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Fire Rated Walls and Openings in Multifamily Residential Construction
What follows is a list of wall types commonly used in multifamily construction accompanied by information on the fire-resistance ratings for both the wall and any openings in the wall. I reference the 2018 International Building Code (IBC) as well as my local building code, the 2018 Seattle Building Code (SBC), which is just an amended version of the IBC. Note that smaller residential projects permitted under the International Residential Code (IRC) will have different requirements.
This is by no means an exhaustive list, and — as with all things related to the code— a summary such as this is no substitute for actually reading your local code and consulting with your local Authority Having Jurisdiction (AHJ).
This article explains how to determine the code-required fire rating of a given wall type. For actual assembly designs that meet the IBC’s fire resistance requirements, see my article Five Wood Frame Partition Assemblies for Multifamily Projects.
Egress Stairway Walls
Egress stairway interior walls must be fire rated per 2018 IBC 1023.2 and are considered fire barriers as defined by 2018 IBC 707. A 1-hour rated fire barrier is required for stairs connecting less than four stories, and a 2-hour rated fire barrier is required for stairs connecting four stories or more.
Per 2018 IBC Table 716.5, doors in egress stairway interior walls must be 60-minute rated where located in a 1-hour fire barrier and 90-minute rated where located in a 2-hour fire barrier.
Per 2018 IBC 1023.7, egress stairway exterior walls are treated differently than egress stairway interior walls. Exterior walls are required to be rated per the provisions of 2018 IBC 705. See “Exterior Walls” section below.
Also note that 2018 IBC 1023.7 requires a fire rating for some exterior walls that are in the vicinity of an egress stair’s exterior walls. If the egress stairway’s exterior walls are nonrated or if they contain any unprotected openings, then nearby walls that are within 10' (and not in the same plane as the egress stairway’s exterior wall) also need to be protected. See 2018 IBC 1023.7 for more detail.
