R-2 Building with S-2 Tuck Under parking - NFPA 13 or 13R?

[Amber]

I work for a firm that does a lot of multi-family projects, often times with tuck under parking. We typically classify the parking as S-2, although in some cases have classified it as U. The question of whether to do a NFPA 13 or 13R system always comes up and no one in the office has a very good handle on which system to use. I've always used 13, because it is the safe bet and I thought that the building included S-2, so the NFPA 13R system couldn't apply to the building. Usually it is the contractor who asks why we aren't doing a 13R system. What are your thoughts on which system to use?

 

[cda]

Depends some on how many stories

And any trade offs

Plus what the ahj wants

Wiggle wiggle wiggle answer

Should be some better ones coming up

 

[RLGA]

I have received confirmation from NFPA in the past that a building used primarily for residential purposes is permitted to use the NFPA 13R system throughout--even for parking and other public mixed-use spaces. You cannot mix NFPA 13 and 13R systems in the same building. If you're using the horizontal separation allowance per IBC Section 510, you must use a NFPA 13 system in the building below the horizontal separation, but a NFPA 13R system could be used for the residential building(s) above the horizontal separation.

 

[cda]

NFPA 13R: DOCUMENT SCOPE
1.1* Scope. This standard shall cover the design and installation of automatic sprinkler systems for protection against fire hazards""""

in residential occupancies up to and including four stories in height in buildings not exceeding 60 ft (18 m) in height above grade plane. """"

A.1.1 NFPA 13R is appropriate for use as an option to NFPA 13 only in those residential occupancies, as defined in this standard, up to and including four aboveground stories in height, and limited to buildings that are 60 ft (18 m) or less in height above grade plane, which is consistent with limits established by model building codes for buildings of Type V construction. The height of a building above grade plane is determined by model building codes, which base the height on the average height of the highest roof surface above grade plane. For further information on the building height story limits, see model building codes. It is the intent of this standard that if NFPA13R is appropriate for use, it be used throughout the entire building. It is recognized that an accessory or incidental occupancy to the operations of the residential occupancy might exist within that residential occupancy. Such accessory or incidental occupancy would be considered part of the predominant (residental) occupancy and subject to the provisions of the predominant (residental) occupancy by

 

[Paul Sweet]

Most parking garages are too large to be considered an accessory or incidental occupancy.

 

[steveray]

A common question is whether a mixed occupancy
building which contains a Group R occupancy could
still use NFPA 13R for the design. If one of the mixed
use occupancies would require a sprinkler system
throughout the building in accordance with NFPA 13,
then a 13R system would not be allowed. If, however,
the only reason a sprinkler system is being installed
is because there is a Group R fire area within the
building, then an NFPA 13R system would be an
appropriate design choice.

2012 IBC commentary....

 

[RLGA]

Most parking garages are too large to be considered an accessory or incidental occupancy.

The mention of "accessory" and "incidental" in the NFPA annex is not to mean "accessory" and "incidental" as defined/described by the IBC. If the main function of the building is residential and it includes mixed-use spaces, such as a restaurant, gift shop, offices, etc., then a NFPA 13R system is permissible.

 

[Builder Bob]

If the parking is generally reaidential i use, it is no more a hazard than a garage in a typical R-3 senario......i think a 13 r system should be allowed since most cars are not more tha 2500 poinds, ise propane fuel, or carry hazardous materials.....the down side is if a retirement communtiy and golf carts are used .,,,ireally believe that this is a designer optiona nd shoukd refkect the actualmintended fuel loads anticipated

 

[ETThompson]

Hi,

We have a similar situation and questions here, we have an open S-2 parking garage below, and 4 stories of R-2 apartments above. We’re proposing a 3-hour horizontal separation between the garage and the apartments. The contractor is asking if we could use a 13R sprinkler system in the residential apartments.

(we are under the 2017 Ohio Building Code, based on 2015 IBC. The above-building is VA construction)

According to 903.3.1.2 we can use a 13R system as long as we do not exceed 4 stories and 60 feet. Section 510.7 applies to open parking garages, and says the height and stories need to be measured from the grade plane. Would the open parking garage be considered a story? Our reading, based on the Commentary, is no, and therefore we still comply.

Our understanding is the open parking garage does not need to be sprinklered at all (not called for in Ch. 9, and implied in 406.5.4.

If we sprinklered the parking garage (13R) could we omit or reduce the 3-hour separation?

Can you confirm that our assumptions are right and we haven’t missed anything?

Thanks

 

[RLGA]

If you are providing a 3-hour horizontal assembly, why not use Section 510.2? Thus, the height in stories is based on the number of stories above the 3-hour horizontal assembly; and, the height in feet is based on the overall height from the grade plane.

Per IBC Section 903.3.1.2, the number of stories is measured from the horizontal assembly and not the grade plane, so you could use NFPA 13R for the four residential stories above as long as the overall height from the grade plane does not exceed 60 feet. An NFPA 13 system is still required for the parking area below the 3-hour horizontal assembly, which must also be of Type IA construction.

However, this all changed in the 2021 IBC, so take advantage of it now while you are still in the 2015 IBC.

 

[ETThompson]

Thanks for the helpful suggestions!

 

[ChrisCampbell]

I have received confirmation from NFPA in the past that a building used primarily for residential purposes is permitted to use the NFPA 13R system throughout--even for parking and other public mixed-use spaces. You cannot mix NFPA 13 and 13R systems in the same building. If you're using the horizontal separation allowance per IBC Section 510, you must use a NFPA 13 system in the building below the horizontal separation, but a NFPA 13R system could be used for the residential building(s) above the horizontal separation.R

Ron - where in the IBC or NFPA 13/13R are you prohibited from having both types of systems in the same building?

 

[RLGA]

Ron - where in the IBC or NFPA 13/13R are you prohibited from having both types of systems in the same building?

Maybe the black-and-white statement I made was a little over-simplistic. Technically, there is no direct prohibition from mixing systems. It is just that if you provide a building with a partial NFPA 13 system and the rest is per NFPA 13R, then what you have for the entire building is an NFPA 13R system.

Like anything else where a minimum standard or code is required, you can always exceed the standard or code. NFPA 13R is a less stringent standard than NFPA 13. Thus if you design for an NFPA 13R system, then you can exceed that and comply with NFPA 13 in certain areas where you want greater protection. Section 1.4 of NFPA 13R (Section 1.5 of NFPA 13) allows for "systems, methods, or devices of equivalent or superior quality..." etc. However, if the code requires NFPA 13 throughout or the building exceeds the scope of NFPA 13R (i.e., primarily non-residential, greater than four stories, or more than 60 feet in height*), then you cannot make certain areas of a building comply with NFPA 13R since that is a lower standard and would not meet the equivalency requirement in NFPA 13.

* The 2021 IBC restricts the use of NFPA 13R to buildings where the highest story's floor level is 30 feet or less above fire department vehicle access.

 

[ChrisCampbell]

Maybe the black-and-white statement I made was a little over-simplistic. Technically, there is no direct prohibition from mixing systems. It is just that if you provide a building with a partial NFPA 13 system and the rest is per NFPA 13R, then what you have for the entire building is an NFPA 13R system.

Like anything else where a minimum standard or code is required, you can always exceed the standard or code. NFPA 13R is a less stringent standard than NFPA 13. Thus if you design for an NFPA 13R system, then you can exceed that and comply with NFPA 13 in certain areas where you want greater protection. Section 1.4 of NFPA 13R (Section 1.5 of NFPA 13) allows for "systems, methods, or devices of equivalent or superior quality..." etc. However, if the code requires NFPA 13 throughout or the building exceeds the scope of NFPA 13R (i.e., primarily non-residential, greater than four stories, or more than 60 feet in height*), then you cannot make certain areas of a building comply with NFPA 13R since that is a lower standard and would not meet the equivalency requirement in NFPA 13.

* The 2021 IBC restricts the use of NFPA 13R to buildings where the highest story's floor level is 30 feet or less above fire department vehicle access.

Agreed. I would add though that if you have a separated mixed-occupancy building, you could provide an NFPA 13R system in the residential areas and an NFPA 13 in other occupancies (as long as there is not an applicable code requirement for an NFPA 13 system throughout, e.g. a high-rise building). This approach would still allow you to take advantage of the numerous code allowances in other sections of the code that depend on the building being sprinkler protected per NFPA 13 OR 13R (for example, reduction in egress width factors (1005.3), increase in common path allowance (1006), increase in exit remoteness (1007)).

 

[redeyedfly]

U occupancy garages are limited to 1000 sf. Must be some really small garages for multifamily.

13 or 13R usually comes down to allowable area/height/stories in which 13R is mostly the same as non-sprinklered. Unless the building is very small, 13R is usually not a viable option.

This has a pretty good summary of code differences between the systems: https://www.meyerfire.com/blog/difference-between-nfpa-13-13r-and-13d

 

[Brian 2]

Best way to view this is take the R out of the equation for a second. Would a fire sprinkler system be required in the tuck under parking if this was an office building above that wouldnt otherwise require sprinklers? If so, then you are looking at NFPA 13. As mentioned above, a U is limited in area; so you are looking at an S occupancy and open vs enclosed parking garages. If it can qualify as a U, then the residential building including tuck under would be NFPA 13R protected and the tuck under parking sprinklered as areas outside of the dwelling unit under provisions of 13R (NFPA 13 by reference). This is opposed to NFPA 13 required because of the S occupancy which would drive concealed spaces to be sprinklered; There is a subtle difference in 13 vs 13R in these instances.

 

[Jay Smith]

I’m trying to understand a similar aspect of this concept, too. I see mention of S-2, but the idea of assigning the garages an S-2 occupancy because it’s too large for Group U is gone in the 2018 IBC. All I see is it shall be classified as Group U. And it must be separated to comply with section 508. If I have a NFPA 13R sprinkler system in the 3 stories of apartments, this seems to mean the tuck under garages must be separated by 2-hour fire barriers. Is that really true?

 

[Jay Smith]

Clarification: When I said the garages must be separated by 2-hour fire barriers, I meant separated from the R-2 occupancy. I see the separation between garages is required to be 1-hour rated.

 

[redeyedfly]

I’m trying to understand a similar aspect of this concept, too. I see mention of S-2, but the idea of assigning the garages an S-2 occupancy because it’s too large for Group U is gone in the 2018 IBC. All I see is it shall be classified as Group U. And it must be separated to comply with section 508. If I have a NFPA 13R sprinkler system in the 3 stories of apartments, this seems to mean the tuck under garages must be separated by 2-hour fire barriers. Is that really true?

406.3.1 gives the 1000sqft maximum for U garages and it is still in the 2018 IBC.

508 only requires 2hr if the building is non-sprinklered, 1hr if sprinklered. Sprinklers are required in both S-2 and R-2. And, the separation is only required if you're treating is as a separated occupancy, in a podium that is rarely the case since it's IA and the areas are unlimited so separating occupancies is not useful.

13 or 13R depends on the height and area of the building.

 

[Jay Smith]

406.3.1 gives the 1000sqft maximum for U garages and it is still in the 2018 IBC.

508 only requires 2hr if the building is non-sprinklered, 1hr if sprinklered. Sprinklers are required in both S-2 and R-2. And, the separation is only required if you're treating is as a separated occupancy, in a podium that is rarely the case since it's IA and the areas are unlimited so separating occupancies is not useful.

13 or 13R depends on the height and area of the building.

Thanks for the reply. I’m thinking of a 3-story wood-framed Type VA building where one side of the ground floor is private garages. Group U is limited to 2 stories because the building doesn’t have NFPA 13 sprinkler systems throughout. The whole building is limited to 2 stories if I don’t have a 2-hour occupancy separation between the U and the R-2. Do you agree with that?

 

[wtravisl]

Thanks for the reply. I’m thinking of a 3-story wood-framed Type VA building where one side of the ground floor is private garages. Group U is limited to 2 stories because the building doesn’t have NFPA 13 sprinkler systems throughout. The whole building is limited to 2 stories if I don’t have a 2-hour occupancy separation between the U and the R-2. Do you agree with that?

Jay, I'm looking at something similar and am curious as to where you landed.
I was originally aiming for a long "dingbat" type apartment, more or less, but am running into the same issue you mentioned regarding U limitations. From your comment "limited to 2 stories with no 2hr sep between U & R2", it seems like you're applying 508 non-separated uses provisions to your building. I'm still working it out, but so far, it seems to me that 406 is written specifically as a modifier or 'override' to 508. As in, if you meet 406 U criteria for your garage(s), you need only comply with the U separation criteria for dwelling unit / garage, not table 508.4.
406.3.2 Separation [paraphrased]: For OTHER THAN private garages adjacent to dwelling units, comply with 508. For private garages & dwellings, see 406.3.2.1&2... these sections describe separation that's significantly less robust than 508.

So in my opinion, compliance with 406.3.2.1/2 = "separation". Table 508.4 note 'c' confirms this: "See 406.3.2"
It follows that you can utilize the 508.4 separated occ provisions. Your U parking is only 1 story, separate area calcs & stories for your R2...

Any feedback on this is appreciated. Thanks-

 

[Jay Smith]

Jay, I'm looking at something similar and am curious as to where you landed.
I was originally aiming for a long "dingbat" type apartment, more or less, but am running into the same issue you mentioned regarding U limitations. From your comment "limited to 2 stories with no 2hr sep between U & R2", it seems like you're applying 508 non-separated uses provisions to your building. I'm still working it out, but so far, it seems to me that 406 is written specifically as a modifier or 'override' to 508. As in, if you meet 406 U criteria for your garage(s), you need only comply with the U separation criteria for dwelling unit / garage, not table 508.4.
406.3.2 Separation [paraphrased]: For OTHER THAN private garages adjacent to dwelling units, comply with 508. For private garages & dwellings, see 406.3.2.1&2... these sections describe separation that's significantly less robust than 508.

So in my opinion, compliance with 406.3.2.1/2 = "separation". Table 508.4 note 'c' confirms this: "See 406.3.2"
It follows that you can utilize the 508.4 separated occ provisions. Your U parking is only 1 story, separate area calcs & stories for your R2...

Any feedback on this is appreciated. Thanks-

The situation I was considering is only garages that are not adjacent to dwelling units. Last time I saw the drawings for that building, the design team had the wall along the interior face of the garages shown as an occupancy separation. The spaces on the other side of the separation are residential, office and assembly areas.

 

[wtravisl]

The situation I was considering is only garages that are not adjacent to dwelling units. Last time I saw the drawings for that building, the design team had the wall along the interior face of the garages shown as an occupancy separation. The spaces on the other side of the separation are residential, office and assembly areas.

I understand - different uses=different separation requirements. Thank you.

 

[khsmith55]

I have received confirmation from NFPA in the past that a building used primarily for residential purposes is permitted to use the NFPA 13R system throughout--even for parking and other public mixed-use spaces. You cannot mix NFPA 13 and 13R systems in the same building. If you're using the horizontal separation allowance per IBC Section 510, you must use a NFPA 13 system in the building below the horizontal separation, but a NFPA 13R system could be used for the residential building(s) above the horizontal separation.

Agree. In addition, NFPA13R also addresses parking attached to and/or under the R Occupancy, so if you meet the requirements in 13R for parking your compliant.