This was posted on Trainboard awhile back, but I want to also post it here for anyone looking to build a paint booth...
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I've had a couple of requests for info on the paint booth I built for myself. So, here goes. First....
***DISCLAIMER***
This booth is for use with water based paints only! DO NOT USE SOLVENTS!! Things, possibly including you, may go boom. Very bad. Also, there is some 120 volt wiring involved. If you do not like this, don't try it. Ask someone who can to do it for you. Use these plans and instructions at your own risk. Blogspot and myself take no responsibility!
*** END DISCLAIMER ***
Okay, first the plan...
Although I used 1/4" Luann plywood for construction, you can use something else. I would suggest 1/2" for the base and back, maybe even the top. Luckly, pretty much every Home Depot and Lowes carries 2'x4' sheets of ply that will fit in just about any car so you can get it home. You'll need 2 sheets.
Second, you'll need the fan. I used a NuTone Basic bathroom fan, model 695, Home Depot # 127-767 for $29.93. This is not a sealed unit, so no solvent paints in it. I've had no problems with PollyScale and Modelflex paints. It's a little loud, but not bad. You can get quieter fans for more $$$. That's up to you.
Third, you'll need some 1/2" and 1" square wood for bracing and to hold the filter. Either rip you own, or you can get small hardwood in most of the Millworks sections of the big box stores.
You'll also need a filter (10"x20"), cheap electrical cord, dryer ducting (flexible is better), duct tape, some small metal tabs to hold the filter, nails, some bolts, nuts and glue.
So here's the cool part. You can build this wider or smaller if you want. But basically, we want a box shape. The recessed top can have a small, under counter light added to it. Cut the plywood to size. the base and back are 18" x 24", the sides 18" square before you trim them. Cut the hole in the back for the fan, leaving enough room for the base and the filter supports. The top is scrap. Attach the square stock to the base sides and back with glue and finishing nails, flush with the edge. Attach the sides and back when dry, then add square stock to the corners for bracing. Also add bracing for the top as well. You can add the stock for the filter. Just lay the filter inside and cut the wood to fit. Attach the tabs to hold the filter.
Now to wire the fan. Instructions are included with the unit. I used a common extention cord and cut off the outlet end and wired that in. You can use wire nuts, but I prefer to solder and tape up the connections to insure they stay connected. Test the fan, then place on the back and mark for the mounting holes. Depending on the wood you use, you'll need screws, nuts and washers to hold it in place. Once mounted, run duct tape around the edges to seal it up good.
Place the filter in the booth and lock it down. Attach the dryer vent tube and get it pointing out or hooked up to an outside vent and plug in the fan. You should find good airflow towards the back. You can add, as an option, the carbon filter MicroMark sells for thier booths which should fit. This will help with more filtering. I swap out my filter when it gets clogged up after awhile.
The base mine sits on was made of 1x4's with some plywood shelves. Lots of storage under there! I added a utility strip to the side with a switch to turn on my compressor and fan. The light is seprate. A lazy susan makes it pretty much complete. You could get a couple of plastic tubs to hold the paint for under the booth.
Have fun!
So here's the cool part. You can build this wider or smaller if you want. But basically, we want a box shape. The recessed top can have a small, under counter light added to it. Cut the plywood to size. the base and back are 18" x 24", the sides 18" square before you trim them. Cut the hole in the back for the fan, leaving enough room for the base and the filter supports. The top is scrap. Attach the square stock to the base sides and back with glue and finishing nails, flush with the edge. Attach the sides and back when dry, then add square stock to the corners for bracing. Also add bracing for the top as well. You can add the stock for the filter. Just lay the filter inside and cut the wood to fit. Attach the tabs to hold the filter. 
Now to wire the fan. Instructions are included with the unit. I used a common extention cord and cut off the outlet end and wired that in. You can use wire nuts, but I prefer to solder and tape up the connections to insure they stay connected. Test the fan, then place on the back and mark for the mounting holes. Depending on the wood you use, you'll need screws, nuts and washers to hold it in place. Once mounted, run duct tape around the edges to seal it up good. 
