Line location between buildings on the same lot

IBC 2015. We are looking at constructing two buildings on a single lot. Can the imaginary line between them (per 705.3) be located at unequal distances from each building? I.e. 5' from one building and 15' from the other?

My goal for this specific instance is to not have to build parapets on the walls facing the dividing line. One building will be sprinklered F-1 occupancy; the other will be non-sprinklered U occupancy. The line will be set to allow for 25% unprotected openings.

classicT

MODERATOR
Joined Aug 2, 2017 Messages 3,267 Location AZ, USA FIRE SEPARATION DISTANCE. The distance measured from the building face to one of the following:

1. The closest interior lot line.
2. To the centerline of a street, an alley or public way.
3. To an imaginary line between two buildings on the lot. The distance shall be measured at right angles from the face of the wall.
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Per the above definition (#3), the imaginary line does not have to be centered. Thereby, if you can follow Table 602 for each building, you should be alright. I'd show the imaginary "property" line on the Civil Site Plan and note setback distance with required fire-resistance rating required per the construction type.

fatboy

Administrator
Joined Oct 17, 2009 Messages 6,864 Location Northern CO

I agree with Ty J.

Be no different than a real property line, if both building have what they need for separation, you are golden.

RLGA

SAWHORSE
Joined Oct 18, 2009 Messages 3,400 Location Phoenix, AZ

IBC 2015. We are looking at constructing two buildings on a single lot. Can the imaginary line between them (per 705.3) be located at unequal distances from each building? I.e. 5' from one building and 15' from the other?

My goal for this specific instance is to not have to build parapets on the walls facing the dividing line. One building will be sprinklered F-1 occupancy; the other will be non-sprinklered U occupancy. The line will be set to allow for 25% unprotected openings.

Short answer: yes. However, the construction of the walls will be different between the two based on the different fire separation distances (FSD). The one with a 5-foot FSD will likely need at least a 1-hour rating designed for exposure from inside and outside, while the other wall with a 15-foot FSD may have either a 1-hour rating or no rating depending on the type of construction. If a 1-hour rating is required, then it may be designed for an inside exposure only.