Appeal 34840

2022 OSSC TABLE 601 FIRE-RESISTANCE RATING REQUIREMENTS FOR BUILDING ELEMENTS (HOURS)

Building elements are required to have a fire-resistance rating per Table 601. For Type IA construction, the following fire-resistance ratings are required:
3-hour Primary structural frame
2-hour Floor construction and associated secondary structural members

Allow omission of rated construction of second level within dwelling units provided fire sprinkler design is based on Ordinary Hazard Group 2 (OH2) occupancy.

The Mississippi at Cook residential mixed-use project is an existing podium-style building with four (4) stories of Type VA construction above a single story of Type IA. Occupancies include Groups A-3, B, and predominantly R-2.
Alterations are proposed to turn the existing ground-level (originally permitted as commercial space) at the SW corner into four (4) dwelling units. Three (3) of the units will have a second level that is atmospherically open to that unit below.
Plan view and section views of the units are attached.
Materials used in the second level floor/ceiling assembly will comply with requirements for Type IA construction utilizing a 2-hour rated UL H505 design. Framing will support the second level only with no floor / ceiling loads or connections to podium floor above. Existing sprinkler design was based on restaurant/mercantile (OH Group2 occupancy), and is provided throughout each unit, including below the second level. The four dwelling units will be separated by 1-hour fire-rated demising walls (as required).

Prescriptive Fire rating of the second level floor is required to match the 2-hour floor rating for Type IA construction in Table 601. Supporting columns are considered primary structural frame and must be 3-hour rated per Table 601.
This appeal seeks to omit the rating requirements for the second level and supporting construction based on enhanced fire sprinkler design beyond the code minimum of Light/Residential Hazard. Additional fire/life safety measures include: second level is open to dwelling unit below, direct egress to public ROW sidewalk, (3-Hr) horizontal podium assembly separation from building above, and structural independence of second level construction.
See previously granted appeal 24789 Item#2 which matches this project condition.
Fire sprinklers for the units are required to be designed for Light/Residential hazard occupancy. The OH2 sprinkler suppression design is existing. This provides a far greater level of safety than minimum code requirements. The sprinklers in this portion of the building were originally designed for Group M occupancy.
Second levels are open to their dwelling area below. This will lead to quicker detection of fire by occupants of the units based on sight, sound, and smell.
Each unit exits directly to the outdoors at ground level public ROW.
The horizontal podium separation of OSSC §510.2 will protect these dwelling units from fire emergencies above.
The second level and supporting construction is independent of the building’s primary structural frame.
A similar condition (Appeal 24789, Item 2, see attached) was granted in 2021 for omission of fire rated construction of second levels in ground-floor dwelling units. The proposed design for Mississippi at Cook differs in that the existing building fire sprinkler design is more robust (OH2) than in the granted appeal which was only (OH1).
Based on demonstrated life/safety measures equivalent to or greater than code requirements, we request this appeal be granted as proposed.

2022 OSSC TABLE 601 FIRE-RESISTANCE RATING REQUIREMENTS FOR BUILDING ELEMENTS (HOURS)

Building elements are required to have a fire-resistance rating per Table 601. For Type IA construction, the following fire-resistance ratings are required:
3-hour Primary structural frame
2-hour Floor construction and associated secondary structural members

We respectfully submit this Appeal Item 2 for consideration, only in the event that Appeal Item 1 is denied. The request is to allow 1-hour rated protection of second level and supporting framing within dwelling units in Type IA construction provided fire sprinkler design is based on Ordinary Hazard Group 2 (OH2) occupancy.

The Mississippi at Cook residential mixed-use project is an existing podium-style building with four (4) stories of Type VA construction above a single story of Type IA. Occupancies include Groups A-3, B, and predominantly R-2.
Alterations are proposed to turn the existing ground-level (originally permitted as commercial space) at the SW corner into four (4) dwelling units. Three (3) of the units will have a second level that is atmospherically open to that unit below.
Plan view and section views of the units are attached.
Materials used in the second level floor/ceiling assembly will comply with requirements for Type IA construction utilizing a 2-hour rated UL H505 design. Framing will be 1-hour fire-resistance rated and will support the second level only with no floor / ceiling loads or connections to podium floor above. Existing sprinkler design was based on restaurant/mercantile (OH Group2 occupancy), and is provided throughout each unit, including below the second level. The four dwelling units will be separated by 1-hour fire-rated demising walls (as required).
See attached engineering judgment letter for fire-resistant rating of supporting structure.

Prescriptive Fire rating of the second level floor is required to match the 2-hour floor rating for Type IA construction in Table 601. Supporting columns are considered primary structural frame and must be 3-hour rated per Table 601.
This appeal requests to reduce the rating requirements for the second levels and supporting construction to 1 hour, based on fire sprinkler design beyond code requirement of Light/Residential Hazard design. Additional fire/life safety measures include: second level is open to dwelling unit below, direct egress to public ROW sidewalk, (3-Hr) horizontal podium assembly separation from building above, structural independence of second level construction.
See previously granted appeal 24789 Item#2 which matches this project condition.
Fire sprinklers for the units are required to be designed for Light/Residential hazard occupancy. The OH2 sprinkler suppression design is existing. This provides a far greater level of safety than minimum code requirements. The sprinklers in this portion of the building were originally designed for Group M occupancy.
Second levels are open to their dwelling area below. This will lead to quicker detection of fire by occupants of the units based on sight, sound, and smell.
Each unit exits directly to the outdoors at ground level public ROW.
The horizontal podium separation of OSSC §510.2 will protect these dwelling units from fire emergencies above.
The second level and supporting construction is independent of the building’s primary structural frame.
A similar condition (Appeal 24789, Item 2, see attached) was granted in 2021 for omission of fire rated construction of second levels in ground-floor dwelling units. The proposed design for Mississippi at Cook differs in that the existing building fire sprinkler design is more robust (OH2) than in the granted appeal which was only (OH1).
The column design as proposed, through installation of Type X GWB on all faces, will be protected to meet the 1-Hr minimum protection requirements under Chapter 7 of the OSSC. See attached engineering judgment letter for confirmation of fire endurance.
Based on demonstrated life/safety measures equivalent to or greater than code requirements, we request this appeal be granted as proposed.