Apartments (4-Unit) with Demising Walls as 13R?

9/12/2022

I have a project with four separate apartment buildings with 4-units in each building.

All buildings identified as R-3 Occupancy, Type V-B Construction, single story. There are demising walls between each unit that are 1-hour fire-resistance-rated including a 1-hour draft stop between each unit.

The Architect has noted on the approved plans, "Fire Sprinklers Per NFPA-13D".

My question #1: would NFPA-13D be allowed in these 4-unit buildings?

These are not townhome style zero lot line buildings built independent to one another. I think the project should be designed according to NFPA-13R.

Question #2: One building has a unit designated as a "Laundry room and folding room". I think this single unit should be designed according to NFPA-13 under Ordinary Hazard Group-1, correct?

Thanks in advance for your feedback!

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11 Comments

Pete H

9/12/2022 06:38:42 am

From the description it sounds like yes to both. However an AHJ might be willing to grant leeway on the 13D situation and let you use a two head calc rather than a four head calc (especially if no compartmented space actually has more than two heads within). But by the letter of the code and the description you've given, yes to both.

Alex

9/12/2022 07:49:37 am

Hi,

Question 1: From the description, this would fall under NFPA 13R. You could request the code approach used by the architect to get NFPA 13D but as the FPE, I would go 13R.

Question 2: Just to confirm, the entire unit will be treated as a laundromat with multiple machines? If this is the case, NFPA 13 A.4.3.3 states laundries fall under OH1.

Thanks,
Alex

Henry

9/12/2022 08:24:17 am

With a R-3 occupancy it would appear that they are using the IBC and not the IRC (which would allow the 13D)...dwelling unit separation is required to be 1 hour...and egress windows are required as well...the IBC allows for 13D systems in R-3 occupancies per 903.2.8.1

Barry Brainard

9/14/2022 01:16:35 pm

Each state may have amendments regarding this requirement. 2020 Minnesota Building Code amends per:
[F] 903.2.8.1 Group R-3. Where required by Section
903.2.8, Group R-3 occupancies shall be provided with an automatic sprinkler system that complies with Section 903.3.1.1, 903.3.1.2, or 903.3.1.3.

[F] 903.3.1.2 NFPA 13R sprinkler systems. Automatic sprinkler systems in Group R occupancies up to and including four stories in height in buildings not exceeding 60 feet (18 288 mm) in height above grade plane shall be permitted to be installed throughout in
accordance with NFPA 13R. The number of stories of Group R occupancies constructed in accordance with Sections 510.2 and 510.4 shall be measured from the horizontal assembly creating separate buildings.

[F] 903.3.1.3 NFPA 13D sprinkler systems. Automatic sprinkler systems installed in Group R-3 and R-4, Condition 1 occupancies shall be permitted to be installed throughout in accordance with NFPA 13D.

Michael Keith Bauer

9/12/2022 08:27:00 am

As an AHJ I would not accept the R3 designation. In the 2018 Building Code R3 is listed as "Buildings that do not contain more than two dwelling units". That would take the 13D out of the equation, and being it is really an R2 apartment house, a 13R would be acceptable. The one hour walls do not created separate buildings so the 4 units would be counted as part of the whole building. Just my two cents.

Roger Fast

9/14/2022 02:18:10 pm

Agreed, in addition "demising wall" is not a code defined term.

9/12/2022 08:31:13 am

We recently went through this deliberation with our Building Official, and the consensus based on the Florida Building Code is that 13R is required because they are not true townhomes with zero lot lines.

Todd E Wyatt

9/12/2022 08:33:45 am

SUMMARY
Verify the Occupancy Classification (OC) as the building should be classified as a R-2 and not a R-3.
R-2 OCs are required by the scoping fire Code (e.g. 2021 IBC) to be protected by an automatic sprinkler system (ASPS) meeting NFPA 13.
R-3 OCs are permitted by the scoping fire Code (e.g. 2021 IBC) to be protected by an automatic sprinkler system (ASPS) meeting NFPA 13D.

EXPLANATION
The scoping Code (e.g. 2021 IBC) includes prescriptive requirements for the automatic sprinkler system (ASPS) based on the building(s) Occupancy Classification (OC).

Group R-3 Residential is defined as follows :
310.4 Residential Group R-3
Residential Group R-3 occupancies where the occupants are primarily permanent in nature and not classified as Group R-1, R-2, R-4 or I, including:
Buildings that do not contain more than two dwelling units
Care facilities that provide accommodations for five or fewer persons receiving care
Congregate living facilities (nontransient) with 16 or fewer occupants
Boarding houses (nontransient)
Convents
Dormitories
Fraternities and sororities
Monasteries
Congregate living facilities (transient) with 10 or fewer occupants
Boarding houses (transient)
Lodging houses (transient) with five or fewer guest rooms and 10 or fewer occupants

Since this “apartment” building does not seem to meet one of these examples (e.g. “Buildings that do not contain more than two dwelling units”), the correct OC should be Group R-2 Residential.

310.3 Residential Group R-2
Residential Group R-2 occupancies containing sleeping units or more than two dwelling units where the occupants are primarily permanent in nature, including:
Apartment houses

Checking “Chapter 9 Fire Protection and Life Safety Systems” for ASPS for R-2 provides the following :

Section 903 Automatic Sprinkler Systems
[F] 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.
[F] 903.2.8.1 Group R-3
An automatic sprinkler system installed in accordance with Section 903.3.1.3 shall be permitted in Group R-3 occupancies.

R-2 are required to be protected by an ASPS meeting NFPA 13.
R-3 are permitted to be protected by an ASPS meeting NFPA 13D.

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

903.3.1.3 NFPA 13D Sprinkler Systems
Automatic sprinkler systems installed in one- and two-family dwellings; Group R-3; Group R-4, Condition 1; and townhouses shall be permitted to be installed throughout in accordance with NFPA 13D.

Jesse

9/12/2022 10:46:29 am

We have had instances where the AHJ has accepted these as 13D designs due to the fire wall.

Mike

9/12/2022 01:58:22 pm

According to the building code, what is a demising wall? Is it another way of saying rated?

9/13/2022 08:22:23 am

In this condition, the demising wall is the fire-resistive rated (FRR) assembly between adjacent "dwelling units." Per 2021 IBC, walls and floor assemblies separating dwelling units shall be 1-Hour FRR. The walls shall be 1-Hour Fire Partitions (1FP) and the floor construction shall be 1-Hour Horizontal Assemblies (1HA).

Apartments (4-Unit) with Demising Walls as 13R?

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