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Does Mechanical Penthouse count against Building Height on Table 504.3?

lenny

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Jul 28, 2022
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5
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NY
Asking a question on a building in NYS. It is 4 stories of B occupancy over 1 basement story of S-2 parking.

Table 504.3 allows for a type IIIB occupancy as long as the building is only 75' above the grade plane. The mechanical penthouses are pushing this limit. They are code-defined penthouses, only air handlers and nothing else in them. They are also less that 30% of the roof area.

I can't find anywhere in the code that states the penthouse area can be exempted from the building height. It would seem logical though based on all the other exceptions and limitations on the penthouse per code. Didn't see anything on commentary either.

Does the penthouse height count against the building height in table 504.3?
 
my interpretation is that per 505.3, a mechanical penthouse does not count towards the number of stories or the overall height limitation. it would probably be a good idea to find out who the ahj is that will be reviewing the project and ask them.
 
my interpretation is that per 505.3, a mechanical penthouse does not count towards the number of stories or the overall height limitation. it would probably be a good idea to find out who the ahj is that will be reviewing the project and ask them.
505.3 in the 2020 BCNYS is an equipment platform: https://up.codes/viewer/new_york/ibc-2018/chapter/5/general-building-heights-and-areas#505.3

In this case I'm looking at enclosed penthouses: https://up.codes/viewer/new_york/ibc-2018/chapter/2/definitions#202

[BG] PENTHOUSE. An enclosed, unoccupied rooftop structure used for sheltering mechanical and electrical equipment, tanks, elevators and related machinery, and vertical shaft openings.
 
I'm not sure if NY modifies it, but IBC 1510.2 says:

"Penthouses in compliance with Sections 1510.2.1 through 1510.2.4 shall be considered as a portion of the story directly below the roof deck on which such penthouses are located. Other penthouses shall be considered as an additional story of the building."
 
505.3 in the 2020 BCNYS is an equipment platform: https://up.codes/viewer/new_york/ibc-2018/chapter/5/general-building-heights-and-areas#505.3

In this case I'm looking at enclosed penthouses: https://up.codes/viewer/new_york/ibc-2018/chapter/2/definitions#202

[BG] PENTHOUSE. An enclosed, unoccupied rooftop structure used for sheltering mechanical and electrical equipment, tanks, elevators and related machinery, and vertical shaft openings.
that's a valid point. i was thinking of the penthouse as an enclosed equipment platform. i should have read chapter 15 first.
as Paul says, 1510.2 is more to the point. if you comply with 1510.2.1 through 1510.2.4 then it is not a story and you are permitted 18 feet for the additional height of the penthouse.
 
that's a valid point. i was thinking of the penthouse as an enclosed equipment platform. i should have read chapter 15 first.
as Paul says, 1510.2 is more to the point. if you comply with 1510.2.1 through 1510.2.4 then it is not a story and you are permitted 18 feet for the additional height of the penthouse.
So even though its not directly stated, the 18' height allowance strongly implies that penthouses do not count against the 'Allowable Building Height in Feet Above Grade Plane (Table 504.3)'. Agree/Disagree?
 
So even though its not directly stated, the 18' height allowance strongly implies that penthouses do not count against the 'Allowable Building Height in Feet Above Grade Plane (Table 504.3)'. Agree/Disagree?
agree. I think the code is fairly clear but i'm a big believer in reviewing questions like this with the ahj early on before submission so that you're not hit with any surprises when you get your code review back. i would consider being told that you have to take a story off your building as a pretty major surprise. always do your homework first before going to the ahj which is why i'm on this site.
 
Not NY code but here is the 2018 IBC:

504.3 Height in feet. The maximum height, in feet, of a
building shall not exceed the limits specified in Table 504.3.

Exception: Towers, spires, steeples and other roof structures
shall be constructed of materials consistent with the
required type of construction of the building except where
other construction is permitted by Section 1510.2.4. Such
structures shall not be used for habitation or storage. The
structures shall be unlimited in height where of noncombustible
materials and shall not extend more than 20 feet (6096
mm) above the allowable building height where of combustible
materials (see Chapter 15 for additional requirements).
 
Not NY code but here is the 2018 IBC:

504.3 Height in feet. The maximum height, in feet, of a
building shall not exceed the limits specified in Table 504.3.

Exception: Towers, spires, steeples and other roof structures
shall be constructed of materials consistent with the
required type of construction of the building except where
other construction is permitted by Section 1510.2.4. Such
structures shall not be used for habitation or storage. The
structures shall be unlimited in height where of noncombustible
materials and shall not extend more than 20 feet (6096
mm) above the allowable building height where of combustible
materials (see Chapter 15 for additional requirements).
Thanks. So there is plenty of reasoning within IBC 2018 to interpret that the penthouse does not count against the building height. Out of curiosity, how would you present something like this? I would inform the AHJ of the interpretation and ask if they agree. This is my first time posting anything here, curious to see what you would do.
 
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