Projection Conjection - 2012

[AegisFPE]

The attached a 1997 UBC Handbook image illustrating how an opening in an exterior wall perpendicular to a lot line can occur adjacent to the lot line. A similar conclusion could be drawn from previous IBC Commentary Editions illustrating that the fire separation distance is measured perpendicular to the exterior building wall, not perpendicular to the lot line (Figure 702.1(6)).But, in the 2012 IBC Commentary, we do not find an exhibit that shows how a fire separation distance is measured between a wall and lot line where the wall and lot line are not parallel. In addition, the 2012 IBC has revised the provisions for projections in proximity to a lot line. As such, there may be room for interpretation on whether the fire separation distance is measured perpendicular from the building wall or perpendicular from the lot line.That said, under the IBC (and does your answer change between the 2009 to the 2012?) for building built up to a lot line on one side:1. Is it acceptable to have an unprotected opening zero feet from the lot line in a wall perpendicular to the lot line as shown in the UBC Handbook Figure?2. Can a projection extending from that perpendicular wall exist for the entire length of the wall, or must it be maintained some distance away from the lot line?

View attachment 1733

View attachment 1733

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[Builder Bob]

That depends would be the best answer I could give - A party wall (firewall) requires opening protective for four feet ........ However, as a general rule of thumb, I would say your diagram is accurate still. (Personally, I do not like this concept as the windows are potential exposure points for fire spread........

 

[cda]

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