Vertical exposure

[Sifu]

2018 IBC 708.5.6, Vertical exposure. This section applies to buildings on the same lot. Commentary explains it well but does not address the limitation that they are on the same lot. What if I have a building within 15' horizontally and within 15' vertically of the openings above it on the lot next door? Seems like the theory for protecting the building is sound, why wouldn't it include the building next door?

 

[ChrisCampbell]

708.5.6 requires you to measure the horizontal distance between your building and an imaginary lot line drawn between your building and the adjacent building. If the adjacent building was on a separate lot, it would also have required opening protectives based on Table 705.8, but those are based on the fire separation distance to the actual lot line, not an imaginary one. With only 15' between buildings, both buildings would have some level of limitation on openings per the Table.

Note that if the buildings are on the same lot, Exception 1 to 705.8.6 would allow you to completely eliminate the opening protectives on the wall above the adjacent roof, as long as that adjacent roof is rated. If the buildings are on different lots, the requirements of Table 705.8 would apply, regardless of the rating of the roof.

 

[Sifu]

Looks like I gave the wrong code section. Should be 705.8.6, but the question remains. It appears to only address buildings on the same lot. I have an existing building within 1 foot of the lot line. A new building is proposed 9 feet from the same lot lone on the other side. They are on different lots, and the existing building is not constructed with a fire resistant roof...or walls for that matter. So logic dictates if buildings on the same lot need protection, then so would buildings across the line from each other. If using 705.8.6 then every opening requires protection if within 15' vertically. If using t705.8 then not every one would. So I guess I don't understand why buildings on the same lot require a higher degree of protection than buildings at the same distance, spanning a lot line. To add oil to the water, it is a podium, and some of it is S-2 open parking, with R2 above. I don't yet know exactly what the elevations are, but it looks like the garage AND possibly the lower levels of the R2 will be within 15' vertical and 15' horizontal.