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Building separation

bldginsp

bldginsp

Bronze Member
Joined
Oct 22, 2009
Messages
68
Location
Eastern US
Question came up in our bldg office if a building can have more than one construction type if built on top of each other. Example, a developer wants to build a M use group below a R-2 use group, wants the M to be 1A and the R-2 to be 5A. Look like 602.1 of the IBC states only one of the five types shall be used. Can't be considered two separate buildings because of being stacked and can't meet the defination of fire wall but could if side by side. Thoughts.
 
98 % correct. A building is permitted to have one type of construction on top of another type of construction in accordance with Section 509. I refer to this as the Type I-A "table" with residental units of II-A or V-A above.
 
I see Section 509 but I don't see where it is required to have II-A or V-A above. I see that it requires the most restrictive fire separation for the floor assembly separating the two uses. Where am I missing the 2 or 5 A?
 
509.2 permits any type of construction to be built on top of Type I-A. I have done many of these and the most common construction type on top of the Type I-A is II-A or V-A.
 
Coug Dad said:
509.2 permits any type of construction to be built on top of Type I-A. I have done many of these and the most common construction type on top of the Type I-A is II-A or V-A.
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But it seems to me that the title of 509.2 and condition #4 within that section would prevent it from being used in the scenario described in the OP where the bottom portion is an M occupancy and the upper portion is R-2.
 
Group M is one of the occupancies allowed under the "table". The question is if they would have to provide parking for at least one car to be in compliance with the provision.
 
Group M is one of the occupancies allowed under the "table".
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What "table" are you refering to?

509 is for parking garage below Group A, B, M, R or S occupancies

or 509.8 Group B or M with Group S-2 open parking garage above.

Under to OP a M below and a R-2 above the height and area would be restricted to 506.4.1 Mixed occupancies and subsequent referenced sections.
 
Section 509.2 establishes the three hour "table" with Type I-A constructon below, and some other construction above. Section 509.2 (4) exception 2 limits the occupancies under the "table" to S-2 parking, B, M, and A with less than 300 occupants. The area above the "table" is limited to Group B, M, R, S, or A with less than 300 persons by Section 509.2(3). The question I posed was do you have to provide at least one parking space below the "table" to use this provision.
 
The question I posed was do you have to provide at least one parking space below the "table" to use this provision.
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I am following you now and I believe the answer is No a parking space is not required.

I think exception 2 is pretty clear in it is an exception to the requirement of having an open or closed parking garage. Although the commentary does not support this I believe the "literal" wording in the code does

The commentary states "the exceptions to Item 4 indicate the conditions by which uses other than parking can be located on the same level as the enclosed parking garage"

509.2 is enclosed and open parking garages, the commentary only reference enclosed parking garages
 
mtlogcabin said:
I am following you now and I believe the answer is No a parking space is not required.
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Ok, I'm following Coug Dad's reasoning better now too, but I still believe that you would need to provide some parking below the separation. 509.2 is for "S-2 enclosed or open parking garage with Group A, B, M, R, or S above." If you don't have a parking garage below, you can't even get to Section 509.2. Once you get there, then exception 2 to Item 4 opens the door for other things in addition to the parking.
 
FYI, we've had a lot of this kind of construction in Southern California. Most people out here refer to it as "podium" construction, because saying the word "table" in a code discussion is like saying "Who's on first?".
 
My take on 509

509 exempts or modifies the allowable height and area based on occupancy and construction types

509.1 General.

The provisions in this section shall permit the use of special conditions that are exempt from, or modify, the specific requirements of this chapter regarding the allowable heights and areas of buildings based on the occupancy classification and type of construction, provided the special condition complies with the provisions specified in this section for such condition and other applicable requirements of this code.

509.2 requires all 5 requirements to be met

509.2 Group S-2 enclosed or open parking garage with Group A, B, M, R or S above.

A basement and/or the first story above grade plane of a building shall be considered as a separate and distinct building for the purpose of determining area limitations, continuity of fire walls, limitation of number of stories and type of construction when all of the following conditions are met:

Requirement #4 is the building below the horizontal assembly be a Group S-2 parking garage

4. The building below the horizontal assembly is a Group S-2 enclosed or open parking garage, used for the parking and storage of private motor vehicles.

Exception #2 provides for additional limited Occupancy Groups if protected by an approved automatic sprinkler system.

Exceptions:

2. Multiple Group A uses, each with an occupant load of less than 300, or Group B or M uses shall be permitted, in addition to those uses incidental to the operation of the building (including storage areas), provided that the entire structure below the horizontal assembly is protected throughout by an approved automatic sprinkler system.
 
The 2009 IBC revises this horizontal separation provision slightly to explicitly permit those referenced in Item 4, plus Group R and incidental building uses, clarifying that parking area should not be required.

If it's a short building, be careful with the shaft enclosure ratings per Item 2!
 
AegisFPE said:
The 2009 IBC revises this horizontal separation provision slightly to explicitly permit those referenced in Item 4, plus Group R and incidental building uses, clarifying that parking area should not be required.
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Thanks for pointing that out. The 2009 won't be the official code in Utah until July, so I'm still learning all of the changes. The new language does clear it up.
 
"Podium" is probably a better word than "table." I typically use "table" because I am usually explaining the concept in a conference room and I use the conference room table as my three hour separation. Under the "table" is parking and on top of the "table" is residential. I have worked on many of these buildings and it is always fun to explain the concept to someone who has never done it. The "table" analogy makes it easier. The light goes on and people realize what the code permits.

This all tracks back to studies that were performed on affordable housing. Higher density "urban villages" could be created if residential units on top of parking garages could be constructed of more conventional construction, which kept the costs lower as comparted to Type I-B construction. Retail, small restaurant, and office occupancies were permitted under the podium to encourage an enlivened urban street front. Rents charged to commercial tenants would also help offset the common area maintenance costs.
 
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