Calculating Room Capacity

[JVV]

We are looking to turn our Dance Studio into a performance space for our Spring Arts Festival. The Facilities Manager does not currently have a seating capacity for the room and while he works on obtaining that from the Fire Marshal, I figured Id ask if anyone knows what goes into determining that number. The room is 30' x 50' with double doors (both with exit sign above them) at opposite sides of the room. One door goes back into the Hallway, one goes outside. There is also a single door that goes into the Drama Room that also has two points of egress. This is a fairly new space (5 years) so there is a sprinkler system, HVAC all that good stuff.

For this specific event we will have a performance space that is roughly 19'deep x 24'wide and keep 24" between rows with at least a 4' aisle between seating sections. We are going to set up the same folding chairs that are set up for Graduations and Assemblies in the Gym (they do not lock together...)

Is there anything else to take into consideration?

[tjrobb]

Per code, assemblies of that nature are 7 square feet per person, rounded up. IE, capacity = SF / 7. This is also true of stages, FWIW.( This is just for exit capacity, good luck actually getting that many in there.)

[museav]

Per code, assemblies of that nature are 7 square feet per person, rounded up. IE, capacity = SF / 7. This is also true of stages, FWIW.( This is just for exit capacity, good luck actually getting that many in there.)

Building Code for most venues is defined at the county or municipal level so is that based on the applicable code for their jurisdiction?

Where I live is a pretty good example of the potential issues this causes. The County is the AHJ and in terms of fire safety standards the County Ordinances adopt the State minimum standards. In turn, the State Construction Codes Minimum Standard Codes reference IFC 2006 with 2007 and 2010 State amendments. So what is applicable here is apparently neither any version of NFPA nor the current IFC 2012 version, but rather an older IFC version with amendments. The same general issues can apply to other aspects of building codes, what is applicable can vary significantly from one location to another. This is why code questions can be so difficult and are best answered by someone familiar with what codes and amendments are applicable.

One thing to consider is whether the change in use may represent a change in occupancy classification. That may not be applicable but there could also be a chance that it might represent going from something like an educational or business classification to a public assembly classification. The factor there is often what classification was used or assigned during the original construction as it is not that unusual to try to get a more lenient classification to reduce construction cost, which may then limit the potential changes without reclassification.

As far as what goes into determining occupancy, there may be some minimum per person numbers but there will also be factors such as exiting requirements that could affect seat spacing, numbers of contiguous seats allowed, aisles sizes and so on. And an important aspect that the Fire Marshal may not address is accessibility and ADA compliance which can involve handicap seating provisions, wheelchair access, objects of intrusion, Assistive Listening Systems and so on. These aspects can also 'piggyback' onto life safety requirements, for example if a life safety exit involves stairs then there may need to be special accommodations made to make that an accessible exit.

[tjrobb]

Ah, yes, was only reading part of it. My original post was only the stage; I know here we take the whole space as a "studio theatre" and use the 7 sf regardless of actual chair count.
Most, if not all, theatres will require more than 24" between rows, no one over 6' tall will fit and its too narrow for egress.
Also, most times the chairs need to be locked together, a friendly AHJ will let you zip-tie them. This keeps them from wandering and blocking an aisle.
Beyond the generic requirements herein, you should probably be talking to your AHJ, they have to approve it anyway and tend to be friendlier when approached early on.

[MPowers]

Room Capacity is determined by many things Square feet per person is just one. A major component is egress and that has many parts. the following is just the table of contents from the NFPA 101 2000 life safety code

Chapter 7 Means of Egress

7.1 General
7.2 Means of Egress Components
7.3 Capacity of Means of Egress
7.4 Number of Means of Egress.
7.5 Arrangement of Means of Egress
7.6 Measurement of Travel Distance to Exits
7.7 Discharge from Exits
7.8 Illumination of Means of Egress
7.9 Emergency Lighting
7.10 Marking of Means of Egress
7.11 Special Provisions for Occupancies with High Hazard Contents
7.12 Mechanical Equipment Rooms, Boiler Rooms, and Furnace Rooms
7.13 Normally Unoccupied Building Service Equipment Support Areas
7.14 Elevators for Occupant-Controlled Evacuation Prior to Phase I Emergency Recall Operations

below a partial table from section 7.3

Table 7.3.1.2................. Occupant Load Factor
Use .................................................. ......................................(ft2 / person)
Assembly Use

Concentrated use, without fixed seating ...................................7 net

Less concentrated use, without fixed seating...........................15 net

Bench-type seating........................................... .........................1 person/ 18 linear in.

Fixed seating........................................... ...................................Use number of fixed seats.

In addition the size and category of the exits can reduce the occupancy rating of a room. For a size example, if the Super Dome only had one 3' wide door for an exit, the occupancy would only be about 100 people (depending on jurisdiction). If the same super dome had 50 doors a 6' wide but the led to a hall 100' long which led to a stair which led.... Then again the category rating might drop the occupancy to 100 or less.

On another point, 24" spacing, do you mean from the back of one seat to the front edge of the next row? I hope so, as 24" is far too close. Rows are usually measured back to back. That is, from the center back of a seat to the center back of the next row. 36" is common, 39" is far more comfortable and allows patrons to enter and exit without seated patrons being forced to stand.

[JVV]

Yes. I was thinking 24" from the seat of one chair to the back of the one in front of it.

[JLNorthGA]

One thing to take into consideration is air conditioning and HVAC capacity. A "stuffy" space does not bring people back. Also, a lot of people generate a LOT of heat. So remember, with the people, dancers and lighting, you have a lot of heat. I would get your HVAC looked at and evaluated.

Just saying...

[museav]

One thing to take into consideration is air conditioning and HVAC capacity. A "stuffy" space does not bring people back. Also, a lot of people generate a LOT of heat. So remember, with the people, dancers and lighting, you have a lot of heat. I would get your HVAC looked at and evaluated.

Just saying...

A very good point. An increase in rated capacity for a space can affect not just HVAC, life safety and so on for that room but if it affects the overall capacity of the building at any time then it potentially also affects aspects such as restrooms and parking for the venue.