Fireproofing for Column on Exterior of Exit Stair?

10/14/2024

This is a corner exit stair in a 2-story Type II-B building. There is 2-hr fire separation per client request (only 1-hr by code).

There's one column in the corner that only supports exterior precast walls and roof structure. Does it need to be fireproofed?

I would assume it doesn't. Any ideas? Thanks in advance.

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe

7 Comments

Glenn Berger

10/14/2024 08:09:37 am

Some fireproofing might be required. Need to see full detailing on how fire separation is being planned.

Todd E Wyatt

10/14/2024 08:23:03 am

This column meets the definition of Primary Structural Frame …

PRIMARY STRUCTURAL FRAME. The primary structural frame shall include all of the following structural members:
1. The columns.
2. Structural members having direct connections to the columns, including girders, beams, trusses and spandrels.
3. Members of the floor construction and roof construction having direct connections to the columns.
4. Members that are essential to the vertical stability of the primary structural frame under gravity loading.

… and per the building’s Type of Construction (TC), the fire-resistance rating (FRR) would either be 1-Hour (II-A) or 0-Hrs (II-B).

If the building is II-A, the FRR protection could be any tested/listed assembly that includes “individual encasement protection by protecting it on all sides for the full column height” :

IBC-2021
Chapter 7 Fire and Smoke Protection Features
Section 704 Fire-Resistance Rating of Structural Members
704.2 Column Protection
Where columns are required to have protection to achieve a fire-resistance rating, the entire column shall be provided individual encasement protection by protecting it on all sides for the full column height, including connections to other structural members, with materials having the required fire-resistance rating. Where the column extends through a ceiling, the encasement protection shall be continuous from the top of the foundation or floor/ceiling assembly below through the ceiling space to the top of the column.
Exception: Columns that meet the limitations of Section 704.4.1.

II-A includes the following keynotes :

b. In all occupancies, heavy timber complying with Section 2304.11 shall be allowed for roof construction, including primary structural frame members, where a 1-hour or less fire-resistance rating is required.
c. Except in Group F-1, H, M and S-1 occupancies, fire protection of structural members in roof construction shall not be required, including protection of primary structural frame members, roof framing and decking where every part of the roof construction is 20 feet or more above any floor immediately below. Fire-retardant-treated wood members shall be allowed to be used for such unprotected members.

Even if your building meets the “C” exception not requiring FRR protection of this column, the Interior Exit Stairway’s (IES) would require a 1-Hour FRR assembly per the scoping Code (e.g. IBC-2021).

IBC-2021
Chapter 10 Means of Egress
Section 1023 Interior Exit Stairways and Ramps
1023.2 Construction
Enclosures for interior exit stairways and ramps shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both. Interior exit stairway and ramp enclosures shall have a fire-resistance rating of not less than 2 hours where connecting four stories or more and not less than 1 hour where connecting less than four stories. The number of stories connected by the interior exit stairways or ramps shall include any basements, but not any mezzanines. Enclosures for interior exit stairways and ramps shall have a fire-resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours.
Exceptions:
1. Interior exit stairways and ramps in Group I-3 occupancies in accordance with the provisions of Section 408.3.8.
2. Interior exit stairways within an atrium enclosed in accordance with Section 404.6.
3. Interior exit stairways in accordance with Section 510.2.

Todd E Wyatt

10/14/2024 04:19:28 pm

The fire-resistance rating (FRR) requirements for ALL columns (e.g. Primary Structure) are determined by the Type of Construction (TC) of the building : either 1-Hour for TC II-A or 0-Hrs for TC II-B.

The FRR protection of the Interior Exit Stairway (IES) ... if that is what it is ... is determined by IBC Chapter 7 & Chapter 10.

Just because columns are located in a 1-Hr FRR-protected IES does not make them compliant per the Type of Construction requirements.

O.P.

10/15/2024 09:34:59 am

Thanks for your comment! Like I said, this is a TC II-B building, so no fireproofing of primary structure required. The column is fully contained within a 2HR egress stair enclosure (only required to be 1 hr by code). Getting different answers so far from the forum (thanks to all!!!)

Todd E Wyatt

10/16/2024 08:28:50 am

Thanks for the clarification ... I apologize for missing the II-B Type of Construction (TC) in your initial explanation.

Based on that, the columns are NOT required to be FRR protected per the TC.

The vertical 2-Hr FRR assembly (e.g. 2-Hr Fire Barrier : 2FB) used to protect the IES is required to extend horizontally to the Exterior Walls. These 2FBs are required to either be self-supporting OR supported by a 2-Hr Horizontal Assembly (2HA) which could include the Floor Construction (FC) for the 2FBs on Story 02 (and slab-on-grade at Story 01). If the latter strategy is used, the FC at Story 02 would be required to match the FRR of the 2FBs it is supporting. Likewise, the Primary Structure (e.g. columns & beams) supporting the 2-Hr FC would also be required to be protected by 2-Hr assembly(s).

The extent of the 2-Hr protection of Story 02’s FC and its supporting structure should be coordinated with the AHJ since it is not prescriptive. Some AHJs will require the structural bay supporting the IES’s 2FBs to be protected with 2-Hr assemblies.

Dan Wilder

10/14/2024 08:35:58 am

Not a building code guy however...

The fire resistance of the member would fall into Section 704 (2021 IBC) and 704.2 and 704.3 specifically for "individual encasement" (several other sections like Table 601).

Also, Section 704.10 states that load-bearing structural members which are located within the exterior walls or on the outside of a building or structure shall be provided with the highest fire-resistance rating, as determined by Table 601, for the type of building element or exterior bearing wall, or by Table 602 based on the fire separation distance.

I also looked back through some of our previous projects and all those stairwells that had columns within were enclosed, either individually or within a stair shaft. Finally, in the illustration I see that the two other columns that share the same stair shaft are enclosed (either for constructability or due to the IBC requirements) which, if allowed to follow the column in question would also not require the rated enclosure.

Jack G

10/14/2024 10:18:17 am

It needs to be enclosed like the other columns.

Fireproofing for Column on Exterior of Exit Stair?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES