Mezzanine Stair Require Gypsum Underneath?

3/10/2022

I have an S-1 occupancy. It is a privately owned storage unit (no public access) used for the storage of exotic cars, maybe 3 vehicles in total. The space is about 1,400 square feet, and is fire sprinkler protected. There is a wood-framed mezzanine at the back of the unit as is about 300 square feet.

The question that has come up is if the underside of the open wood stairs to the mezzanine needs to be protected with fire-retardant gypsum board?

There is no sprinkler coverage under the stairs. The mezzanine may be built out by the owner to have a few chairs, a couch, a television, etc.

Digging into the code talks a lot about accessibility but not so much about the fire resistance requirements for the stairs. I have the found following in the 2015 IBC (code we are under):

1104.4 Multistory buildings and facilities. At least one accessible route shall connect each accessible story and mezzanine in multilevel buildings and facilities.

Exceptions
1. An accessible route is NOT required to stories and mezzanines that have an aggregate area of not more than 3,000 square feet (278.7 m2) and are located above and below accessible levels. This exception shall not apply to:

...and...

4. Where a two-story building or facility has one story or mezzanine with an occupant load of five or fewer persons that does not contain public use space, that story or mezzanine shall not be required to be connected by an accessible route to the story above or below.

So...the accessibility issue is covered but nothing about the rating of the stairs that I can find. Any help would be appreciated. Maybe I am not looking in the correct code section.

Thank you!

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8 Comments

Pete H.

3/10/2022 07:13:38 am

Okay, beyond IBC, what nfpa standard were the sprinklers in the building installed? I'm assuming NFPA 13 (I'm using 2016 edition, but I think you might be in 2013 due to your edition of IBC being 2015, so you may want to check that). because despite being private, this hasn't been described as residential.

(If residential sprinklers are used in NFPA 13, please refer to 8.10.6.3.2 and 8.10.7.3.2 in the 2016 edition which call for sprinklers under all fixed obstructions over 4'-0" wide, such as stairways)

NFPA 13 also guides for 8.15.3.1 (the section on combustible construction, assuming the wood is combustible) that sprinklers shall be installed beneath all stairways of combustible construction.

Jesse

3/10/2022 09:05:40 am

The lack of protection under the stairs combined with the lack of a fire barrier is concerning. I would imagine the stair way creates a shielded area to ceiling level sprinklers - and would continue to do so even if gypsum was installed.

Alex

3/10/2022 09:06:02 am

Hi,

From the question, there is not enough information to answer if you're permitted to have a combustible stairwell according to the IBC. That will drive your primary question regarding adding gypsum to the bottom side of the stairwell.

Although, I wanted to point out the following:

NFPA 13 (2013) 8.15.3.1 states that sprinklers must be installed beneath stairways of combustible construction.

NFPA 13 (2013) 8.10.6.3.2 states that sprinklers must be installed under fixed objects over 4'-0", such as stairs.

Either way, depending on the overall width, you may need to install sprinklers beneath the stairwell.

Todd Wyatt

3/10/2022 09:36:30 am

The adopted IBC (or IRC) is the starting point to determine the scoping requirements of the automatic sprinkler system (ASPS) per the "addition" of the mezzanine. You referenced the 2015 IBC.

The first issue to address is whether the 2015 IBC or the IRC (International Residential Code) is applicable. Per the 2015 IRC, "Garages and Carports" are addressed in Section R309. R309.5 Fire Sprinklers includes requirements for "private garages". If the garage-in-question is an "accessory building" ("a structure that is accessory to and incidental to that of the dwelling(s) and that is located on the same lot") to a single-family dwelling, I would recommend you clarify with the building official IF the 2015 IRC should be used (instead of the 2015 IBC) to evaluate the ASPS requirements for this garage.

I will continue as if the garage is to be evaluated per the 2015 IBC.

The second issue to address is to verify the Occupancy Classification (OC) of the private garage. You state that it is a "Group S-1 Storage Moderate-hazard". The IBC classifies "private garages" as a "Group U Utility and Miscellaneous" OC. In addition, Section 406.3 Private garages and carports limits the area to 1000 sf. Perhaps the building official required the "S-1" classification since it exceeded this area limitation? Maybe the jurisdiction allows larger private garages? I would recommend you clarify with the building official the correct OC and if it meets their requirements. Determining the correct OC is crucial since automatic sprinkler system (ASPS) requirements are dictated by the IBC Chapter 9 while the referenced standard NFPA 13 (13R) determines HOW the ASPS is to be designed, installed, tested, and maintained.

Next, review the ASPS requirements for both S-1 and U Occupancy Classifications. 903.2.9 Group S-1 requires ASPS if the fire area exceeds areas (12K, 24K, 5K) or if the fire area exceeds a number of stories (3). Based on this section, an ASPS is not required by the IBC for this S-1 OC “private garage.” Group U buildings are not required to be sprinklered per IBC Ch 9. While an ASPS may not be required for this “private garage” based on its OC, the installation of the ASPS is required to be compliant if it is part of the design.

The planned “mezzanine” may includes a “change of use” since it is adding a non-storage use in this (existing) private garage. This may be considered a “Change of Occupancy” (e.g. nonseparated multiple OC) so I recommend verification from the building official on how they interpret this non-storage use from an OC standpoint. Since this use occurring on a mezzanine (300 sf) is more than 10% of the 1400 sf garage, it may not be considered “accessory”.

Requirements for mezzanines are per 505.2 which requires the mezzanine cannot be more than 1/3 the floor area (1300/3 = 433 > 300 = Compliant), the Means of Egress meet Ch 10 (see 1004.11.2 & 1009.1), and meets the “openness” requirements of 505.2.3 (compliant?).

You state that the mezzanine is “wood-framed” but you did not identify the Type of Construction (I-V?) for the rest of the garage (non-combustible vs combustible?). If the garage is of noncombustible construction (Type I or II), combustible materials are permitted per Section 603 but a wood-framed mezzanine and stairway is not listed. The stairway is required to be “consistent” with the Type of Construction of the building per 1011.7. The code official should also be conferred when determining the calculated Occupant Load for the mezzanine’s intended use. The “accessibility” requirements you cited for the mezzanine relates to “accessibility for individuals with disabilities” per the ICC A117 (and ADA).

I am sorry if this created more questions than answers but this pathway through the Codes and the associated building officials is recommended to determine compliance.

Gregg Peterson

3/10/2022 01:14:27 pm

Thank you (and other commentators) for your in-depth research.

To answer some of your questions:

A.) The building is concrete tilt-wall construction with a steel joisted roof and a metal roof deck.

B.) Building official classified the units as S-1 as they were permitted as storage units and they wanted to cover the higher hazard category. The units are being marketed to private owners as collectible car storage areas and anticipated that minor repairs and vehicle work may be done. Thus, any S-1 activity was approved. No residential use is authorized. The maximum occupant load allowed by code is 24, but in reality this number is going to much smaller than that.

C.) The sprinkler system (NFPA 13 -2013) is provided throughout with complete coverage at the roof deck as well as under the wood framed mezzanine, but not under the open, wood-framed mezzanine stairs.

D.) The mezzanine is less than 1/3 of the floor area and the occupant load of the mezzanine will be about 3 or 4 persons. The code only allows for 1, but the mezzanine is not a a permanently occupied space, only for occasional use.

E.) It seems at this point requiring the stairs to be enclosed (type-X gypsum board) with no storage allowed under them seems to be the best course of action, unless they provide sprinkler protection under the stairs.

F,) The owner of the center apparently installed the basic wood-framed mezzanine as a sales tool and is leaving it up to the individual owners if they want to finish out the mezzanine or not with upgraded materials.

Little Fire Squasher

3/10/2022 04:04:01 pm

Here are some things that might trigger sprinkler:

Per 2013 NFPA 13 section....

8.9.5.3.2 Sprinklers shall be installed under fixed obstructions over 4' wide.....

8.15.3.1 Sprinklers shall be installed beneath all stairway of combustible construction.

If they decide to make the stairs non-combustible then..

8.15.3.2.3 Sprinklers shall be installed beneath landings or stairways where the area beneath is used for storage.

3/14/2022 09:14:14 am

A. Unless the steel joists include Sprayed Fire-Resistive Material (SFRM), the Type of Construction is probably Type IIB Noncombustible, Nonprotected.

B. The calculated Occupant Load based on the planned use of the space must be considered when evaluating the Means of Egress capacity for compliance. Owner frequenlty tell me that this space will "never have that many occupants" ... until I attend the ribbon-cutting ceremony where that calculated occupant load is met (and sometimes exceeded).

C & F. The owner cannot "install" a wood mezzanine & stairway without the required plan review and inspection by a building official since this alters the initial approved building. Adding a wood mezzanine and stairway into a noncombustible, nonprotected structure may alter the approved Type of Construction. Adding a mezzanine without a professional fire protection engineer's review is not permitted.

3/14/2022 03:59:18 pm

Thank you to everyone for the well-though out responses. This forum is truly one of the web's best resources...and Todd, received some more information on Friday that any owner driven modifications will need to be reviewed and permitted, including any upgrades to the open wood framed stairs and mezzanine that were previously approved for the "shell" space.

Mezzanine Stair Require Gypsum Underneath?

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