stairway itself has a 2-hour rating, the door only needs to provide adequate resistance for 1.5 hours.

This ensures a balance where the door is still effective in maintaining the safety of stairway egress during an emergency without being overly robust, which could complicate safety regulations and construction requirements. Thus, the 1.5-hour requirement reflects a critical aspect of fire safety design in buildings.