What is an estimate of sq ft for each gender for a day spa lounge? Includes toilets, showers, steam room, lockers and lounge waiting area? Rotating use of 12 clients every hour.

Is 12, the total number of clients in the spa at any one time ? Or will there be 30 or 40, there with 12 coming and going each hour turnover.

And how nice and fancy are you going to be. Large steam room so there is room for growth ?

Will you be building new or using an existing building? If using an existing building, this will restrict the size of each area. It will also hamper growth.

Chuck

My first question would be fancy or not... I was a member of a gym with an enormous room for exercise and weights, but a small space for what you list, maybe 500 sq', and they probably had 150 people at a time.
If it's really a spa with mud baths and massage tables and so on, and you're not part of that, then a fancy shower/steam/toilet area for 12 I would say should be 800-900 sq' for each gender. Draw it on graph paper.
You have given us much too little detail to go on. I suspect that you know how many toilets and showers and so on. If not - then go ask.
You also have to know building codes where this is, for everything from width of doors to toilets and showers to the sizes required for handicap access. TONS to know.
I can't tell if you are a GC, a plumber, a designer, or what. If this is all you were given to work with, then you are dealing with someone with his or head in the clouds. Tell them to contact you when they can be more specific.

All the questions you asked are going to be STATE specific (if in USA) as well as dependent on local town/city requirements. Here, you need to contact the local building department in the area the spa will be and ask them for minimum requirements. Any guesses you get here (even if reasonable), no matter how much information you provide, will get trumped in the end by local inspectors and local board of health inspectors.

Save time/hassles and contact the local guys on this one...

Mark