# Measuring Fire Area



## classicT (Nov 17, 2020)

Given the definition as follows:

*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.

When calculating fire area for a building with non-fire-resistance rated exterior walls, is the fire area measured from the exterior face-of-wall, or to the interior face-of-wall?

Where exterior walls are of fire-resistance rated construction, is it appropriate to measure to the interior face-of-wall?


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## RLGA (Nov 17, 2020)

Inside the walls, whether fire-resistance-rated or not.


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## classicT (Nov 17, 2020)

RLGA said:


> Inside the walls, whether fire-resistance-rated or not.


Anywhere definitive that you pull this from?

Issue I have, is if  you have a building with no walls, you measure to the exterior edge of the roof. Per the definition, you include any projections of the roof.


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## cda (Nov 17, 2020)

classicT said:


> Anywhere definitive that you pull this from?
> 
> Issue I have, is if  you have a building with no walls, you measure to the exterior edge of the roof. Per the definition, you include any projections of the roof.



I got my hand spanked on fire area.

Maybe needs a code redo on the definition.

I would say to inside of walls, when present.

Maybe measure the slab, when no walls??


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## RLGA (Nov 17, 2020)

classicT said:


> Anywhere definitive that you pull this from?
> 
> Issue I have, is if  you have a building with no walls, you measure to the exterior edge of the roof. Per the definition, you include any projections of the roof.


The definition uses the phrase "area enclosed and bounded by," which means the area within those elements.


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## mtlogcabin (Nov 18, 2020)

classicT said:


> Issue I have, is if you have a building with no walls, you measure to the exterior edge of the roof


That is the intent of the code in all the definitions of area except net area. You measure to the interior face of the exterior walls and if no walls then you measure to the horizontal projection of the roof or floor above

[BG] 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.*

[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.

[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.*


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## steveray (Nov 18, 2020)

I'm with MT on explanation (and Ron)....Walls, inside; no walls, edge of roof


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## my250r11 (Nov 18, 2020)

The use of floor area/area enclosed and how it is used in all the definitions except for when talking about projection is what makes me believe it is to the inside


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## Blazer (Nov 18, 2020)

If the area is not covered with a roof that "projects" from area that does contain walls then we do not consider it as part of the building area. It is just a canopy with individual supports and is not attached to portion of other building. It just provides shade and open to exterior all around it. A building typically is for sheltering from weather and regulating temperatures. As long as occupants are not above the area not containing walls and roof is not attached to enclosure then it really shouldn't be considered in the building area or fire area because it doesn't pose a risk to life safety.


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## cda (Nov 18, 2020)

Blazer said:


> If the area is not covered with a roof that "projects" from area that does contain walls then we do not consider it as part of the building area. It is just a canopy with individual supports and is not attached to portion of other building. It just provides shade and open to exterior all around it. A building typically is for sheltering from weather and regulating temperatures. As long as occupants are not above the area not containing walls and roof is not attached to enclosure then it really shouldn't be considered in the building area or fire area because it doesn't pose a risk to life safety.





My example, that I got my hand slapped on:::


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## classicT (Nov 18, 2020)

cda said:


> My example, that I got my hand slapped on:::
> 
> 
> 
> ...


This is kind of my point though.... For the photo example, where do you measure to? 

Is it the entire area under the projection of the roof? If so, then your including the area of the "walls".

If you measure to the inside face of wall, what happens if it is not a solid wall as pictured? Or walls on (3) sides that get measured to interior face, but where a wall is not provided, you must measure to the outward projection of the roof? Think about it... why would you increase the fire area (penalty possible) for removing a wall?


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## cda (Nov 18, 2020)

classicT said:


> This is kind of my point though.... For the photo example, where do you measure to?
> 
> Is it the entire area under the projection of the roof? If so, then your including the area of the "walls".
> 
> If you measure to the inside face of wall, what happens if it is not a solid wall as pictured? Or walls on (3) sides that get measured to interior face, but where a wall is not provided, you must measure to the outward projection of the roof? Think about it... why would you increase the fire area (penalty possible) for removing a wall?




My other hand slap example, but no overhang on the front end:::


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## RLGA (Nov 18, 2020)

classicT said:


> This is kind of my point though.... For the photo example, where do you measure to?
> 
> Is it the entire area under the projection of the roof? If so, then your including the area of the "walls".
> 
> If you measure to the inside face of wall, what happens if it is not a solid wall as pictured? Or walls on (3) sides that get measured to interior face, but where a wall is not provided, you must measure to the outward projection of the roof? Think about it... why would you increase the fire area (penalty possible) for removing a wall?


An _exterior wall_ and an _exterior wall envelope_ are not necessarily one and the same. 

Is the enclosure around the boat storage an _exterior wall_? Yes, by IBC definition, since it is an enclosing wall that is bearing or nonbearing (looks to be nonbearing since the columns are supporting it) and is more than 60-degrees from the horizontal. There is no mention of protecting the interior from the exterior.

Next, are those walls an _exterior wall envelope_? By IBC definition, no, since they are not protecting the structural members, conditioned interior space, etc. from the effects of the exterior environment.

Since the definition of a fire area uses _exterior wall_ and not _exterior wall envelope_, then the measurement is to the inside of what constitutes an exterior wall even though it is as porous as a sieve.


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## Builder Bob (Dec 15, 2020)

CDA High Piled Storage for boats eh?


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## cda (Dec 15, 2020)

Builder Bob said:


> CDA High Piled Storage for boats eh?




possible, possible


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