Exterior Wall Rating less than 10'-0"

Per IBC section 705.5 when two buildings have a separation distance greater than 10’-0" the rating of exterior walls shall comply with both requirements in tables 601 and 602 whichever is stricter, because the danger is assumed to come from the inside. When the buildings are less than 10’-0" the danger is assumed to be from the exterior due to the possibility of self-ignition. The wall must then be rated for both interior and exterior.

My question is how do we determine the rating of an exterior wall with an existing adjacent building less than 10’-0" with a different construction type? Do I use table 706.4 regardless of construction types?

Jeffrey Doering August 25, 2020 18:15

Carefully read the definition of Fire Separation Distance (FSD) in IBC Chapter 2. It’s not the distance between two buildings… in the case of your example, it would be to an imaginary line between the two buildings (assuming they reside on the same lot). So, Say building A and B are 10ft apart on the same property. So, you’d draw that ‘imaginary line’ and take the FSD for each building to that line. Both buildings could be 5ft. One could be 0’ and the other 10’. But, wherever you draw that line, you need to make sure both buildings are compliant.

Exterior Wall Rating less than 10'-0"

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