2 hour fire walls terminating at roof deck

[milam@tomanbrothers.]

Plans calling for 1 hour protection of roof deck, 4' out per 706.6. Does all the structure need to be protected 4' out ? ie; BEAMS AND BARJOISTS ? primaries column to column ? or just 4' out ???
Milam

 

[RLGA]

Which exception to Section 706.6 are they using: 2, 3, or 4?

 

[walker.t]

Does all the structure need to be protected 4' out ?

The structure supporting the portion of the roof 4’ out must be protected for its entire length:

2018 IBC 706.6 Exception 2:
2. Two-hour fire-resistance-rated walls shall be permitted to terminate at the underside of the roof sheathing, deck or slab, provided that:
2.1 The lower roof assembly within 4 feet of the wall has not less than a 1-hour fire-resistance rating and the entire length and span of supporting elements for the rated roof assembly has a fire-resistance rating of not less than 1 hour. [emphasis added]

That includes beams and bar joists, as well as the vertical elements supporting the beams and bar joists (such as columns and load-bearing walls.)