For a wall rated at 4 hours, what should the appropriate door assembly rating be?

For a wall rated at 4 hours, the appropriate door assembly rating must match or exceed the fire-resistance rating of the wall. Therefore, a door assembly with a rating of 4 hours is suitable, as it will provide the same level of protection against fire spread and heat transfer for the time specified.

A door assembly rated for 3 hours, as mentioned, is insufficient for a 4-hour rated wall, as it does not meet the requirement to provide continuity of the fire-resistive barrier. The idea is to ensure that all components of the fire-rated separation—walls, doors, and other openings—maintain the same fire-resistance level to effectively contain a fire for the designated time.

Using a door assembly rated for 1.5 hours or 2 hours similarly falls short of the requirements necessary to maintain the integrity of a 4-hour wall. Hence, having a door assembly rated at 4 hours is essential to adhere to fire safety codes and regulations and maintain safety in the building design.