With all of the recent attention on fire door assemblies in residential occupancies, today’s Quick Question has come up several times:
How is the required fire rating for apartment entry doors determined?
This process can be followed for other types of fire doors as well, but I will use the apartment entry door as the example. Using the 2021 edition of the International Building Code (IBC), refer to Section 1020 – Corridors, and to Table 1020.2 – Corridor Fire-Resistance Rating. Section 1020 states:
1020.2 Construction. Corridors shall be fire-resistance rated in accordance with Table 1020.2. The corridor walls required to be fire-resistance rated shall comply with Section 708 for fire partitions. [refer to the code for exceptions]
The paragraph above determines the type of wall that is required – a fire partition – and Table 1020.2 shows the required rating of the corridor wall. This table addresses the various occupancy types, the occupant load served by the corridor, and whether or not the building is equipped with a sprinkler system.
Residential occupancies (Group R) are shown on 4th line of the table. When the calculated occupant load served by the corridor is more than 10 people, and the building has a sprinkler system (“without sprinkler system” is not permitted), the required rating of the corridor fire partition is either 1/2 hour or 1 hour depending on the type of sprinkler system that is installed.
Next, we refer to Section 716 – Opening Protectives, and to Table 716.1 (2) – Opening Fire Protection Assemblies, Ratings and Markings. This table shows each type of rated wall and the required rating of the fire door assembly. The required rating of an operable door is typically less than the required rating of the wall, because of the reduced fuel load adjacent to the door.
The image below is a very small portion of the table, showing only the lines for corridor wall fire partitions. For either a 1-hour or 1/2-hour corridor wall that is required to be a fire partition, the required rating of the fire door assembly is 20 minutes. For sidelight/transom assemblies in 1-hour corridor walls, the required rating is 3/4-hour (these are not common). Footnote “a” is related to fire-resistance-rated assemblies tested to ASTM E119.
Based on these two tables, opening protectives installed in Group R corridor fire partitions must be 20-minute fire door assemblies (with the exception of sidelight/transom assemblies in 1-hour walls). These assemblies must meet the requirements of NFPA 80 – Standard for Fire Doors and Other Opening Protectives, as well as the adopted codes.