I've had a hot tub for 4-5 years that I simply have not been using. The reason is that it's been too inconvenient to get to and use, especially during cold weather (when I would want to use it the most). I bought it used from a friend, it's probably 6 or 7 years old total. Has survived a few moves (installed at his place, moved to my place, finally moved to my current home). I'm in the process of planning for an addition off my house, and I'm considering building the hot tub into the room. The room will be 4 or 5 feet off the ground (on posts). I've spoken with a couple contractors, and the plan would be to build a slab underneath the room for the hot tub to rest on, and build the floor for the additional around the hot tub. The room will be unheated (maybe a wood burning stove), and very open feeling (lots of large screened windows). I have a 430 gallon Gulf Coast Spa (http://www.gulfcoastspas.com), model 10000-CR. Here are some of my questions - 1 - Any requirements for the interior walls? Contractors seem to think standard drywall is fine. I assume it is, since it works in the bathrooms, but wanted to be sure. 2 - Anyone have any similar rooms with a hot tub installed? Any special needs (ventilation, etc.)? I guess that's it for now. Thanks in advance for any help!

room size and ventilation is everything.

If you're talking about a room the size of your spa, with no ventilation when it's used on a moderate basis (2-3 times per week), you may be ok provided you use some serious primer and heavy duty paint on the walls. No cheap interior latex allowed.

Add power ventilation to that, then you can do whatever you want.

If the room is much bigger than the tub, and has reasonable usage and ventilation - (rest of the house because of open doors to the room or windows etc), then you should be able to do whatever you want.

Just remember you're dealing with an appliance that creates steam in a typical room temperature environment. Build and design accordingly - but there is no need to go overboard though, so depending upon your dimensions, size, and use habits you'll have to adjust on the fly.

Based on your explanation of the design though, the opinions you've received so far mirror my own.