Coordinating the IBC and NEC definitions of "Building"

[wwhitney]

The 2023 NEC and the 2021 IBC have very similar definitions of "Structure":

2021 IBC "STRUCTURE. That which is built or constructed."
2023 NEC "Structure. That which is built or constructed, other than equipment."

The NEC added that last clause "other than equipment" in the 2017 version to clarify, for example, that if you run a feeder to a free-standing self-contained power pedestal set in the middle of a field, it is equipment only, therefore not a structure, and therefore does not require a grounding electrode system. [If you instead use a panelboard on a 4x4 post in the ground, it is still a bit ambiguous whether the 4x4 post is equipment or not; if not, that is a structure and would require a grounding electrode system.]

However, the 2023 NEC and 2021 IBC have very different definitions of "Building":

2021 IBC "BUILDING. Any structure utilized or intended for supporting or sheltering any occupancy."
2023 NEC "Building. A structure that stands alone or that is separated from adjoining structures by fire walls."

[Apparently the NEC is happy to call a flagpole or a human-scale sculpture a building, but the IBC does not wish to do that.] The main distinction the NEC is making between structures and buildings is that bit about firewalls. For the NEC a series of townhouses separated by firewalls would be one structure but multiple buildings; and so for example when 230.2 says in effect "one service per building," that automatically allows one service per townhouse without requiring any exception or other language.

My question is a basic one about the IBC, with which I'm not so familiar, particularly its fire requirements. What is the IBC equivalent term for the way the NEC is using the term "Building"? I.e. a portion of a structure which is separated by (sufficiently rated) firewalls?

Thanks,
Wayne

 

[north star]

% ~ % ~ %

Wayne, ...the IBC has always been the Code \ Standard by which structures \
bldgs. are defined........Regardless of what the NEC says, the IBC is the Code
definition to go by........Also, when using the IBC for definitions \
identification, the RDP of record should be the one to contact for clarity.
An electrical RDP would not typically design the structure \ bldg. \ other.
They [ typically ] design the electrical systems \ components that will be
installed in the structures \ bldgs.

% ~ % ~ %

 

[wwhitney]

Wayne, ...the IBC has always been the Code \ Standard by which structures \ bldgs. are defined.

Sure, as a general matter. But when applying the NEC, the NEC's explicit definition takes precedence.

My interest here is to submit a Public Input for the 2026 NEC to clarify its definition of "Building" (it's a bit sloppy right now) and to provide an Informational Note of the equivalent term in the IBC. So I'm just trying to find out what term the IBC uses that is closest to the NEC definition of "Building."

Cheers, Wayne

 

[north star]

# ~ # ~ #

O.K. !..........Please keep in mind that the RDP's that design a structure \
bldg., ...they are the ones that are responsible for the correct designation
( the Primary definition ).

The NEC would, IMO, ...need to follow the lead of the Primary definition.
As long as the readers of the NEC understand that the IBC is the Standard by
which things are defined..........I have had discussions with some electrical
contractors & general electricians-of-the-field start to describe a structure \
bldg., and use the NEC as their Standard..........I tried to correct their mindsets,
but the light bulbs never came on........They had "NEC tunnel vision" !

# ~ # ~ #

 

[steveray]

2 best sections I know of OTTOMH:

706.2 Structural stability. Fire walls shall be designed and
constructed to allow collapse of the structure on either side
without collapse of the wall under fire conditions. Fire walls
designed and constructed in accordance with NFPA 221
shall be deemed to comply with this section.

503.1 General. Unless otherwise specifically modified in
Chapter 4 and this chapter, building height, number of
stories and building area shall not exceed the limits specified
in Sections 504 and 506 based on the type of
construction as determined by Section 602 and the occupancies
as determined by Section 302 except as modified
hereafter. Building height, number of stories and building
area provisions shall be applied independently. For the
purposes of determining area limitations, height limitations
and type of construction, each portion of a building separated
by one or more fire walls complying with Section 706
shall be considered to be a separate building.

 

[wwhitney]

portion of a building separated
by one or more fire walls

Thanks!

So the IBC doesn't have a defined term that means exactly the above phrase? Whenever a section wants to specify the above, rather than an entire building, it has to use a phrase like that?

The NEC has basically just defined the word "building" to mean the above phrase, along with expanding it to cover any structure.

Thanks, Wayne

 

[steveray]

For H&A purposes....they are separate buildings.....for other purposes, not....And they are structurally independent, but sometimes considered one structure....Isn't code fun?

 

[Mr. Inspector]

[Apparently the NEC is happy to call a flagpole or a human-scale sculpture a building, but the IBC does not wish to do that.] The main distinction the NEC is making between structures and buildings is that bit about firewalls. For the NEC a series of townhouses separated by firewalls would be one structure but multiple buildings; and so for example when 230.2 says in effect "one service per building," that automatically allows one service per townhouse without requiring any exception or other language.

Townhouses are separated by Fire Partitions not Fire Walls.

 

[chief-inspector]

The 2023 NEC and the 2021 IBC have very similar definitions of "Structure":

2021 IBC "STRUCTURE. That which is built or constructed."
2023 NEC "Structure. That which is built or constructed, other than equipment."

The NEC added that last clause "other than equipment" in the 2017 version to clarify, for example, that if you run a feeder to a free-standing self-contained power pedestal set in the middle of a field, it is equipment only, therefore not a structure, and therefore does not require a grounding electrode system. [If you instead use a panelboard on a 4x4 post in the ground, it is still a bit ambiguous whether the 4x4 post is equipment or not; if not, that is a structure and would require a grounding electrode system.]

However, the 2023 NEC and 2021 IBC have very different definitions of "Building":

2021 IBC "BUILDING. Any structure utilized or intended for supporting or sheltering any occupancy."
2023 NEC "Building. A structure that stands alone or that is separated from adjoining structures by fire walls."

[Apparently the NEC is happy to call a flagpole or a human-scale sculpture a building, but the IBC does not wish to do that.] The main distinction the NEC is making between structures and buildings is that bit about firewalls. For the NEC a series of townhouses separated by firewalls would be one structure but multiple buildings; and so for example when 230.2 says in effect "one service per building," that automatically allows one service per townhouse without requiring any exception or other language.

My question is a basic one about the IBC, with which I'm not so familiar, particularly its fire requirements. What is the IBC equivalent term for the way the NEC is using the term "Building"? I.e. a portion of a structure which is separated by (sufficiently rated) firewalls?

Thanks,
Wayne

The code was written by committees that argued about what should be in it and many times is a mess. A firewall used to always be any type of fire demising wall but now I believe it's a 4-Hour wall.