Chapter 5 Builidng Area

[Mech]

2009 IBC

When calculating the building area, I assume we should be using the exterior perimeter of the exterior wall?

Thanks,

 

[mtlogcabin]

AREA, BUILDING. The area included within surrounding exterior walls (or exterior walls and fire walls) exclusive of vent shafts and courts. Areas of the building not provided with surrounding walls shall be included in the building area if such areas are included within the horizontal projection of the roof or floor above.

 

[texasbo]

If I'm not mistaken, the UBC specified how to calculate. But it's a good question; I couldn't find if the thickness of the walls are calculated or not in the IBC. I think we go from outside face, but I'm not sure that's mandatory.

 

[mark handler]

AREA, BUILDING The area included within surrounding exterior walls (or exterior walls and firewalls) exclusive of vent shafts and courts. Areas of the building not provided with surrounding walls shall be included in the building area if such areas are included within the horizontal projection of the roof or floor above.

 

[Frank]

"Within the exterior walls"

Within starts on the interior face of the wall--wall thickness is excluded.

 

[alora]

"Within the exterior walls"Within starts on the interior face of the wall--wall thickness is excluded.

Yep.

Also having the commentary helps quite a bit.

 

[jpranch]

This is from the 2006 IBC Handbook Fire & Life Safety Provisions:

Section 502 Definitions

AREA, BUILDING. The term building area describes that portion of the building’s floor

area to be utilized in the determination of whether or not a structure complies with the

provisions of Chapter 5 for allowable building size. It is not to be confused with the term

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floor area, which is the basis for occupant-load determination in Chapter 10 for means of

egress evaluation, nor the term fire area as addressed in Chapter 7.

The definition of building area is the area included within the surrounding exterior walls

of the building, and the definition further states that the floor area of a building or portion

thereof not provided with surrounding exterior walls shall be the usable area under the

horizontal projection of the roof or floor above. The intent of this latter provision is to

address where a building may not have exterior walls or may have one or more sides open

without an enclosing exterior wall. Examples would include a canopy covering pump

islands at a service station, or the drive-through area of a fast food restaurant. Where a

column line establishes the outer perimeter of the usable space under the roof, it is also

typically the extent of building area. Beyond the column line, the overhead cover is simply

viewed as a projection. See Figure 502-1. If all of the area beneath the roof above can be

considered usable space, then the building area is measured to the leading edge of the roof

above. See Figure 502-2.

​

84 2006 IBC Handbook