# Large Lobby in a B, does it become an A



## FyrBldgGuy (Nov 29, 2009)

The building is a business occupancy with a large three story atrium lobby.  The lobby is shaped like a round hub. The primary purpose of the lobby is access to four wings.  The public enters the lobby to access payment windows for the primary business.  The lobby has some artwork and displays for educational purposes.  One of the wings has a meeting room capable of holding 157 occupants.  The meeting room is not separated from the lobby by rated construction.  There are no occupancy separations throughout the building.  Under the 1991 UBC the lobby was classified as an A3, but based on square footage the occupancy load would be more like 1600 people.  A few times a year the lobby is used for public informational events, where hundreds of people gather.

If the purpose of a lobby to provide a pathway to the primary occupancy should the Occupancy classification been the same as the primary occupancy?  How would you classify the lobby today?


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## RJJ (Nov 29, 2009)

Re: Large Lobby in a B, does it become an A

Is there some reason that the occupancy would be being changed. Major alteration etc. Or is a problem existing on how it is being used. What code is in effect now?


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## north star (Nov 30, 2009)

Re: Large Lobby in a B, does it become an A

*FyrBldgGuy,*

*Suggest that your building be assigned a correct "use of space" for the*

*atrium area in question.   Sounds like that area is an A-3 to me!*


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## Gene Boecker (Nov 30, 2009)

Re: Large Lobby in a B, does it become an A

FyrBldgGuy,

How did you get an occupant load of 1600?  Was that using 100 sf/occ. (business) or 5 sf/occ. (standing space)?

If the main use of the space is circulation for business, then it's a 'B' occupancy.  However, if the large gatherings are a part of the regular planned activities for the space then it needs top meet both B and A requirements according to 302.1 (2006 edition and later).  Otherwise it can be simply B and the assembly function can be treated as a special event and regulated under 403 of the IFC.

I'm not sure that the end result will be much different but it allows some flexibility in the way it's handled.


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## RLM-Architect (Dec 9, 2009)

Re: Large Lobby in a B, does it become an A

The atrium in a Group B is still Group B unless Group A activities are introduced (like a New Year's Eve rock band event)


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## FyrBldgGuy (Dec 9, 2009)

Re: Large Lobby in a B, does it become an A

A group M could have a holiday sale with a choir, does that make it an A?  Or unless the primary purpose is an A it should be what ever the primary group is; and any special event handled by the Fire Code.


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## vegas paul (Dec 9, 2009)

Re: Large Lobby in a B, does it become an A

Keep in mind that the occupant load is independent of the occupancy classification.  Even if it remains a B occupancy, the occupant load is based on the function or use of the space.  You can have 5 s.f. (standing), 7 s.f. (seated-chairs) and/or 15 s.f. (tables and chairs) per occupant in any occupancy classification.


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## Big Mac (Dec 9, 2009)

Re: Large Lobby in a B, does it become an A

From the original posting

"A few times a year the lobby is used for public informational events, where hundreds of people gather."

Sure sounds like an A-3


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## FyrBldgGuy (Dec 10, 2009)

Re: Large Lobby in a B, does it become an A

Occupancy Load and Occupancy Classification are different but still related.  Because the Lobby is used as a means to go from one wing to another there are few if any chairs, tables, etc.  There is a payment window where upto 20 people may be standing in a line.

The original architect wanted to a have a large sunlight wide open space as a transition.  So the space can be used for other functions.

If the Lobby stood on its own it would look like a bank teller area.


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