Hey all! A little background first before the questions, I've been wrenching / building old cars, drivetrain swaps, etc for the last 16 years now. I love new challenges, but body and paint have always been my weakest point, I don't know if I just don't have the eye for it or if I need to practice more, but my first attempt at body work was horrible, mostly I kept burning through the bondo spots and just felt way in over my head. From my first attempt in an apartment garage...9 years ago maybe


Ended up sending that car off in the picture to a guy that was supposed to spray it on the side, but instead left it out in a field in bare metal and with the t-tops off, for months, and by the time I got it back (he never touched it) I was so pissed off about the situation that I had no further interest in the car. That coupled with other unsatisfactory body and paint results led me back here to face my enemy.


I've been reading and researching over the past two months now trying to figure out how to setup the spray booth I'm building in my backyard. Even though I've come a long way from my "just need to build a room with lights and a fan" assumption, I'm still working on a gameplan. I have a 20x21 shop I'm working on building next to my main garage (the barn) roughly 80 feet away from my house and nowhere near any others. I plan on making this a positive pressure booth since there's a lot of dust floating around out here and I'm in somewhat of a windy area. Ok, so here's where I'm at so far with the booth



(Compressor will go in the space between main shop and spray booth)

...and onto the questions!

-- The most pressing one right now (because I need to know this before construction can be resumed) is if there's a calculation I can do to find the square footage that the intake side should be? Basically my booth cfm requirements are about the same as coronet's (almost 12,000 for a 3/min air exchange), so I figured if all else failed I could just use his current intake size and go from there.

-- I'm considering using a sliding wooden door for the center entrance, but that would have me put the exhaust filters into the sides of the building. I'm assuming this isn't recommended because almost every paint booth I've been looking at keeps the exhaust more focused towards the center. Is this to help keep airflow away from the walls? If not the sliding wooden door, I'm considering to just install a metal rollup door and raise it on top of filters when I'm spraying, which is what I see most people doing (and coronet's awesome booth is usually the first to pop in my mind when thinking of this). Which would be a better option of the two?

-- As I mentioned earlier it's about 10-15 mph on a typical day where I'm at, towards the top of a hill with not much tree coverage. Would this play a factor in the airflow dynamics of the booth if that wind is blowing into the exhaust filters while I'm trying to spray?

-- How many of you are running explosion-proof lighting? I have access to some really bright / reflective fluorescent lighting, but they're open to the elements. I thought about building cabinets and sealing them off in plexiglass, but then I look at so many other booths and don't see anyone else going through the same trouble. Coronet if I'm not mistaken, I believe even your lights are open in the booth. Is this something that if airflow is good enough through the booth, it shouldn't be an issue? I'm also considering using LVLP to cut down on overspray.

-- Without having to resort to using plastic sheets, is there a preferred material that I should use for the walls that's easy to clean and isn't as prone to trapping particles as something textured is?

-- I'm considering making a boxed housing for the intake side, similar to coronet's, but running some ducting into the inside of the main shop where I can have a heater cranked up during the winter, that way the spray booth could be heated without risk of fire. If I insulate the booth instead, would that eliminate this need?



My apologies for the long post, I just want to make sure I do it right the first time, or at least get it close enough that it's easy to tweak in the future lol. Also if anyone has any other suggestions feel free, I'm all ears. Thanks!

Take a look at this single post: viewtopic.php?p=132408#p132408

It talks about balancing the air turnover with air velocity and CFM. Unfortunately the rest of that thread has some bad information so you have to sort of skip over that.

On the lighting, I would see about LEDs. I recently converted all my garage 4' tube fixtures over to LED and they are very bright. You can get a color temp close to natural sunlight. I have not checked but it would be interesting to know if they are explosion resistant.

By the time you get it all done and put up fans lighting your going to be into it deep.
Can it be done cheap ya will it work? who knows ? designing a paint booth that functions correctly is questionable at best. You can buy a real all steel unit with correct fans and lights economically thats the direction I would go, you can get into a cross flow for $7200.
http://www.autobodytoolmart.com/col-met ... 12556.aspx
or a semi down draft for $8200
http://www.autobodytoolmart.com/col-met ... 12557.aspx

Plus you can finance it by the time you get done building what ever you dream up thinking what is right you more than likely gonna have an expensive wind tunnel you cant paint in in certain areas as the air flow pushes your Guns paint spray pattern around.

Dont forget too that a real paint both will come with Safety switches that shut the fans off when doors are open a fire detection and suppression system if added and a real manometer.

Even if you only do a few paint jobs with it you can always tear it down and sell it easily.
Hard to beat a real Booth with prices like that

I agree with Dennis.
All the time and money I spent for materials, lights, fans, filters for my booth could have easily purchased a professionally built one.
The problem I see with your design is the turbulence that will be created. The positive pressure aspect is good in my opinion for the very reasons you stated. However, you will need exhaust fans to prevent the turbulence (something I am still fighting with) created by trying to force air into the booth and out the exhaust filters.
By its very design the booth is relying on exhaust CFM being slightly less than the intake CFM so not all the air coming in is going directly out. This creates a tendency for the air to swirl back into the corners next to the intake filters.
I believe the only way to remedy this is to have exhaust fans pulling the air out at a rate just slightly less than the rate of the incoming air. They will need to be almost identical but not quite.

My advice is to turn your planned booth into a building meant to house a professionally made booth. I would make it long enough to have a car parked in front of the booth for masking and prep purposes and wide enough to have sufficient space along the sides and back for easy access to the exterior of the booth and for shelving and cabinets. You will need painting and masking material storage, racks for holding doors and fenders, as well as places to store spray guns and other equipment.

I got mine used off of Craig list guy was asking 4000 I got it all disassembled for a song he had had other people come and look at the pile of metal and all had walked away I pilled it all on my tailorfor $1500 is one for $5000 used all taken apart too!

http://inlandempire.craigslist.org/hvo/5908153792.html

Here is another for $14.5K
http://lasvegas.craigslist.org/wto/5916330904.html
But he includes a $3000-4000+ Air drier, A $3000-4000+ Air compressor and a $4000+ Halon Fire suppression system. Cant say the booth is worth more than 5k though in my book I would give him 6-7 tops for all of it as long as the compressor is at least 7.5 hp looks like a 10 hp and if the dryer was at least rated at 35 CFM unit.

Guys starting out don't think about these other necessary pieces of equipment, You absolutely need at least a 7.5 hp Air compressor 30-35 CFM min and then The Air drier that's a Must too Ya you can get away with filters and desiccant (Dehumidifier filter) but a real Drier is the way to go for clean dry air. And A good Fire Suppression system is Just Priceless when you need it.

Thank you all for your suggestions so far, though I wasn't expecting them to be that depressing, lol. Guess the truth hurts. Coronet, I'm surprised you'd still rather go with a professional spray booth over what you have now, because from what I remember you got yours built pretty cheaply. If I just need to add fans with the exhaust filters, that doesn't seem like it should be much more of an obstacle. However, (from what I gather) it sounds like the turbulence is strictly an inherent design flaw of a positive pressure booth...so if I change design around for a negative one, would that eliminate the turbulence problem? I'd just need to make sure that everything is tightly sealed off. I have a larger barn next to the spray booth that I can use to keep paint supplies.

Few things I'd like to add; since I created this post, a bit more work has been done to the construction of the paint booth, so I'd really hate to just abandon the plans for it. WORST CASE I can make it a body work only booth, then take it to a separate spot to spray it...but I'd prefer not to go that route as it seems like a waste of space. I've also seen some pretty good paint jobs come from a garage (which is probably one of my biggest motivators for me to keep pushing with this booth), without any fans or filtration setups whatsoever, so maybe I'd be better off not trying to mess with airflow for my first few paint projects. Which brings up my third point, and an important one, I've never painted an entire car before, and though I intend on practicing to get better at it and one day be proud of something I painted, I could completely suck at this and the booth would be a bunch of wasted effort. For that reason alone it's difficult for me to consider over $5k for any type of paint booth, used or new. I'd like to see if I can get the hang of it first before deciding if it's worth the investment.

I'm not trying to dismiss any of your concerns at all, and I really appreciate all of your input for it is far more valuable than my inexperienced assumptions. But I already am invested in this makeshift spray booth, and would rather figure out a way for it to work than abandon it.

Turbulence can be in any style booth.
I have a .pdf document called The Principles of Down Draft Techology by Rick Farnan. He teaches seminars for AkzoNobel.

Send me a pm with your email address and I'll send you a copy.

I just got done reading this thread, I have never used a positive booth. Every booth I have used has been a negative force booth and that has been quite a few different booths. Some have been homemade and some manufactured cross draft booths. The booth at my first job was homemade with two 5 ft X 7 ft doors totally filled with furnace filters. There was a small fan toward the front on the side wall. This booth put out the cleanest paint jobs I've seen in all the years I've been doing body and paint work. At the risk of really dating myself the paint used back then was synthol enamel, not exactly a easy paint to get dirt free paint jobs. As a disclaimer I didn't make my living as a body and paint man but I worked 20-30 hrs a week in a body shop somewhere for most of my adult life. Now I'm retired and work at my pleasure on my 66 f100.. Oh yeah, in my opinion a paint booth should be used for one thing and one thing only-- to paint in. I've seen too many booths used for everything and then wonder why they can't get a clean paint job out of it.
Grump

ZEEBOOST
I didnt mean to come down on ya like it was impossible you can build one that will work and work well But You need to forget what you think a Paint booth is and how it works because you got it all wrong your picture with drawn in intake and exhaust filter area says that.

Both Intake and Exhaust must have exact same dimensions and square footage of filter area.
Now those are big areas to deal with Now you need each panel to act as a single filter with equal airflow across whole area. That means ALL the Intake filters work as one and ALL the time, The same for the Exhaust filters they must work and act as one together even when they are Two different panels on o posit walls apart This is not easy to do It requires the use of Large Air boxes and Plenums in some cases.

I suggest looking at Real paint booths for a while and study there use of Air boxes to spread Airflow out across the entire Filter area. It really doesn't Matter if you make the Booth Positive or Negative Pressure they key is to have equal flow of air across all the filters at the same time.
The Bigger the filter area the slower the Air will travel through the booth the Smaller the filter area the faster the air will travel through and cause turbulence. Then you have to contend with Dead air or Trapped air in areas of the booth. The Trick is too design in as few as possible because You don't want to bring in extra fans to compound problems.

I suggest copying a Full Draw through design or a Semi down draft design, Both work well and have been built and designed by many companeys for many years just don't use to big or too small of a fan. and do not De-leat the use of Air-boxes.
Balanced air flow is the Key to making it all work.
This may may be a little to complicated for ya but you should give it a once over any way
http://www.google.co.uk/patents/US6226568

In Both of these designs below they do not show clearly the use of 20"x 20" Air filters 20 intake and 20 exhaust. And The details of the exhaust air-box is not explained either. But they dont have to they are in the business of selling units not telling you how to build a home made fire trap. If you stray to much from one of these designs expect some turbulence, dead spots or wind tunnel effect in your booth. There are reasons these two designs have been around for so long and why the same design is built by so many different manufactures....... think about it.

https://www.paint-booths.com/product/CF-1000.html

https://www.paint-booths.com/product/SD-1000.html

This Picture shows the Modified Air box I have on My Paint Booth this encapsulates all the exhaust filters so that they all work and flow the same as if they were just one filter. Note the Manometer on the Box aft of the Dart board.

If I could add One other bit of advice to building a Custom Paint booth it would be to Double the Amount of lights used!

And Again here is another fully disassembled ready to ship cheap
http://inlandempire.craigslist.org/hvo/5908957363.html
He wants $5k bet he would take less! hes in Southern CA, By the time you get done with Lights fan safety equipment wiring its hard to beat a good pre designed booth. Especially when It can and will pay for itself the first time you use it.