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IBC mixed occupancy calculations
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Re: IBC mixed occupancy calculations By  BFH

Posts: 0

10/4/2006 12:43:00 PM

Slope, take each space individually. Restaurant would be 15 net (inside dimension x inside dimension) : kitchen would be 200 gross (wall-to-wall) : offices would be 100 gross (wall-to-wall). Do not use corridor or bathrooms in your calculation, these areas are for the use of the occupants and are not constantly occupied. The corridor is sized based on your occupant load as well as the bathrooms.


   

Re: IBC mixed occupancy calculations By  cda

Posts: 0

10/4/2006 1:25:00 PM

In the long run does it really matter?

I can see if you are on the border of the occupant load driving a code requirement, but that noramlly does not happen that much you are either well over the occupant load for a requriement or the opposite way under.


   

Re: IBC mixed occupancy calculations By  cserra

Posts: 0

10/4/2006 1:56:00 PM

BFH,

That makes sense, especially related to the 1997 UBC, but it seems in the IBC, bathrooms and corridors, etc. can only be excluded for net area calculations such as seating areas but not for gross area calculations such as offices. I am wondering if you have both on a floor, do you go by the largest occupancy? Therefore if it was seating you would exclude the baths and corridors, if it was offices, you would include them? Thanks for any ideas.

In my case I am on the border of a requirement to sprinkler a building.


   

Re: IBC mixed occupancy calculations By  BFH

Posts: 0

10/5/2006 4:48:00 AM

Slope, you are correct if you have a single occupancy building (i.e. office @ 100 gross) but in a mixed occupancy situation, you are looking at the different spaces on an individual basis. For example, if you had all offices on the second floor then you would use gross square footage for the entire floor, however, as in your example, if the different occupancys are all on one floor then you take the individual spaces.


   

Re: IBC mixed occupancy calculations By  Builder bob

Posts: 0

10/5/2006 6:20:00 AM

The corridors and restrooms are not normally occupied...and they would not be included in the occupant loading.(Except if your a Panther Cheerleader...then Bathroom stalls would be calculated @ 5 net.)
[IMG]http://www.websmileys.com/sm/love/144.gif[/IMG]


   

Re: IBC mixed occupancy calculations By  Code-defier

Posts: 0

10/5/2006 4:47:00 PM

Slope:

It gets even more complex when you try to do an allowable area calculation on a mixed-occupancy building...especially here in CBC land. I''m not sure how the IBC addresses this issue, but the CBC tells you that in a mixed occupancy building, one must verify that the sum of the individual allowable area ratios (e.g. sum of each occupancy area divided by the allowable for each occupancy) be less than one. I imagine that the IBC handles it in much the same way.

Here''s the rub: the CBC is silent on what to do with the "unassignable" area (e.g. corridor space, restrooms, etc. that are shared by all of the occupancies). These areas MUST be added somewhere since the allowable building areas are based on gross area, not net. I solved this problem in the past by taking portions of the unassignable area and adding it back into each assignable occupancy area in proportion to the portion of assignable area. Whew! Hope that makes sense. At any rate, I have taken this technique for a test-drive with many buidling officials and, so far, all have been in agreement that this is a logical solution to this code "gray area."


   

Re: IBC mixed occupancy calculations By  DeAngelis

Posts: 0

10/6/2006 8:54:00 AM

Actually, the CBC isn''t silent on corridors and restrooms, they''re accesory. The problem is getting the BO to understand what an accessory is.

Back in the good ol'' days, where plancheckers had some real life experience and common sense, calling toilets and conference rooms accessory to an office space was never an issue. These days, I''ve got them trying to tell me that a 180 sf conference room is an A-3 occupancy.


   

Re: IBC mixed occupancy calculations By  Code-defier

Posts: 0

10/6/2006 9:53:00 AM

Shim:

We all agree that these areas are accessory areas when related to Occupant Load calculations.

My post above was about how to go about assigning these accessory areas to the individual occupancy categories when doing an Allowable Area calculation for Mixed-Use Occupancies. CBC is silent on this issue. Every BO I have presented this to (with many actual projects) have agreed with my methodology.


   

Re: IBC mixed occupancy calculations By  DeAngelis

Posts: 0

10/6/2006 10:11:00 AM

I wish it were true that we all agree on occupant load.


   

Re: IBC mixed occupancy calculations By  Builder bob

Posts: 0

10/6/2006 10:44:00 AM

What to call a space for determination of means of egress does not pertain to the actual classification of occupancy for the building per Chapter 3. Per IBC section 1004.1, The calculations of occupant loading are based upon three design criteria.....Actual, (tabular)Design, or by combination. Regardless of which method is used, the largest number computed shall be used. Therefore, Conference rooms in a Business for purposes of egress are calculated at 15 net.The balance of the Business Occupancy will be based upon the conference room S.F. being subtracted from the gross S.F. which leaves a net S.F. for the Business Occupancy at 100 gross.
Therefore, a 751 S.F. Conference room with table and chairs would require two exits. I am not calling this an occupancy but basing the means of egress upon the actual use of this space. The overall combined spaces would be considered a B occupancy as per Chapter 3. The classification the conference room may well be B since it is accessory as spelled out in Chapter 3. But the means of egress requirements are in Chapter 10 and are a separate issue.

You cannot use chapter 3 to determine the occupant load. Chapter 10 Does.


   

Re: IBC mixed occupancy calculations By  cserra

Posts: 0

10/6/2006 11:17:00 AM

Thank you all for an interesting discussion,

I am curious to see how the Seattle BO winds up looking at this.


   

Re: IBC mixed occupancy calculations By  TJacobs

Posts: 0

10/12/2006 8:24:00 PM

[QUOTE]Back in the good ol'' days, where plancheckers had some real life experience and common sense, calling toilets and conference rooms accessory to an office space was never an issue. These days, I''ve got them trying to tell me that a 180 sf conference room is an A-3 occupancy.[/QUOTE]You mean, when there was no plan check and the BO was a retired shoe salesman and the mayor''s brother and didn''t know the difference and believed everything the architect told him...


   

Re: IBC mixed occupancy calculations By  Starbucks

Posts: 0

10/20/2006 12:25:00 AM

I do agreed with Building Bob. When determining allowable buildable area, one must first look at the building use as a whole and not an individual use. Conference room is considered accessory under code section 302.2.1, however if you have a restaurant where you have A3 and B occupancy group, and if B is less than 10% of the area of the main use, then you would considered the entire building as A3 for allowable area calculation (section 302.2). On the other hand, if exceeds 10%, then you''ll need to use unity check where sum of both occupancy group must be less than one.

As far as distributing floor area in corridor and bathrooms, I would consult with local building official since every city has their own interpretation.

Starbucks


   

Re: IBC mixed occupancy calculations By  thelunatick1

Posts: 0

10/23/2006 10:10:00 AM

I know the conversation is IBC 2003.
But 2006 altered the label used inthe first column of table from "occupancy" to "Function of Space".

However I don''t beleive "Function of Space" is used anywhere else in chapter 10 dealing with this table. And thus came a bit short in dealing with the explanation of "function of space".

It would be nice if chapter 10 had sections that dealt with "incidental" and "accessory" uses. Say does a corridor in a school be based upon E even though the facility is mixed with A and B occupancy types.

If you think it help, we could start a thread to specifically discussing this in an effort to submit a proposed change for or interpretation of the various I Codes.


   

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