Unprotected Openings from Adjacent Buildings

[Francis Vineyard]

Reference 2012 IBC; I believe the 2015 & 2018 are identical.

Does the exception to 705.8.6 require both of these roofs to be 1-hr. assemblies for 10 ft.?

Example; there are two (2) buildings on the same side of imaginary line across from the taller building. Building “A” is at the imaginary and building “B” is 14.5 ft. away.

Seems odd by comparison in accordance with exception to 706.6.1 for Fire Walls the same condition is only for 10 ft. (plus no roof openings) from the taller building exterior wall to allow for unprotected openings.

705.8.6 Vertical exposure. For buildings on the same lot, opening protectives having a fire protection rating of not less than 3/4 hour shall be provided in every opening that is less than 15 ft. vertically above the roof of an adjacent building or structure based on assuming an imaginary line between them. The opening protectives are required where the fire separation distance between the imaginary line and the adjacent building or structure is less than 15 ft.

Exceptions:

1. Opening protectives are not required where the roof assembly of the adjacent building or structure has a fire-resistance rating of not less than 1 hour for a minimum distance of 10 feet from the exterior wall facing the imaginary line and the entire length and span of the supporting elements for the fire-resistance-rated roof assembly has a fire-resistance rating of not less than 1 hour.

 

[RLGA]

"Does the exception to 705.8.6"...what? I think you left out a critical part of your post. I'm not sure exactly what is in question.

 

[Francis Vineyard]

Reference 2012 IBC; I believe the 2015 & 2018 are identical.

Does the exception to 705.8.6 Example; two (2) buildings on the same side of imaginary line across from the taller building. Building “A” is at the imaginary and building “B” is 14.5 ft. away; is it required from both of these roofs to be 1-hr. assemblies for 10 ft.?

"Does the exception to 705.8.6"...what? I think you left out a critical part of your post. I'm not sure exactly what is in question.

Ron, thank you! I change my question in the OP. Hope this makes sense.

 

[RLGA]

Yes, Exception 1 to Section 705.8.6 would require both roofs to be of 1-hour construction. The Exception eliminates the opening protective requirement for the tall building, but does not override the fire separation distance requirement for the lower buildings; thus, if an adjacent lower building is within 15 feet of the imaginary lot line, then a 1-hour roof is required per the Exception.

I know it doesn't make sense--this could be a candidate for a revision in the 2021 edition.