I recently completed converting a 2000sf barn into a top notch mechanic shop, now I wish to add on to it and build a body shop with a paint booth. I am not talking about the home grown plastic type but a pretty professional type of spray booth that will last for years. These shops will not be for commercial use but only for my private restorations.. I am trying to decide how big of a building to add on which will depend on the size of the paint booth. What is a good workable size for a paint booth? 20x15? 25x15? 20x10? I was also thinking of buying a prefab metal building for the add on but am worried about the heat the metal would generate in the summer. Any advice on this would be appreciated

Paint booths can be purchased for a reasonable amount of money. When trying to piece meal them together you will often spend more money buying the individual components.

I suggest you look at the different types of booths, the CFM and filter requirements, the lighting, design (heated, baking, etc.) and the overall size. Build a structure that will house the booth and provide a clean area in front of the booth for masking and final cleaning.
Another thing to consider is a place for the finished car to sit undisturbed while it cures.

For the building I think I would go prepackaged steel pole building with an optional insulator kit. When we built my one steel pole building we installed a 6 inch thick pack insulation kit as the building steel was applied. Thing I like about steel pole buildings is you can quickly erect the building getting it in the dry, THEN, do your concrete floor in the dry so it cures properly. As for the booth, yeah, I'd go complete booth kit package. They are going to flow SAFELY and probably indeed cost less in the long run. Don't just look at new booth, consider used ones. You have to search, but they are out there. We had a large furniture spray booth go locally at auction. It was a 3 year old booth, complete and had 75 feet of quality ducting. Thing cost over $10,000 new. Sold for $1200 on a cold, wet, day in the industrial auction house. If I would have had the room for it I would have bought it.

Thanks for the advice.....I have been looking at complete package paint booths and noted the sizes. I think about a 30x50 add on will probably do and give space for the booth and working space for the prep. I just have to figure everything out first. It took me a year to convert the old pig barn.....I figure another year for the body shop. If it had not been for you fellas helping me on my first project...a corvette....I may never had done it. Below are some pics as to how it turned out...

Sweet! I'm jealous and trying hard not to be bitter. LOL