Calculating opening protection on modulated walls

[Yikes]

- Two multistory buildings on the same site have an imaginary property line between them
- Table 705.8 allows various percentages of openings based on distance to PL
- Walls of the two buildings vary in distance (including the balcony gurad wall, as AHJ considers oute edge of balcony to be an "opening";

How do you calculate percentage of openings when the facade modulates in depth? Do you take each modulated segment into account separately?

 

[RLGA]

Which code edition is adopted?

 

[Builder Bob]

In a bad sense , yes the further away from the property line the greater the % of openings required.... otherwise, the AHJ may use the most restrictive and apply it to the entire wall facing the property line -

 

[Yikes]

Which code edition is adopted?

2016 CBC / 2015 IBC

 

[Yikes]

Also, do you agree with the plan checker's assertion that the face of a projecting exterior balcony is a "wall opening"?

 

[Builder Bob]

Not necessarily as an opening - however, you do need to meet the requirements of chapter 14 and I believe that FSD is referenced by that as well for what construction type /materials/protection that are allowed.

 

[RLGA]

Also, do you agree with the plan checker's assertion that the face of a projecting exterior balcony is a "wall opening"?

The definition of an exterior wall states it's an "enclosing wall," which is not very definitive; however, Section 705.2 may help you.

Section 705.2 addresses projections, which it describes as "Cornices, eave overhangs, exterior balconies, and similar projections extending beyond the exterior wall..." Thus, I would say those are projections and not exterior walls with unprotected openings.

The reason I asked about which edition is that the 2018 IBC has clarified the application of fire separation distance for multi-story buildings in Section 705.8.1. I'm not sure if the floor plate of each story is the same for every story, but if they vary, the fire separation distance is measured per story. So if the second story projects over the first story, then each story will have its own applicable fire separation distance.

As for walls with varying fire separation distances (FSD), for each wall segment with a different FSD, you would use the wall area of that segment only in determining the percentage of openings.