When corridors are provided, Section 1020.1 of the International Building Code (IBC) establishes the required fire resistance rating of corridors within buildings and structures subject to the IBC.
The purpose of a corridor enclosure is the provide protection to occupants who travel through it as they make their way to an exit.
Before we get into the fire rating requirements of corridors, let us see how the IBC defines a corridor.
CORRIDOR – An enclosed exit access component that defines and provides a path of egress travel.
Chapter 10 of the International Building Code (IBC) provides minimum requirements for designing the Means of Egress system in all buildings and structures.
The primary purpose of this is to establish a method of protecting people in buildings from the presence of a fire. The means of egress system for a building or structure provides a way of travel for occupants to escape while avoiding a fire.
A Means of Egress system has 3 parts to it: (1) Exit Access, (2) Exit, (3) Exit Discharge.
Based on the definition of a corridor we can see that it serves as an egress access component making it part of the means of egress system within the building. This is why the code regulates it.
Now going back to the corridor section in 1020.1, the code requires a level of protection though fire rated construction since the corridor serves as an egress component and is providing a path of egress travel to an exit during a fire.
Minimum Fire Rating for Corridors
The code outlines the required fire resistance rating in hours with Table 1020.1 and is based on 3 factors:
- Occupancy Group Classification
- Total Occupant Load Served by the Corridor
- Whether or not a Fire Sprinkler System is provided
We can see all these factors in Table 1020.1 below.
The above table will give us the required fire resistance rating the corridor must be based on a few factors. Lets take a look at the first column of the table.
The first column lists the occupancy. Here you will find every and all occupancy classification listed in the code.
The second column lists the occupant load that the corridor serves. When we see the word ‘All’ this means any amount of occupants that the corridor serves. Then we see the words ‘Greater than…’ which means the number of occupants serving the corridor must be greater than the number shown for the corridor to be rated. If the number of occupants serving the corridor is less than the number in this column, then the corridor is not required to be rated regardless if the building is sprinklered or not.
The third column of the table is split into two columns. This column specifies the minimum required fire-resistance rating (in hours) the corridor must be if it is required to be rated. You can see the rating requirement for buildings equipped throughout with an automatic sprinkler systems and for buildings that do not contain a sprinkler system.
If you see the words ‘Not Permitted’, the buildings classified as those occupancies indicated are required to be fully sprinklered meaning you cannot have these structures without a sprinkler system.
Now lets run through a quick example.
A fully sprinklered office building classified as a B occupancy has a single corridor that serves an occupant load of 60. What is the minimum required fire resistance rating of the corridor?
Based on Table 1020.1 a building classified as a B occupancy, with a corridor serving an occupant load greater than 30, requires a 0 hour rated corridor when the building is fully sprinklered, which means the corridor is not required to be fire rated.
An important note to make here is to always read the footnotes when applicable. You will notice the footnotes will provide additional information, give more clarity, or refer you to another section where an exception might apply.
Since this section requires corridors to be fire rated, what type of fire rated wall construction is required?
Without getting into much detail in this post, there are 3 general categories of a “Fire Rated Wall” outlined within the International Building Code. When we circle back to Section 1020.1, the code reads as follows:
Corridors shall be fire-resistance rated in accordance with Table 1020.1. The corridor walls required to be fire-resistance rated shall comply with Section 708 for fire partitions.
Section 708 will outline how the corridor wall must be built to be considered a fire partition.
Fun Tip: To learn more about Fire Rated Walls, be sure to check out this POST.
Exceptions to Fire Rated Corridors
Are there any exceptions to fire rated corridors?
In Section 1020.1, the code lists 5 exceptions where fire rated corridors are not required. Be sure to check out these exceptions first before you head over to the table.
Here are the 5 exceptions:
1. A fire-resistance rating is not required for corridors in an occupancy in Group E where each room that is used for instruction has not less than one door opening directly to the exterior and rooms for assembly purposes have not less than one-half of the required means of egress doors opening directly to the exterior. Exterior doors specified in this exception are required to be at ground level.
2. A fire-resistance rating is not required for corridors contained within a dwelling unit or sleeping unit in an occupancy in Groups I-1 and R.
3. A fire-resistance rating is not required for corridors in open parking garages.
4. A fire-resistance rating is not required for corridors in an occupancy in Group B that is a space requiring only a single means of egress complying with Section 1006.2.
5. Corridors adjacent to the exterior walls of buildings shall be permitted to have unprotected openings on unrated exterior walls where unrated walls are permitted by Table 602 and unprotected openings are permitted by Table 705.8.
In a Group E building, a fire rated corridor is not required when the room it serves is used for instruction or assembly purposes and where there is a door that opens directly to the outside. Specifically for rooms used for assembly, this exception requires half of the doors required for exiting to open to the outside.
For example if an assembly room requires 4 exits from that room, then at least 2 of them must open directly to the outside for the corridor to not be rated. For instruction rooms, at least one door is required to open to the outside.
Using this exception, the need for a rated corridor is eliminated since the rooms are provided with an alternative exterior exit.
In this exception corridors within dwelling/sleeping units in Group I-1 and R occupancies are not required to be rated.
This would be for example corridors within single dwelling units of apartments and townhouses, as well as sleeping units within hotel guestrooms, etc…
Since common corridors within apartment buildings would be required to be rated per the table, individual corridors within the dwelling unit itself would not.
Corridors located in open parking garages are not required to be fire rated.
In a Group B building, a fire rated corridor is not required were the space only requires one exit complying with Section 1006.2. Don’t get this confused with the main corridor of an office building. This applies to the corridor connecting individual suites where together do not require more than one exit.
There’s a lot going on in this exception since it references several other code sections but basically if the exterior wall of a building is also the wall of the corridor, the exterior wall is not required to be rated per the corridor provisions where the tables noted above do not require the exterior wall to be rated nor requires any protected openings.
To be clear the interior wall of the corridor is still required to be rated per Table 1020.1 but walls of the corridors adjacent to the exterior, being the actual exterior wall of the building, is not required to be rated if it complies with the conditions of this exception.
So this concludes the 5 exceptions for fire rated corridors.
For more information regarding corridor requirements, be sure to check out Section 1020 of the 2018 International Building Code.
* Reference Source – 2018 International Building Code – [Buy on Amazon]
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