Frontage increase in H shaped building

[emcc845]

I'm currently working on an addition to an existing building. I'm trying to determine allowable area (IBC 24) and how much frontage increase is available. The existing building is H shaped. I'm wondering if the area shown in blue below/attached:

A. would be counted in the building perimeter​

B. Be considered to have no open space since it's only 18' between the two portions of the building.​

The above is my understanding of the code. I've had a colleague disagree.

I appreciate any input you would offer!

 

[Sifu]

I don't think blue can be open space at 18', but it is perimeter. I think the rest would be open space if it is all 20' or greater. As I have discovered recently, even if the blue were 20', it may be advantageous to pull it out of the open space since the entire width of open space would then be limited to 20' and reduce the value in the table entry.

 

[walker.t]

I don't think blue can be open space at 18', but it is perimeter.

I agree, except you can say “know” instead of “think” on that 18’ dimension.

I've had a colleague disagree.

2021 IBC 506.3.2 clearly states that the pubic way or open space must have a minimum width of 20’.