Mezzanine grows and becomes a second floor

[BayPointArchitect]

Given:
A nonsprinkled office space with an upper level mezzanine would like to expand the mezzanine into an adjacent tenant space. But then the area of the mezzanine will exceed the allowable ratio when compared to the open and unobstructed area below. Therefore the upper level will become a second story rather than a mezzanine. The mezzanine is surrounded by a guard rail and the stairway is open / unenclosed.

Question:
After establishing that the upper level is no longer a mezzanine and is now a second floor, what sections of the IBC building code and NFPA life safety code requires these two levels (both office spaces) to be either fire and/or smoke separated?

Thanks in advance.

ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner

 

[steveray]

None...Other than looking at the egress and height and area and making sure it meets the requirements for a two-story building.....

 

[RLGA]

There are no requirements for atmospherically-connected two-story spaces as long as they meet the criteria of IBC Section 712.1.9. However, as @steveray states, you now need to consider the allowable height and area (mezzanines do not contribute to building area or height in stories) for the occupancy and construction type.

 

[walker.t]

expand the mezzanine into an adjacent tenant space

Is the mezzanine open to the adjacent tenant space? Sounds like you’re combining two tenant spaces if they are connected by a mezzanine.

what sections of the IBC building code and NFPA life safety code requires these two levels (both office spaces) to be either fire and/or smoke separated?

Now that it’s a story you have increased the building area and need to confirm if there is any impact on non-separated occupancy (IBC 508.3) or separated occupancy (508.4) if applicable. Also confirm if the increase in mezzanine area increases the fire area to a point where you need sprinklers per IBC 505.2. Other than that I can’t readily think of anything. I can’t comment on NFPA requirements, someone else will have to comment on that.

 

[steveray]

And to expand a little....as a story you may need a rated stair now....CT is really tough on exit access stairs..

 

[BayPointArchitect]

There is no issue with allowable area or height or maximum stories. The space that we are expanding into is a small room and the main structure of the building is reinforced concrete. The adjacent space that we are expanding into is fire sprinkled. The office area is non-sprinkled. So that’s a little weird.

 

[Yankee Chronicler]

How is the building not already a 2-story building?

 

[BayPointArchitect]

This is a three-story building with multiple tenants. According to 2018 IBC Table 504.4, three stories is the maximum for a non-sprinkled S-2 occupancy, Type IIIB construction with the exterior bearing walls being two-hour fire-rated cast-in-place concrete and nothing else fire-rated. And the same is also true for a B business occupancy. According to IBC Table 504.3, the maximum height is 55 feet which is more than the actual height of 35 feet. According to IBC Table 506.2, the maximum allowable area is somewhere between 19,000 S.F. and 26,000 S.F. And with 50% area separation increase, the allowable area is 57,000 S.F. That is more than the actual 33,300 S.F. There are no issues with IBC Chapter 5 height and area. Again, I say that building height and area are okay. The tenant spaces are separated by 12 inch thick brick walls and the floors consist of concrete twin-tees with concrete topping.

 

[walker.t]

A nonsprinkled office space…what sections of the IBC building code and NFPA life safety code requires these two levels (both office spaces) to be either fire and/or smoke separated?

You asked about fire separations, but what about the requirement that the building be sprinklered per 2018 IBC 903.2.10 Point 2 “Where the enclosed parking garage is located beneath other groups.”? Your section sketch shows enclosed parking below the expanded office space.

 

[LR419]

Is the second floor area that's being expanded into an existing office use? If not, refer to IEBC Chapter 10 for the change of occupancy provisions. If it is currently an office use, refer to IEBC for the applicable compliance method for the alterations. IEBC may or may not send you to IBC 903 for the sprinkler requirements, and may or may not require the allowable area calculation.

If the allowable area does need to be considered, check your math on the increase. The maximum frontage increase (if 100% of the perimeter has an open space width of 30 feet or more) is 75% of the base area of 19,000 (the most restrictive applies per IBC 508.3.2), or a total of 33,250 per floor. It's not clear where the 57,000 is coming from or what the 50% area separation increase refers to.

 

[BayPointArchitect]

Thanks Walker. I need to change my sketch to show that area below the expanded office as showers and restrooms for a Yoga Studio.

LR419, your comment about change of use per IEBC is valid. The local plan reviewers are killing projects for existing buildings. They are requiring that existing buildings be brought up to current code in every aspect and every detail. Potential tenants who want to take an existing "B" occupancy and sell merchandise as an "M" without making any changes to the building are forced to walk away from an old vacant building that was fully functional for the previous tenant.