Can I use NFPA 13R in a Type V-A, R2 condos?

[goodwork]

We have a framed up condominium building, and the owner is requesting changing from NFPA13 to 13R, in order to avoid sprinklering cavities and taking advantage of the otherwise more lenient 13R system as a cost savings measure. Here's the situation:

• Code is based on IBC 2018
• 4 stories of Type V-A construction and R-2 occupancy (condominiums)
• above 2 levels of Type IA concrete podium (will remain NFPA13)

My questions:

1. To your knowledge, is this change allowed?
2. Will it trigger any other ratings, details, etc. that maybe we haven't considered at first glance?

Your expertise and guidance would be greatly appreciated.

 

[classicT]

Checks out at ok per Table 504.4 (S13R and S are both 4-stories max)
Area could be an issue per Table 506.2 (S13R 12,000sf max; SM 36,000sf max)

One aspect to be clear on, it is possible to use a 13R system only for the R-2 upper stories. The I-A podium would require the full 13 systems as you have indicated.

 

[Yankee Chronicler]

13R is intended for R-2 and R-3 type residential occupancies. Does your project meet all of the following requirements?

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.

The number of stories of Group R occupancies constructed in accordance with Sections 510.2 and 510.4 shall be measured from grade plane.

The podium creates an effective "ground plane" for the residential stories, but what are your floor-to-floor heights? The "lowest level of fire department access" is irrespective of the artificially-generated "ground plane" created by the podium. Assuming the lowest level of fire department vehicle access is going to be the lower level of the parking structure, if you have even 9 feet floor-to-floor the floor level of the second residential floor is going to be 27 feet above the lowest level of fire department access, the floor level of the third residential story will be 36 feet, and the fourth residential story will be 45 feet.

I don't see how you can possibly make it work.

 

[goodwork]

13R is intended for R-2 and R-3 type residential occupancies. Does your project meet all of the following requirements?



The podium creates an effective "ground plane" for the residential stories, but what are your floor-to-floor heights? The "lowest level of fire department access" is irrespective of the artificially-generated "ground plane" created by the podium. Assuming the lowest level of fire department vehicle access is going to be the lower level of the parking structure, if you have even 9 feet floor-to-floor the floor level of the second residential floor is going to be 27 feet above the lowest level of fire department access, the floor level of the third residential story will be 36 feet, and the fourth residential story will be 45 feet.

I don't see how you can possibly make it work.

Hi Yankee, what version of the code is this?

 

[goodwork]

Checks out at ok per Table 504.4 (S13R and S are both 4-stories max)
Area could be an issue per Table 506.2 (S13R 12,000sf max; SM 36,000sf max)

One aspect to be clear on, it is possible to use a 13R system only for the R-2 upper stories. The I-A podium would require the full 13 systems as you have indicated.

classicT, thanks for mentioning the area table limitation. The floor areas do exceed 12,000, but we have frontage increases for this building per 506.3 = 12,000 (506.2) + 18,000 (506.3) = 30,000. Does the increased allowable area get us into 13R territory?

 

[Jay Smith]

Are you going to be under the height limit of 60 feet above grade plane in 2018 IBC 903.3.1.2?

 

[goodwork]

Are you going to be under the height limit of 60 feet above grade plane in 2018 IBC 903.3.1.2?

Jay, we are under 60 feet as measured from the grade plane. (The lower garage is below grade.) Thanks.

 

[Yankee Chronicler]

Hi Yankee, what version of the code is this?

2021 IBC. 2018 is different:

[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.

 

[Yankee Chronicler]

Are you going to be under the height limit of 60 feet above grade plane in 2018 IBC 903.3.1.2?

Keep in mind that the whole concept of "podium" buildings is that the top/roof of the garage creates a new "grade plane" for the other building (residential, in this case) that sits on top of it. With that in mind, a 4-story residential building could probably be under 60 feet in height above the topmost elevation of the garage.

And that's probably why they revised this section from 2018 to 2021.

 

[Jay Smith]

Keep in mind that the whole concept of "podium" buildings is that the top/roof of the garage creates a new "grade plane" for the other building (residential, in this case) that sits on top of it. With that in mind, a 4-story residential building could probably be under 60 feet in height above the topmost elevation of the garage.

And that's probably why they revised this section from 2018 to 2021.

2018 IBC 510.2 lists area limitations, fire wall continuity, number of stories and construction type as the issues in which the buildings are considered to be separate. No mention of height. What code section indicates a new grade plane is allowed?

 

[Yankee Chronicler]

510.2 does mention height. Height is addressed in criteria number 6. But the concept of podium buildings was widely regarded as the top of the garage creating a new "grade plane" (at least that's the way architects in my corner of the universe discuss it), with the height of the upper building being regulated from that (which it was, in terms of number of stories). I haven't read the documentation for the change from IBC 2018 to IBC 2021, but I believe this section was revised to try to eliminate this potential confusion. The change to lowest level of fire department access makes it consistent with other sections of the code that are also concerned with height primarily as a function of fire fighter access.

 

[classicT]

classicT, thanks for mentioning the area table limitation. The floor areas do exceed 12,000, but we have frontage increases for this building per 506.3 = 12,000 (506.2) + 18,000 (506.3) = 30,000. Does the increased allowable area get us into 13R territory?

How did you calculate at 18,000sf increase per 506.3?

Per 506.2.3, you must use the NS value times the area factor increase which has a max of 75%. Therefore, 12,000 X 75% = 9,000sf increase (not 18,000sf).

Your allowable area is as follows:

[12000 + (12000 x .75) ] x 4 = 84,000sf allowable (each floor no more than 21,000sf)

You have not noted your floor areas, so I do not know if you are within the allowable.

 

[khsmith55]

13R is intended for R-2 and R-3 type residential occupancies. Does your project meet all of the following requirements?



The podium creates an effective "ground plane" for the residential stories, but what are your floor-to-floor heights? The "lowest level of fire department access" is irrespective of the artificially-generated "ground plane" created by the podium. Assuming the lowest level of fire department vehicle access is going to be the lower level of the parking structure, if you have even 9 feet floor-to-floor the floor level of the second residential floor is going to be 27 feet above the lowest level of fire department access, the floor level of the third residential story will be 36 feet, and the fourth residential story will be 45 feet.

I don't see how you can possibly make it work.

Great catch! I forgot they reduced the max. floor level to 30'. Note, this distance will be measured from FD access (i.e. grade +/-) NOT the Podium plate.