Hello. Newbie member here. Doing a review and need help to figure out what/ how/what to apply for this building.
Mixed Occupancy, New construction Type VB- 2 stories. B occupancy at main level with R-3 above. No fire-sprinkler system (Local code amended IBC requirement for R occupancy that automatic sprinkler system will be required only if the R building meets certain criteria. In this case, the R occupancy is not required to have an automatic sprinkler system.)
The mixed occupancy method of choice is Non-Separated Occupancy. Overall Square Footage and height is below most restrictive for a VB type, B occupancy - Per Table 508.2 Max SF is 9000 and Height is 40'. The building overall area for both occupancies is a total of 7700 SF - 27'6" Overall height. The B is 6600 SF and the R3 is 1100 SF.
Section 420, in my mind, makes it that there is always a required separation when there is an R occupancy involved. In this case, Section 420.3 applies.
Section 420.3 Horizontal Separation. Floor assemblies separating dwelling units in the same buildings, floor assemblies separating sleeping units in the same building and floor assemblies separating dwelling or sleeping units from other occupancies contiguous to them in the same building shall be constructed as horizontal assemblies in accordance with section 711.
Applying Section 711 is where my concern lies.
Section 711.2.3 Supporting construction. The supporting construction shall be protected to afford the required fire-resistance rating of the horizontal assembly supported.
Exception: In buildings of Type IIB, IIB or VB construction, the construction supporting the horizontal assembly is not required to be fire-resistance at the following: (There are 3, I will only state1 that is applicable)
2. Horizontal assemblies at the separations of dwelling units and sleeping units as required by Section 420.3
Section 711.2.4.1 Separating mixed occupancies. Where the horizontal assembly separates mixed occupancies, the assembly shall have a fire-resistance of not less than that required by section 508.4 based on the occupancies being separated.
Section 711.2.4.3. Dwelling and sleeping units. Horizontal assemblies serving as dwelling or sleeping unit separations in accordance with Section 420.3 shall not be less than 1-hour fire-resistance-rated construction.
I am leaning towards the interpretation that since 420.3 is distinctly identified in Section 711.2.3 and 711.2.4.3 that the fire-resistance rating only needs to be a 1-hour rated assembly and the supporting construction need not be rated. But the discussion arises that Section 711.2.4.1 should be the applicable section to this building because we are separating two different occupancies. This then pushes the fire-resistance rating to be a 2-hour rated assembly based on table 508.4 between an R and B. Non sprinklered, including the supporting construction.
So my question (and get a consensus) is what would be the correct application and rating for the separation?
Mixed Occupancy, New construction Type VB- 2 stories. B occupancy at main level with R-3 above. No fire-sprinkler system (Local code amended IBC requirement for R occupancy that automatic sprinkler system will be required only if the R building meets certain criteria. In this case, the R occupancy is not required to have an automatic sprinkler system.)
The mixed occupancy method of choice is Non-Separated Occupancy. Overall Square Footage and height is below most restrictive for a VB type, B occupancy - Per Table 508.2 Max SF is 9000 and Height is 40'. The building overall area for both occupancies is a total of 7700 SF - 27'6" Overall height. The B is 6600 SF and the R3 is 1100 SF.
Section 420, in my mind, makes it that there is always a required separation when there is an R occupancy involved. In this case, Section 420.3 applies.
Section 420.3 Horizontal Separation. Floor assemblies separating dwelling units in the same buildings, floor assemblies separating sleeping units in the same building and floor assemblies separating dwelling or sleeping units from other occupancies contiguous to them in the same building shall be constructed as horizontal assemblies in accordance with section 711.
Applying Section 711 is where my concern lies.
Section 711.2.3 Supporting construction. The supporting construction shall be protected to afford the required fire-resistance rating of the horizontal assembly supported.
Exception: In buildings of Type IIB, IIB or VB construction, the construction supporting the horizontal assembly is not required to be fire-resistance at the following: (There are 3, I will only state1 that is applicable)
2. Horizontal assemblies at the separations of dwelling units and sleeping units as required by Section 420.3
Section 711.2.4.1 Separating mixed occupancies. Where the horizontal assembly separates mixed occupancies, the assembly shall have a fire-resistance of not less than that required by section 508.4 based on the occupancies being separated.
Section 711.2.4.3. Dwelling and sleeping units. Horizontal assemblies serving as dwelling or sleeping unit separations in accordance with Section 420.3 shall not be less than 1-hour fire-resistance-rated construction.
I am leaning towards the interpretation that since 420.3 is distinctly identified in Section 711.2.3 and 711.2.4.3 that the fire-resistance rating only needs to be a 1-hour rated assembly and the supporting construction need not be rated. But the discussion arises that Section 711.2.4.1 should be the applicable section to this building because we are separating two different occupancies. This then pushes the fire-resistance rating to be a 2-hour rated assembly based on table 508.4 between an R and B. Non sprinklered, including the supporting construction.
So my question (and get a consensus) is what would be the correct application and rating for the separation?
