Building a small drum room. Need help.

So, I'm in the process of putting together some plans to build a small drum room in my studio. Right now I am only able to do overdubs and such, but figured it would be nice to be able to do everything, so I'm adding onto the concrete slab on the side of my garage. The dimensions for 16.5' x 18'. I was planning on 8 foot ceilings. I wanted to soundproof it like I did my mixing/overdub room since I have neighbors next door. I only plan on tracking drums during the day, but I wanted to be safe about it. I wanted to see if you guys could give me some insight on maybe how to design the inside. I know some different angles would be better than making the room a complete square/rectangle. I'd also like to know what would be the best materials to use if my budget is roughly 10k. I was planning on not covering the concrete and just leaving that part of it exposed. I'd like to know if that is a bad idea or not. I now realize that after building my overdub/mixing room, if I would have come here first and asked these same questions I might have a better sounding room. Here is what I am working with. I would appreciate any feedback. Thanks. http://img233.imageshack.us/img233/2102/studio2lf.th.png

I also wanted to see if you were to redo the whole space, what would you do with it? I am contemplating a whole new plan, since the placement of the mixing desk and the size/shape of the room isn't really ideal. I sure wish I knew about this place when I built my mixing/overdub room. I'm learning so much just going through the posts. Thanks guys.

did I maybe not mention enough details? I tried to be very direct, but maybe I am missing something? I'd appreciate help on this. Thanks.

are your measurements correct as your drawing isn't to scale. here is a layout to scale as close as I can figure given the measurements you supplied. cheers john

John, Thanks a bunch for the illustration. Sorry, my skills are low with that, but those are actual measurements. I haven't build the drum room yet, but that is the size of the concrete slab next to the garage. All I have to do is knock out the wall where it says "door? glass sliding" to begin. Now that you know that those are exact measurements, can you tell me approximately measurements those angles are that you are recommending? Also, since I have neighbors, do you think I would be ok with insulation or owens corning 703 or would I need to build a room within a room sort of thing? What about the concrete floor? Would I be better off with a raised floor? On that darker corner on the top right, would I be filling that up with insulation or an extra wall? Sorry, very new to this and here... I'm just trying to gather as much info reading the site and asking questions before I turn it over to the contractor doing the work. Thanks again John.