Building Your Own Spray Room -- On a Budget

Technical advice and alternatives for a small operator building a new shop. February 25, 2005

Our current shop is small (1000sft). We are designing a new shop, which we will be building in early spring. It will be around 2500-3000sft.

I have always sprayed in a partitioned area in our current shop with an explosion-proof exhaust fan. The shop is heated with a space heater. Other than the showroom area of the new building, the spray room is the one thing I want to concentrate on and do right. We spray pre-cat lacquers, alkyd stains and solvent dyes. I have no knowledge of spray booths, filter systems, air-makeup, etc. From what I have read, and having the luxury of starting from scratch, I am leaning toward radiant in-floor heating for the whole building. I tentatively plan to have the spray-room separated from the rest of the shop with a sliding door of some type. The actual spray area will be about 15x15 with an attached drying/flash-off room about 8x10.

First, can I still just exhaust with a proper fan and do I need a filter in front of it? Do I need to put a filtered opening in the sliding door separating the spray room from the shop (to replace the exhausted air). Will I need another source of heat to supply this air or will the room draw enough? I read a post in the archives that made mention of pressurizing the room to help eliminate dust. How does this work? Can I build a suitable spray room without having to purchase an expensive booth? We have operated in pretty primitive conditions until now and I want to do this right from the start in the new building, but don't have the budget to spend several thousand. I just don't have the knowledge of commercial spray booths to know how they operate. Keep in mind we're a small shop. What is your setup and what would you do if you were building from scratch?

Forum Responses
(Finishing Forum)
From contributor D:
First off, do you work in a city or county? Because if you're in the city, the first thing you need to do is pass a fire marshal inspection on any flammable storage and spraying. Go to them with your plan and see if it will fly with them.

Second, are you going to have to pass a local building inspection? If so, you have to run your idea past them to see if it will fly. Most likely, your insurance company is not going to insure you if these aren't done. You're not going to get someone off this site to tell you how to build a spray booth, because if you were to blow yourself to kingdom come, they would be liable. You could hire an architect experienced in this area to design you a room and go from there. But I think you will find it much easier and cheaper to buy a spray booth that is certified by OSHA.

If you switch to waterborne products, you can forget all the above and find out that it is much cheaper in the long run to go waterborne. I know they are a little more expensive to buy than pre-cats, but you will be safer and the environment will thank you, as well. Not to mention your insurance rates will be a lot less.

If you're flying under the radar and not pulling permits, I suggest educating yourself the best that you can and doing it safely.

From the original questioner:

Nope, not "flying under the radar" pertaining to permits. Honestly, there are no permits to get in my area (outside city limits) other than a building permit to cover electrical installation. I don't currently have any plans to speak of to take to any official. That's why I'm asking, so that I can develop some type of acceptable plan, and if I could afford to hire an architect I'd just buy a very nice commercial booth and have it installed. I have no interest in switching to WB finishes. I spray pre-cats, stains and solvent based dyes and even if switching to WB at some point were a possibility, I would not want to be limited to them exclusively.

I also am not trying to be unsafe. I am simply wondering what other setups are out there. I don't think it takes spending several thousand dollars on a commercially manufactured spray booth when I can accomplish an acceptable and safe environment with the proper equipment and setup. As to liability of someone telling me how to build a spray booth, that is like saying any advice that one gets from here puts the poster at risk of being sued. In that case, we'd all better be careful what we post.

So... can I still just exhaust with an explosion-proof fan with a filter media in front of it, and will I need a filtered intake in the door? Also, will I draw too much of my heat out and not be able to keep an acceptable temp with the radiant heating? Have some built acceptable spray rooms in their shops that aren't afraid to share their experience? As to the proper size fan, did I correctly read 100-150cfm per foot of exhaust filter?

From contributor R:
What you said will work fine. You will need some type of forced air heat when spraying in the winter. You need to draw warm air in your spray room. I don't think radiant will recover fast enough. You'll need a $600.00 explosion-proof fan mounted in the wall of the paint room. Filter your intake air from the heated and cooled shop, and open a window with a screen in it in your shop when spraying, as an air supply. As far as the filter from shop into spray room, a 25''x25'' AC return grill and filter would work fine. I wouldn't mention a spray room in the plans - just add it on after the final inspection has been signed off. The less they know, the better off you will be.

From the original questioner:
Thanks a lot. What kind of forced air heat would you suggest? Would you suggest another type of heat for the shop overall? Most feedback I've gotten about the radiant heat has been overwhelmingly positive, especially since I'm building from scratch. I had kind of toyed with the idea of putting a radiator of some sort in the drying room to provide some auxiliary heat there, to aid in keeping the drying room toasty. Reckon this would work?

From contributor M:
Put filters in front of your exhaust fan or you will be buying new fans after spending a good bit of your production time doing inadequate cleaning.

From contributor T:
I have a hot water radiator on the spray booth side of my air intake for supplemental heat in winter. Keeps it over 55 on the worst days while spraying. The flash-off/drying room is before the booth area, so that income air keeps it ventilated. The doors are well sealed and keep out all dust from the shop. Any dust already in the booth gets exhausted right away. My intake has a metal screen to filter out bugs, etc. I have 4 Spacemaster halon chemical sprinklers hanging from the ceiling. You can buy spray booth components to do it yourself. I spray WB mostly, but it is almost impossible to avoid solvent based finishes completely. The best stains and shellacs are explosive. Even oil-based paint can ignite. Use lots of heavy doubled-up drywall. In fact, get a copy of the fire code for booths from a city fire dept. You'll be safe for sure.

From contributor R:
I have two 5 KW electric units for heat, and a wall unit for AC. I just plug in the dehumidifier. The shop has 6'' walls with R19 insulation in them and same for attic. As far as the radiant heat, I have only heard good things about it. With TN weather, I can cut my heat off at night and in less than an hour, with both 5 KW units going, I can cut one off completely and the other back to medium, and as long as I keep the doors closed, I am okay until quitting time. However, when spraying, I run the two electric unit 5kw heaters wide open. A 2500 cfm fan will empty the warm air from a 2500 sq ft shop in 12 minutes if it has 12 ft ceilings. I try to spray at quitting time, regardless of season.

From the original questioner:
I have thought at times about a dehumidifier, but since I switched to the Magna lac and then MagnaMax a couple years ago, I don't really have that many blushing problems. That may change, though, as the new shop will be in a holler about 1/4 mile from a river and it gets pretty foggy there. What kind of dehumidifier do you use? Anyway, I kind of have a plan for my spray room now, thanks to all the info from you guys here. Now I just need to find a formula to size the fans. Some way to figure cfm needed to square foot of area. Thanks to all who have contributed thus far.

From contributor O:
In my area, worker's comp requires 50 lineal feet of air flow per minute per square foot of cross section of the booth. So a booth 8 feet wide by 8 feet high would require a 3200 cfm exhaust fan. A booth also must be able to contain a fire for a certain period of time - I forget the exact figure. Usually this means metal walls. I have seen people use steel studs and fireproof gyprock, but I don't know how up to code this practice is. Also, check auctions at bankrupt furniture factories. I saw a totally enclosed booth big enough to drive a car in and still have 3-4 feet all around go for $500 with explosion proof fan and lights. The only thing was you had 24 hours to dismantle and remove it.

From contributor Y:
I have been to a lot of auctions where the spray booth will not sell. Usually you can get it for almost free. Easier than reinventing the wheel. Take a couple of guys with you to dismantle it. You will understand how it works once you take it apart.

I think make-up air systems that heat fresh air are harder to get cheap, since the guys that have spray booths already are looking for them.

Hot water radiant heat? You could probably branch off the manifold and run copper tubing around a long intake duct to bring heated fresh air back into the spray booth.

Using the heat in the air you are exhausting to warm up the cold air you are bringing in will help keep your heat costs down, also. Run the exhaust vent inside the intake vent. The heat from the exhaust air will transfer to the cold coming in. This last Rube Goldberg part is off the top of my head, but it should work unless there are other problems I'm not aware of.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor G:
I recently built a 1,500 square foot shop with 10 foot ceilings. I put radiant floor heat in and I love it. The system circulates hot water through tubing in the concrete slab which is insulated. There are no drafts and everything, with exception of the valves, expansion tank and circulating pump take up a small place on my second floor. The water is heated with a tank-less water heater so I am not storing a tank full of hot water which serves no purpose. And since heat rises why not start the heat process in floor and let it rise naturally. I never have cold feet in the winter because the floor is warm.