Use 13, 13R, or Both, for Mixed M+R Occupancy?

9/22/2023

We have a rehab of a two story with a walk out basement where they are going to expand the basement level and make it mercantile with the two upper floors being R-2.

This is Type V-B construction and they are proposing to 1-hour horizontal to separate the mercantile from the R use. They are wanting to use the standpipes as their sprinkler risers.

My question is three-fold:
1. Can they sprinkler the entire building with 13R, or
2. Can they omit sprinklers completely in the mercantile if they separate from the R use by 1-hour (the mercantile by itself would not require sprinkler protection,
3. Can they sprinkler the mercantile with 13 and the R use 13R without a rated separation?

I am an AHJ and only wanting to require what the Code requires. I am having trouble deciphering the requirements.

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9 Comments

Max

9/22/2023 08:10:02 am

They would need 3 HR separation in order to mix 13 and 13R. Look up "pedestal buildings".

They should also have architect/engineer do a code analysis.
Building Codes will dictate the need for Fire Suppression system.

Regards.

Eric R

9/22/2023 08:36:22 am

If you are using the IBC as your building code then you should be able to do the entire building as 13R. The commentary in the IBC talks about this, but the general concept is that if the ONLY reason the building is required to have sprinklers is due to the R occupancy than 13R is allowed to be used.

This however is not an easy path to navigate, as it requires the architect to document that no other provisions or trade-offs for sprinklers are required. For example, the rating between the mixed occupancies would need to be 2-hour based on the building being "not-sprinklered" since the 1-hour rating reduction is based on the installation of a full NFPA 13 system.

The same reasoning will need to be checked against building heights and areas, egress path length, fire separations, etc... For all intents the building needs to considered not-sprinklered.

For your second question, you can not omit the sprinkler protection in the mercantile area unless you follow the provisions of the IBC that would categorize the M-area as an entire separate building. Both NFPA 13 and 13 require the "building" to be sprinklered throughout, although each standard has different requirements to meet their definition of throughout. You will need to have the M-occupancy protected using the "outside of dwelling unit" rules found in NFPA 13R. This will likely lead to the M area being protected at an Ord-II density, but wouldn't require outside hose allowance or protection of combustible concealed spaces.

For your third question. This gets a bit murkier as the IBC and NFPA aren't particularly clear on mixing systems inside a single structure. My personal opinion is that if the building is not separated to the extent that the areas can be considered distinct buildings than a single system type should be used for the whole building. ie, the building can either follow the code path to be allowed to use 13R or you're out of luck and the entire building needs to be 13. The one exception to this is following the 'pedestal building' arrangement that Max mentions, but that really isn't an option for retrofitting an existing building.

Dan Wilder

9/22/2023 08:58:21 am

Looking through the last couple projects' Code Analysis Sheets (Ref 2018 IBC/IFC), all showed 3-hour horizontal separations per Section 510 to allow 13 below & 13R above (separate building allowances). Those projects are a mix of parking below(S-2)/R-2 above, Restaurant/Business/Mercantile (B/M) below and R-2 above, or Lobby/Pool Area/BBQ areas (A-3) with R-2 above.

The one that does not (only carries a 1-hour separation) we are having to layout per 13 for all levels, no allowance for 13R,

The jobs have a mix of Type I-A, III-A, V-A so not directly matching your VB Construction Type, but Section 510 for Special Provisions dictate construction in all the cases.

Glenn Berger

9/22/2023 10:00:27 am

The first thing that is needed is what are the governing rules and regulations for where this project is located.

Todd E Wyatt

9/22/2023 11:21:01 am

Q1. Can they sprinkler the entire building with 13R, or
A1. No.

The scoping Code (e.g. IBC-2021) determines WHERE an automatic sprinkler system (ASPS) is required to be provide based on either the Occupancy Classification(S) (OC) (Sections 903.2.1 through 903.2.10) and/or "Specific Building Areas and Hazards" (903.2.11).

Group M Mercantile is required to be protected by an ASPS IF it meets any (1) of the (3) prescriptive requirements of 903.2.7.
Group R Residential is required to be protected by an ASPS "throughout all buildings with a Group R fire area."

IF the Group M Mercantile is required to be provided by an ASPS per 903.2.7, it is required to be protected per NFPA 13 per 903.3.1.1.
IF the Group M Mercantile is NOT required to be provided by an ASPS per 903.2.7 but the Owner still wants to provide an ASPS, it is still required to be protected per NFPA 13 per 903.3.1.1.

IF the Group R Residential meets ALL (4) parameters of 903.3.1.2, then the ASPS is PERMITTED (not required) to be protected per NFPA 13R per 903.3.1.2.
IF the Group R Residential does NOT meets ALL (4) parameters of 903.3.1.2, then the ASPS is REQUIRED to be protected per NFPA 13 per 903.3.1.1.

Q2. Can they omit sprinklers completely in the mercantile if they separate from the R use by 1-hour (the mercantile by itself would not require sprinkler protection,
A2. Yes.

The Occupancy Separation (OS) between a Group M Mercantile & Group R Residential is as follows :

2-Hour Fire Barrier (2FB) IF no ASPS
1-Hour IF ASPS is NFPA 13 (S = Buildings equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.1 ... NFPA 13)

Q3. Can they sprinkler the mercantile with 13 and the R use 13R without a rated separation?
A3. It depends ...

Chapter 5 General Building Heights and Areas references 903.3.1.1 (NFPA 13) 19 times and references 903.3.1.2 (NFPA 13R) 7 times. This chapter determines (3) "Allowables" (maximum Building Area, maximum Number of Stories, and the maximum Building Height) based on the building's Occupancy Classifications (Group M Mercantile & Group R Residential ... R-1, R-2, R-3, and/or R-4?) and if it is protected throughout by an ASPS (NFPA 13 or NFPA 13R).

IF the building meets these (3) Allowables and 903.2.7 Group M, the building could be protected by any of the following combinations :

A : Group M & Group R = NFPA 13
B : Group M = No ASPS, Group R = NFPA 13 (based on NOT complying with 903.3.1.2)
B : Group M = No ASPS, Group R = NFPA 13R (based on complying with 903.3.1.2)

Additional comments ...
You state "have a rehab of a two story with a walk out basement where they are going to expand the basement level and make it mercantile with the two upper floors being R-2".

This Project includes an "Addition" and an "Alteration" to an Existing Building so it will need to meet BOTH the adopted IBC and the adopted IEBC.
The "walk out basement" needs to be determined IF it is really a BASEMENT as defined by the IBC or is it a STORY? Review Grade Plane requirements.

You state "They are wanting to use the standpipes as their sprinkler risers."
Standpipe scoping requirements are per IBC Section 905 Standpipe Systems and the referenced standard is NFPA 14. WHERE Standpipes are required is per 905.3 Required Installations. Standpipes are not ASPS however. A ASPS engineer is required to design these (2) separate but related Fire Protection systems.

Todd E Wyatt

9/22/2023 11:21:29 am

REFERENCES

IBC-2021
Chapter 9 Fire Protection and Life Safety Systems
Section 903 Automatic Sprinkler Systems

903.2 Where Required

903.2.7 Group M
An automatic sprinkler system shall be provided throughout buildings containing a Group M occupancy where one of the following conditions exists:
1. A Group M fire area exceeds 12,000 square feet (1115 m2).
2. A Group M fire area is located more than three stories above grade plane.
3. The combined area of all Group M fire areas on all floors, including any mezzanines, exceeds 24,000 square feet (2230 m2).
903.2.7.1 High-Piled Storage
903.2.7.2 Group M Upholstered Furniture or Mattresses

903.2.8 Group R
An automatic sprinkler system installed in accordance with Section 903.3 shall be provided throughout all buildings with a Group R fire area.
903.2.8.1 Group R-3
903.2.8.2 Group R-4, Condition 1
903.2.8.3 Group R-4, Condition 2
903.2.8.4 Care Facilities

903.3 Installation Requirements
Automatic sprinkler systems shall be designed and installed in accordance with Sections 903.3.1 through 903.3.8.

903.3.1 Standards
Sprinkler systems shall be designed and installed in accordance with Section 903.3.1.1 unless otherwise permitted by Sections 903.3.1.2 and 903.3.1.3 and other chapters of this code, as applicable.

903.3.1.1 NFPA 13 Sprinkler Systems
Where the provisions of this code require that a building or portion thereof be equipped throughout with an automatic sprinkler system in accordance with this section, sprinklers shall be installed throughout in accordance with NFPA 13 except as provided in Sections 903.3.1.1.1 and 903.3.1.1.2.
903.3.1.1.1 Exempt Locations
903.3.1.1.2 Bathrooms

903.3.1.2 NFPA 13R Sprinkler Systems
Automatic sprinkler systems in Group R occupancies shall be permitted to be installed throughout in accordance with NFPA 13R where the Group R occupancy meets all of the following conditions:
1. Four stories or fewer above grade plane.
2. The floor level of the highest story is 30 feet (9144 mm) or less above the lowest level of fire department vehicle access.
3. The floor level of the lowest story is 30 feet (9144 mm) or less below the lowest level of fire department vehicle access.
4. The number of stories of Group R occupancies constructed in accordance with Sections 510.2 and 510.4 shall be measured from grade plane.

Chapter 5 General Building Heights and Areas
Section 508 Mixed Use and Occupancy

508.4 Separated Occupancies
TABLE 508.4 REQUIRED SEPARATION OF OCCUPANCIES (HOURS)

Group M Mercantile & Group R Residential = 2-Hours IF no ASPS
Group M Mercantile & Group R Residential = 1-Hour IF ASPS (S = Buildings equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.1 ... NFPA 13)
a See Section 420.

Chapter 4 Special Detailed Requirements Based on Occupancy and Use
Section 420 Groups I-1, R-1, R-2, R-3 and R-4
420.1 General
Occupancies in Groups I-1, R-1, R-2, R-3 and R-4 shall comply with the provisions of Sections 420.1 through 420.11 and other applicable provisions of this code.
420.3 Horizontal Separation
Floor assemblies separating dwelling units in the same buildings, floor assemblies separating sleeping units in the same building and floor assemblies separating dwelling or sleeping units from other occupancies contiguous to them in the same building shall be constructed as horizontal assemblies in accordance with Section 711.
420.4 Automatic Sprinkler System
Group R occupancies shall be equipped throughout with an automatic sprinkler system in accordance with Section 903.2.8.

Eric R

9/22/2023 11:52:39 am

Todd,

I'm going to have to respectfully disagree.

For Q1: Here is a more detailed blog post from MeyerFire in 2019 that mentions the specific point I made above about 13R being the allowable standard in mixed-use buildings: https://www.meyerfire.com/blog/when-can-i-use-nfpa-13r-part-i

for Q2: I don't agree that a basic 2-hour fire barrier overrides the requirements of both the IBC and NFPA stating that systems need to be installed "throughout buildings". Now there are a few occupancy classes in the IBC that instead limits the required protection of just the occupancy fire area, or lower level floors, but this language is not duplicated in NFPA. Furthermore, neither the R or M occupancy rules utilize this kind of language and both state throughout building. Since the IBC does have code paths that allow a single structure to be designated as distinct buildings then in those cases you could provide protection on as required for each "building".

I will add that this approach is limited in it's application since many mixed-use buildings wont comply with the height or area limits of chapter 5, or the occupancy specific area or occupant load requirements in chapter 9 if they aren't sprinklered per NFPA 13.

But for smaller renovated buildings (especially older single family homes on old-town main streets being converted to mixed use) this approach can significantly reduce the burden of getting these buildings protected and back into productive use for the community. And is a valuable tool to increase the overall % of protected buildings that otherwise might just sit unused due to the cost of a full commercial sprinkler system.

Todd E Wyatt

9/22/2023 12:01:37 pm

IF the Group M Mercantile is NOT required to be protected by an ASPS per 903.2.7, then a NFPA 13R is acceptable to be used for the entire building IF the Group R Residential meets 903.3.1.2.

Alex

9/29/2023 08:30:11 am

Working on a similar project at the moment. They need a 3 hour separation to go with 13/13R. If they do not provide the separation, while you are still a separated occupancy, you need to protect the entire building with 13.

Use 13, 13R, or Both, for Mixed M+R Occupancy?

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