Eaves in building area calculation?

[wwhitney]

Even if the Chapter 2 definition of “building area” doesn’t mention the number of floors, the use in 506 supports the interpretation that it means “total area of all stories in a building” which is what you would call “floor area.”

Well, from my point of view, the usage in 506 can't change the definition. And the definition indicates "building area" does not count multiple floors, so the usage in 506 is just sloppy. 506 appears to incorrectly conflate building area and floor area. I briefly skimmed the uses of the actual phrase "building area" in 506 and I don't think any of them are critical, in that all the actual enforceable requirements can be traced to a different term.

Of course, that raises the question if any section of the IBC is using "building area" according to the definition. If not, might as well change the definition if that's more convenient than changing Chapter 5.

But in the IBC, “building area” is to the inside face of the walls

I don't think I agree. In the definition of "floor area, gross" we have the language "The floor area within the inside perimeter of the exterior walls . . ." which explicitly excludes the "footprint" of the walls themselves. Whereas "area, building" says "the area included within surrounding exterior walls . . ." So in contrast to "floor area, gross," by not explicitly referencing the "inside perimeter", I read the "area, building" as including the footprint of the exterior walls. Which makes sense, as it includes the footprint of the eaves as well (the OP in this thread).

No, they are the same in that regard, neither “building area” nor “gross floor area” include the exterior walls based on the commentaries.

OK, but as an outsider I reject the idea that a commentary can overrule the plain meaning of the definitions themselves. The internal contrast between the wording of "area, building" and "floor area, gross" carries greater weight, in my opinion, than any external commentary.

The commentary is useful, though, to understand the intention, and so if the commentary and the usage conflict with the language of the definition, then the easiest fix is to change the definition.

Your comments about "building area" appearing primarily (exclusively?) in 506, and "gross floor area" appearing primarily (exclusively?) in 1004 make me wonder whether those two sections of the IBC come from different progenitor codes, that each had different definitions, and whether those sets of definitions were just merged without any attempt to reconcile them with each other into a coherent whole. Because it certainly doesn't seem coherent to me.

Cheers, Wayne

 

[Yankee Chronicler]

I haven't studied Chapter 10, but if it is using the term "floor area" without any further modifiers, then I conclude it is referring to the definitions in Chapter 2, and the "floor area, gross" definition excludes the region of a balcony outside the exterior walls that is open to the sky directly above (straight up). So then I would say no, as written.

Again, if this is not the intention, then the definitions are sloppy, which is disappointing.

Edit: is there no language in Chapter 10 to deal with occupant loads attributable to spaces open to the sky above, like decks or rooftop parking in parking garages?

Cheers, Wayne

You are correct, but by that logic there is no language in the code to deal with occupant load of interior (surrounded on all four sides) courtyards, yet when they occur we have to provide egress from them.

 

[wwhitney]

You are correct, but by that logic there is no language in the code to deal with occupant load of interior (surrounded on all four sides) courtyards

As per earlier in the thread, doesn't 1004.7 cover this?

Cheers, Wayne

 

[walker.t]

the usage in 506 can't change the definition

I would agree that the use of a defined term should coordinate with the given definition of that term, but 506 is definitely referring to total area of all stories of a building. I would say in this case that the usage in 506 serves to clarify what the definition should say.

I don't think I agree. In the definition of "floor area, gross" we have the language "The floor area within the inside perimeter of the exterior walls . . ." which explicitly excludes the "footprint" of the walls themselves. Whereas "area, building" says "the area included within surrounding exterior walls . . ." So in contrast to "floor area, gross," by not explicitly referencing the "inside perimeter", I read the "area, building" as including the footprint of the exterior walls. Which makes sense, as it includes the footprint of the eaves as well (the OP in this thread).

My understanding is that the generally accepted interpretation of “the area within surrounding exterior walls” in the definition of “building area” is that it means to the interior perimeter. It would be nice if the definition of “building area” did include “inside perimeter” but it doesn’t.

if the commentary and the usage conflict with the language of the definition, then the easiest fix is to change the definition.

For sure, that would be great. Hold your breath and count how many shades of blue you turn while you wait for that to happen!

You might consider investigating how you can get on one of the committees that works on revisions to the code, or maybe there’s a way to submit suggestions for corrections/refinements to the code.