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Perimeter access

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DwightB

Guest
The more I read codes, the more I begin to question my assumptions. I've always assumed that if there is a fire wall, then there is a portion of the building that does not have the required perimeter access. For instance, assuming a square building, with code compliant clear distance all the way around, so that F=P, I can have (1-.25) x allowable area. But suppose the building is twice as wide, with a firewall down the middle. I've always assumed my accessible perimeter is now only 75% (3 of the 4 sides) and the increase is now (.75-.25) x allowable area.

Is that correct?
 
That is correct. Each building is treated separately for height and area, and the side with the fire wall does not offer the open frontage that the increase permits.
 
It almost seems like it would be more logical to subtract that fire wall from total perimeter and then re-figure accessible frontage. The firewall removes that frontage from exposure to risk.
 
Dwight

What do you do when the building is designed as a single structure and the fire wall is there only to separate fire areas of two different occupancy classifications and the areas of both sides meet the area limits of Table 503?
 
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