• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

Assembly occupancy - 66% occupants one direction?

D

doregan

Member
Joined
Feb 15, 2010
Messages
9
Hi all,

I have an assembly occupancy atop 4 levels of Business occupancy - level 5 is conferencing and bar.

All B occupancy floors can adequately be served by 2 stairs. To ensure maximum usable square foot at top level A occupancy I propose to add a stair - grouping 2 stairs at one location and the other separated by half the diagonal.

Is it a problem to have 67% of occupants served in one direction and 33% in other? I would be using all the required stair width (5350 sq.ft. - 0.37" per occupant - 3 No 44" stairs).

We fall under SBCCI 1999 Standard Building Code

Thanks in advance for your usual excellent input.
 
what is your occupant load???????

welcome if it has not been extended to you
 
Thanks for the Welcome cda - I have been lurking and searching this forum and the ICC one before it became an unhelpful animal for a few years now. Posted the odd query too. Not being a code professional I am one of those that normally don't feel qualified to weigh in on the topics - but I do read them with interest.

Occupant load on heaviest populated floor (top level - A assembly) = 350 occupants (5250 sq.ft.). I haven't thoroughly worked out the floor yet - wanted to know if the principle is sound before going back to the drawing board.
 
Assembly on level 5 of a 5-story building? The first check may be allowable height of the Group A based on the existing construction type.

Assuming the only code issue is the number of exits, where the elevator is the main entrance, it would seem your building could apply the exception to 2009 IBC 1028.2. However, it is not immediately evident that a new stair immediately adjacent to an existing stair would satisfy the intent of "distributing" the exits around the perimeter. Maybe if the access to the new stair were on the opposing side.
 
The thing about it is you must provide a specific anount of exits. If two are required then they must be calculated so that 1/2 of the occupant load can exit through each exit. If you are trying to calculate widths by saying that 66% of the OL will exit through a specific exit and the other 34% will go through the other exit and size it accordingly then that won't work! Who is going to count the occupants...Okay.....#34 ... that's all!!!! the rest of ya'll have to go the other way!!!
 
doregan said:
Thanks for the Welcome cda - I have been lurking and searching this forum and the ICC one before it became an unhelpful animal for a few years now. Posted the odd query too. Not being a code professional I am one of those that normally don't feel qualified to weigh in on the topics - but I do read them with interest. Occupant load on heaviest populated floor (top level - A assembly) = 350 occupants (5250 sq.ft.). I haven't thoroughly worked out the floor yet - wanted to know if the principle is sound before going back to the drawing board.
Click to expand...
I've got 750 occupants for a 5250 sf conference room.
 
Mule - that is what I was thinking - how do I govern the exit direction. The 2 stairs grouped does not cater for the "distribute exits around perimeter" requirement and does not. It is a tricky one and I wont drop the idea just yet - but there is always another solution.

In terms of building type and occupant calculation I am fine - 15sq.ft. per person net is what is mandated locally - I believe I even have a bit of wiggle room.
 
doregan said:
Mule - that is what I was thinking - how do I govern the exit direction. The 2 stairs grouped does not cater for the "distribute exits around perimeter" requirement and does not. It is a tricky one and I wont drop the idea just yet - but there is always another solution. In terms of building type and occupant calculation I am fine - 15sq.ft. per person net is what is mandated locally - I believe I even have a bit of wiggle room.
Click to expand...
Doesn't matter what is mandated locally, there is no way that a conference room that big is always going to have people sitting at tables, that's why the code requires 1 per 7 sf.
 
You didn't mention what code edition you are using. The 2009 IBC, Section 1028.2 states "Group A" occupancies ................... having an occupant load of greater than 300 shall be provided with a main exit. The main exit shall be of suffcient width to accomdate not less than 1/2 the occupant load, but such width shall not be less than the total required width of all means of egress leading to the exit."

Having said that, I think I would furhter explore whether or not an occupant load factor of 1:15 is appropriate for the intended use. Is this space really never going to be used for just removeable or temporary chairs? I would tend to error on the side of caution where occupant load is concerned.
 
AegisFPE said:
However, it is unclear how a change of use today could be under a legacy code from over a decade ago.
Click to expand...
Until last November (2010) our State Fire Marshal enforced SBC 1997 when there was not a local jurisdiction.
 
The older versions of SBCCI had a requirement for assemblies where :

1. Main exit must provide 50 of the egress capacity

2. remainder of exits must provide 67% (2/3) of the required width for occupant load egress

Sbcci worked off of occupant for designed egress but allowed occupant content to be posted for a room based upon the amouont of egress width provided. Therefore, a occupant load for an assembly of 1500 SF w table and chairs would have a occupant load of 150 with a required egress width of X number of inches. If the room has three 32" clear width doors, I could post an occupant content of 480...... approx 160 per door.
 
Been under the SBC for many years, your occupant load would be calculated using the worse case. 15-sf per person is not the worse case. What AHJ is still using the 1999 SBC?
 
Examiner said:
Been under the SBC for many years, your occupant load would be calculated using the worse case. 15-sf per person is not the worse case. What AHJ is still using the 1999 SBC?
Click to expand...
Here's a question, what is so much better about the current IBC than SBC 1999?
 
For many years many have tried to have one code to go by. As an Architect I have been under all the Building Codes and Life Safety Codes at one time or another and had to work with AHJ's using different codes and different years. It is good to have one code now that everyone can use. However, I still have to contact the AHJ's to see what year and any amendments. One code is good so the interpretations usually stay the same and everyone can be on bascially the same page.
 
That doesn't make the code better. Everyone could have adopted NFPA 5000...or SBC for that matter.
 
NFPA did not want to merge due to money issues they saw as loosing. So they did there own Building Code and it is close to the IBC. I have a project with the Bureau of Indian Affairs and that Federal Agency uses the NFPA 5000 Building Code. Makes you wonder what politician got a donation to get that code in the Feds when the other agencies use the IBC.

Just would like to have one code to use and not have a library with multi codes. You AHJ's only have one to deal with while we Architects and other Professionals have to have copies of many others and know them. Oh, I am an employee of a firm and no, Architects do not make a lot of money especially as an employee. I was falsely led by the Mr. Ed and Brady Bunch shows in my youth.
 
NFPA did not merge because the process which was proposed by the ICC and which is still in place today did not meet their standards - standards which the NFPA has established over more than 100 years of it's existence and which are generally accepted by all interested stakeholders and make for sound well reasoned code changes.
 
"Mule - that is what I was thinking - how do I govern the exit direction."
Click to expand...
Wouldn't the illuminated Exit signs govern the exit routes? Occupants could choosetheir own exit, but I do not believe that an actual occupant count limit can be

( realistically ) enforced.

.
 
Thanks again all for your insights. The scheme has been abandoned due to reasons other than code related - but this may be an option in a future design we are considering. I still believe that 15 is the occupant load assigned to conference rooms under unconcentrated assembly occupancy - 7 being assigned for concentrated. I will pledge to look further into this with AHJ before developing the scheme any further.

As to what jurisdiction - I am in the Cayman Islands - so we have an altered version of the 1999 SBCCI.
 
You must log in or register to reply here.
Top