I am building a 30'x40' shop and plan to build a paint booth in one side of it. I've attached a quick sketch I did in paint to show want I was planning to do. I've never actaully painted in a professional spray booth so my knowledge is limited and I could really use some input. Basically what I am planning is to have a pit with a grate over it running down the center of the booth. Then have 3 pieces of PVC pipe to route air to run out of the pit to a fan box outside the shop. It will be a negative pressure booth with the air inlet coming from filters in the ceiling. The pit will have a drain in it to drain water for when I wash out the booth. Lights will be recessed into the walls and the aircompressor will be in a separate room behind the booth.

Questions:

I don't know if the 3 pieces of PVC will provide good even flow down and out of the booth.
How big should my PVC be? I was thinking about using 10 inch.
Is this the best route to take in building a booth, downdraft I mean? I work in construction so building it is the easy part and will surely save me some money versus buying one.


I will have a backhoe digging the the footing for the house tomorrow and was planning to dig the pit for the paint booth as well as bury the pvc while I was at it.

Before you get ahead of yourself and spend a bunch of money I recommend you do a bunch of reading first.
Proper airflow control is crucial to having a booth that will keep dust and over spray under control.
The intake/exhaust filter banks must be sized properly based on the volume of air necessary to keep the flow rate at an acceptable level. Also if there are flow obstructions the air will tend to recirculate in the booth actually adding to your dust problems.

Do a search on here for Homemade Paint Booth.
Also I have an article that you might find if you google: principles_of_ downdraft_booth_technology
If you can find it let me know and I'll try to get you a copy.

Also, consider buying a used cross-draft booth. That way someone else has done all the R&D for you. I've seen them even on craigslist sometimes for a couple thousand dollars.