706.6.1 Stepped buildings?

[mtlogcabin]

2009 IBC

Downtown existing buildings. Lower single story building is CMU. Adjacent 2 story building is a V-A. DP is wanting to use the stepped building section to install 3/4 protected fixed glazing along the upper level. There is a property line running between the 2 buildings with about a 5 inch air space between them.

Question 1 Is section 706.6.1 applicable on a property line?

Question 2 If no would the fixed glazing be permitted if it was 1.5 hour rated per Table 715.5?

 

[RLGA]

Question 1: No. Per Section 706.1.1, party walls are those that separate buildings with an actual lot line between the buildings. However, since the wall is not shared, it technically is not a fire wall, thus, not a party wall, either. Buildings on separate properties must comply with the fire-separation distances and opening protection requirements of Table 705.8, since a physical lot line exists. Therefore, Section 706.6.1 could not be considered--its intent was for buildings on the same lot with differing heights at the fire wall location.

Question 2: Openings are not pemitted at that fire separation distance. However, glazed windows having a fire-resistance rating per ASTM E 119 equal to or greater than the adjacent wall should be permitted, since such an assembly is not considered an opening. However, what's there to prevent the owner on the adjacent lot from building a higher building that could block any view?

 

[peach]

I'm having this exact same discussion for a new "infill" hotel.

 

[mtlogcabin]

However, what's there to prevent the owner on the adjacent lot from building a higher building that could block any view?

Nothing at this time. There was discussion about purchasing a "No Build Easement" from the single story building owners that limit the height of all buildings on that property. Future expansion blocking a view isn't a code issue as long as the glazing is rated the same as the wall or higher. In this case 90 minutes is required to be compliant.