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How Much Space is enough?

Posted on June 21, 2006

Today we are going to talk about putting your meeting into a space. Not outer space, although sometimes I wonder.

Most ballrooms are rectangular. A few are square. Fewer still are curved. Some are oval, although oval and rectangular operate on the same principles as far as I am concerned. They are just a little weird for my taste. I once drew a floor plan for a meeting room that was crescent shaped. That was a beast since the hotel's capacity chart did not allow for projection.

If all of your meetings involve fewer than fifty people or if they involve no audio or video, you can stop reading. If all your events are social events that are primarily food functions with or without dancing you can stop reading. None of what I am about to say will materially impact anything you do. Sorry, but that is a huge segment of the industry where I do not play. Not that I don't want to, but one goes where the opportunities lead. My opportunities pointed in another direction.

For the rest of you who are still with me, get your calculators out. How many people can you seat in a ballroom that is 100' X 200'? This ballroom is 20,000 square feet. At one person for every ten square feet as some of the publications would have you believe, that's 2,000 people. Very nice! Your meeting only has 1,600 people. It should fit nicely.

The good news is that there are no pillars. Subtract between 10 and 20 people for every pillar.

Of course, the ten square feet per person calculation does not allow for aisles. In most jurisdictions, you need to be at least six feet away from the walls. 6' X 200' X 2 = 2,400 square feet of usable space we have lost against the long walls. 6' X 88' X 2 = 1,056 square feet of usable space we have lost against the short walls. Therefore, our 20,000 square foot ballroom actually has 20,000 – 2,400 – 1,056 = 16,544 square feet of usable space. At ten square feet per person, we still have room for our 1,600 people.

The fire marshal is not likely to approve your floor plan without a 6' aisle. 6' X 188' = 1,128 square feet. So, our 16,544 square feet of usable space has shrunk to 15,416 square feet and we have dropped below our desired attendance count.

Let's toss another issue into the mix. 100 square feet (ten square feet per person at round of ten) is not enough for a 72" round with more than six people seated at it.
Let me explain. The table takes six feet. That leaves four feet for the people seated at it before they run into the space allocated for the adjacent table. That's two feet on each side. The proverbial 98 pound weakling has a thickness at their chest in excess of a foot. If they elect to not jam themselves against the table, they will take perhaps eighteen or twenty inches of depth away from the space around the table. We do that on both sides and we have lost three or more feet. The back of the chair is now less than a foot away from the chair behind it. If either of the people seated with their backs to each other weighs in excess of 150 pounds, they will take all the space allocated.
The wait staff can no longer pass between the tables.
This is one of the reasons I advocate using real Computer Aided Drafting programs that work in 


WORLD SCALE for floor plans. As far as I am concerned, you should allocate a minimum of 121 square feet per table. 144 is better, but 132 will work. Our count continues to drop.

So, we have sixteen hundred people in this room for a couple of hours. What are they doing? Are they dancing? Is there a program? Let's assume that we have a D J and a dance floor. The D J stage is 12' X 16' and the dance floor is 30' X 30'. We can shove the D J back against the wall so we regain part of the stage area. Even with that, we have lost 6' X 16' = 96 square feet for the stage. We lose 30' X 30' = 900 square feet for the dance floor. So our ballroom continues to shrink. 15,416 square feet – 96 – 900 = 14,420 square feet. Remember that this puts three entire rows of tables behind the dance floor.

Now let's make things really complicated. We have an audio visual presentation and a name entertainer at dinner. At this point we start over. Many meeting planners like to set their stage against the long wall. This is what I refer to as the "wide" configuration. They feel that this gives a feeling of intimacy. Perhaps, but let's look at the numbers. The video screens need twenty feet of depth and no one can be behind them. Our 100' X 200' ballroom is now effectively 80' X 200' or 16,000 square feet. Not bad? Maybe, maybe not. We still need to subtract for aisles and the stage. Our 16,000 square feet drops to 13,936. Not only that, we are looking at a control booth of some kind that will eat up space. One fifth of the audience is at such a steep angle to the screens that the screens are unintelligible. Depending on the depth of the stage, up to a third of the audience is behind the speakers and they can't hear.

Remember that there are events for which it is not important that everyone see or hear what is happening on the stage. Networking events and incentive events without awards programs are two excellent examples. For those events, the inability to see or hear the program is an advantage. Pools of quiet are created where business can be conducted during the party.

Let's spin the room the other way. If we set with the stage against the short wall, accounting for the projector throw distance the room is now 100' X 180' = 18,000 square feet before we lose the space along the walls and the aisles. Our 18,000 drops to 15,840 which is significantly better than 13,936. I refer to this as the "deep" configuration. We do have a slight issue in that our furthest audience member is 160' from the stage, but the good news is that no one is behind the stage. The rule of thumb is that an audience member watching a properly lit actor can see facial expression up to eighty feet away. Remember the Metallica concert I mentioned yesterday? I was over three hundred feet away. From a technological point of view, deep is easier to deal with than wide. First, we step up to larger screens, image magnification and brighter projectors. For audio, we go to line arrays and delay speakers. Lighting gets a little brighter.

If the ceiling height prohibits larger screens, then delay screens (smaller screens with smaller projectors) can be flown mid way back. With the advent of brighter projectors and speakers with longer throw, the "deep" configuration is the most efficient way to use the available space in the room.

Let's return to our event and add a stage. With the dancers and the singer's band, the stage needs to be 32' deep and we do not want anyone behind the speakers. In the wide configuration, we now have a room that is effectively 62' deep by 188' wide for 11,656 square feet. The center aisle is not an issue because we can only set six rows of tables. If we go to the deep configuration we have a room that is 88' wide by 162' deep or 14,256 square feet.

All of the examples assume that the event is a plated sit-down meal. If the event is a buffet, you will lose some of the space to the buffets and bars. The good news is that the buffets and bars can go in the six foot margin and you lose less space than is immediately obvious.

Remember the theme of listening to your vendors? National Production Services is one of my vendors. They provide rigging services in a wide variety of venues.


For those facilities in which they work, they have the best information about the actual sizes, shapes and ceiling heights of the rooms you are most likely to use. These drawings are in a computer aided drafting program. There are two such programs that compete in this industry. The more established program is AutoCAD which has been the mainstay of the architectural industry for decades. The newer entry into the field is Vectorworks which is gaining acceptance in part due to its significantly lower cost and more "Mac-like" interface.

There are a dozen software packages out there that can handle a table set up for a social event with a stage and a dance floor. You can place the bars and buffets with them. You can even determine where you want to put the cake table. (Digression: Light the cake table. Spend the money. It's important.) For social events like proms, reunions and awards ceremonies most of these work fine. Not all of them work in true scale. When you shop for one of these programs, check to see that the program will give you a scaleable drawing that can be printed on tabloid paper without pixilation. Also check to see that the program will produce the drawing as a *.pdf file suitable for emailing. Finally, remember that at some point the drawing will be photocopied or transmitted by fax. Subtle gradations of color are lost in the translation. Important features should have sharp contrasts. Most of the programs will do this. For a comprehensive list of these programs visit Corbin Ball's site at http://www.corbinball.com/bookmarks/#p1 where he has twenty four entries of floor plan software.

From what you just read, you might get the impression that I think highly of these programs. It is true that most of them work as advertised. However, if you hang one item from the ceiling, you must step up to a real CADD program. Riggers require real CADD drawings.

Aerial Rigging has facility drawings at http://www.aerialrigging.com/hotel_cads.asp

There are other rigging companies that service other properties. The probability is very high that the best source of detailed accurate information on the main ballrooms is the rigging company. Check with your C S M to find out who rigs in their building and get your floor plans from them. The riggers will not have the plans for rooms with low ceilings or rooms where rigging is impossible, but for those rooms they do have the plans, use them. (Sidebar: Plaster ceilings are the bane of a tech's existence. We hate them for a variety of reasons not the least of which is acoustic echo.)

If you are not lighting your events or are flying your speakers, odds are you will never have to worry about riggers. For the rest of us, riggers are part of daily life. They require real drawings and real planning. Just remember, you can't hang the lighting truss through the chandelier.

So, on a twist from what the theme has been all week, if your event is large enough to involve a production company or a full service AV company, tell your production company or independent technical director you want them to do the floor plan drawings. You will have to pay for this, but it is money well spent. Tell them how many bars and buffets to put out. Give them all the information they ask for. Tell them you want the drawings in a real CADD program and you want them to submit the plans to the riggers. Once you have done all this, listen to them tell you how to best use the available space. They really do know how to set a room.


Tomorrow we wrap up with lighting and additionally a group of contacts who did not really fit anywhere else and are too important to ignore.


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