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Is basement area considered part of the fire area

M

Morphdesigns

Sawhorse
Joined
Dec 4, 2013
Messages
44
Location
Waupun
I have a VB, S-1 occupancy maintenance building. The building itself is 11,400 sqft. I also have an open mezzanine, that will be 550 sqft. And finally, I have a basement level, that is fully exposed on 1 end, and fully underground on the other 3 sides. This is not considered a story based on the Grade Plane Determination Worksheet". The floor area of the basement is 1600 sqft.

Table 506.2, has allowable area of 9000 sqft. In adding frontage increase, per 506.3, I have a new allowable area of 15,570 sqft.
We do not want to sprinkler the building, so we are considering the fire area to be under 12,000 sqft per 903.2.9.

Per IBC 505.2, it states the mezzanine area shall be included in the fire area, so that puts the building above grade, at 11,950 sqft. I have not found anything in the code that states the basement area need to be included in the fire area. I have only found section 506.1.3, that states basements need not to be included in the total allowable floor area of a building.

I have a national post frame builder that is telling me that we need to rate the floor system above the basement, and provide a 3-hr horizontal assembly system per table 707.3.10 to separate the basement and main level, because otherwise the 1600 sqft basement needs to be include in the fire area of the whole project. And we need to do that, because we do not want to sprinkler the building, and adding in the 1600 sqft, puts it over the 12,000 area per ibc 903.2.9

I know is a holiday weekend, but hopefully some people are die-hard works and still working and able to give some insight.

Thanks all. Happy 4th.
 
Your basement is a floor area by definition and use so it is included in the Fire Area calculation.
Can you create a separate 1600 sq foot fire area on the 1st floor? A 3-hour wall is a whole lot easier to construct than a floor assembly.

[BF] FIRE AREA. The aggregate floor area enclosed and bounded by fire walls, fire barriers, exterior walls or horizontal assemblies of a building. Areas of the building not provided with surrounding walls shall be included in the fire area if such areas are included within the horizontal projection of the roof or floor next above.

[BG] STORY. That portion of a building included between the upper surface of a floor and the upper surface of the floor or roof next above (see “Basement,” “Building height,” “Grade plane” and “Mezzanine”). A story is measured as the vertical distance from top to top of two successive tiers of beams or finished floor surfaces and, for the topmost story, from the top of the floor finish to the top of the ceiling joists or, where there is not a ceiling, to the top of the roof rafters.

[BE] FLOOR AREA, GROSS. The floor area within the inside perimeter of the exterior walls of the building under consideration, exclusive of vent shafts and courts, without deduction for corridors, stairways, ramps, closets, the thickness of interior walls, columns or other features. 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 gross floor area shall not include shafts with no openings or interior courts.
 
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