Draftstopping in Combustible Construction / Attics (IBC 2021)

[ZKARCH]

I would like to validate my interpretation of the Draftstopping requirements as they apply to this portion of the stated project and appreciate any effort towards this end.
Project Info: I-1 Condition 1 Occupancy, Type VB Construction, One Story w/ Ventilated Attic
Please refer to the image attached/below:
Red lines - Draftstopping required by 708.4.2; Item 2 (Corridor and Sleeping Unit Separation Fire Partitions)
Blue lines - Draftstopping omitted per by 708.4.2; Exception 2 (Corridor Fire Partions)
(Where corridor walls provide a sleeping unit or dwelling unit separation, draftstopping shall only be required above one of the corridor walls)
Orange Line - Draftstopping required by 718.4 to separate the remaining area into areas that do not exceed 3,000sf



The focuses of the thread are as follows in order of importance:
(A) General Validation of Draftstopping Provisions
(B) Validation of Omission of Blue Line Draftstopping per 708.4.2; Exception 2
(C) This building is Sprinklered in accordance with Section 903.3.1.1 which should serve as an exception to all the draftstopping provided above required by 708.4.2 and 718.4. In a previous project under the same conditions a dry system was installed in the attic space. This post is attempt to provide the means for draftstopping the attic to avoid installing the attic dry system - though as I understand it, providing draftstopping in the attic in itself does not exempt the concealed, combustible, attic space from being sprinklered per NFPA 13. Any elaboration on NFPA 13 requirements and avoiding sprinklers in the attic space would also be appreciated as this is the path I was asked to go down but don't completely understand why.

 

[Construction Daily]

Good breakdown. The omission of the blue line per 708.4.2 Exception 2 makes sense here since you already have corridor separation above one wall. Curious—have you had an AHJ confirm that in past projects?

 

[ZKARCH]

Whereas in an alternate I-1 configuration, the following approach seems more logical for the sake of creating draft stopped compartments between sleeping units while not providing redundancy at each corridor wall. Curious what others think in comparison to the original example (where the whole north set of units are not compartmentalized from each other).

Red lines - Draft stopping required by 708.4.2; Item 2 (Corridor and Sleeping Unit Separation Fire Partitions)
Blue lines - Draft stopping omitted per by 708.4.2; Exception 2 (Corridor Fire Partitions)
(Where corridor walls provide a sleeping unit or dwelling unit separation, draft stopping shall only be required above one of the corridor walls)
Green Lines - Draft stopping provided to compartmentalize adjacent sleeping units where corridor draft stopping is omitted per 708.4.2; Exception 2 (Blue Lines)

 

[steveray]

Never seen anyone want to do the green lines, easier to do the blue...

 

[Paul Sweet]

The green lines would make draft stopping easier to install if the roof has trusses perpendicular to the corridor.