Q&A Forums

Wide Open Roof Post New Topic | Post Reply

Author Comments
Posted: Nov 05, 2009 05:21 PM
Wide Open Roof
We have a Wide open roof (6500 squares) putting down 1 1/2" foam with a base coat of silicone using a Gama 250H.

How many square feet do you guys think can be covered under normal circumstances with an 03 or 04 tip?

This Gama 250 Rocks, but since we have architects on the job that require we base coat what we spray during the same day, I don't want to get to far ahead of my coating guys.

What are your thoughts on spraying? At 40 Pounds a minute, a set can easily go within an hour of spraying? With my Graco GH833, I am not sure if we can base coat more than 5000 sq. ft a day without help or adding a second coating rig!
Dennis Davidson
Posted: Nov 06, 2009 08:51 AM
Hey Steve

Good to hear you got a nice one!
The G-250 IS a great machine! On a wide open roof you should be able to comfortably put out 5-7 sets per day and much more on a good day. As far as the coating goes, your 833 should have no problem keeping up. If your only able to put on 5,000 sq ft of coating in a day something need to change. I've sprayed out 15,000 sq ft of urethane in a day working alone. You could put a second spray line on that 833 and do almost twice as much. Get a high pressure "T" and put it on the pump outlet and attach two coating lines. Use two 31 tips and it should do fine. Your 833 is a high volume machine, I bet under the right conditions you could even put three lines on it.
I use to help spray foam in the morning and after a few hours start coating. By the end of the day I would almost catch up to the foam guys. If your set-up right you should be able to empty a drum of coating in about 45mins or less.
If I wasn't so busy up here right now I would come down and help out.
A few questions:
What size is your spray hose?
How long is the spray hose?
What size tips are you using?
What gun are you using?
Transfer Pump size?
Transfer hose size?
How long is the transfer hose?
Are you mixing the material?
What is the material temp?
Posted: Nov 06, 2009 09:10 PM
Hi Dennis

We have been doing under 5000 sq ft roofs for the last month, so I didn't use your suggestions yet.

I am planning on going to a 3/4" hose for the first 100 ft then 1/2" for the last 50 and a 3/8" for the whip.

I would love to be able to add a second hose and spray gun to the rig, but I didn't think that I the 833 could handle two rigs spraying silicone.

I am still using the suction pump on the Graco and am ready to get a transfer pump to help out.

What transfer pump should I go with and what size air compressor do I need (How many cfm)to run the transfer pump?

Yes, nice roof! Its good to finally get to do a larger job that I don't actually own the property. We have been doing anywhere from 30 to 150 square jobs all summer, so it is nice to get a bigger job for a change. God knows we put our time in to finally be moving up the ladder.

Ah, what is a 31 tip? Is it a 631? And we are not mixing. Should we be? Should we use a regular Air driven agitator or something better?

Thanks for the help!


PS I will come up for the summer for a free week of work just for the experience. I am not as young as I once was, but still young enough to spray all day....LOL
Dennis Davidson
Posted: Nov 07, 2009 05:07 PM
I feel your pains. I'm not so young any more either! But I can still spray the heck out of coatings. My personal best is 13 1/2 drums in 4 hours (acrylic). I designed and build a special high production rig for a big project years ago.

How is your spray pattern? Does it spray with a bunch of streams? Does the pattern fluctuate? How much coating are you putting on at one time?

I'm assuming your 833 is not equipped with the direct immersion kit where the front end can raise up and the pick-up tube can then be lowered into the drum. That being said I'll move on.
1. Transfer Pump - Graco "Monark" 5:1 minimum! Mod. no. 218-956 About $2,000.00
2. Transfer Hose - I use Parker 422/421-16. This is a 1" ID hose, 20' long. You could go with Parker 451 TC 12 This is a 3/4" ID with a Tough Cover on it. Either should be under $200.00
3. Air Compressor - The book says 8cfm for the 5:1. I'd go a little bigger. If you can use the facilities air supply it's all the better, even if you have to use 200' of air line. (done it)
4. Mixer - Air motor driven is safest.
5. Material - If your coating isn't 70+ degs. you need to either warm it up or thin it down. (80-85 degs is ideal) You can thin it down with upto 5% solvent. Check with your supplier for the proper thinner. I think most if not all silicone can be thinned using mineral spirits.
6. Tip Size - 31 = 531 or 631 If not to windy use 631. It's not only wider, it atomizes the coating a little better than the 531
7. Pressure Hose Size - I think you got this one handled. Again, the Parker 451 TC hose works great for roof work. Nice tough covering.

Your 833 should be able to handle a second line. Providing your getting enough pressure at the gun. Hose restrictions, cold material, thick material and pump starvation can drastically effect the gun pressure.
Gerry Wagoner
Posted: Nov 08, 2009 06:29 PM
Sounds about right. 631 is our tip of choice for silicone.
543 for large acrylic roofs.

I'd go with an 04 tip and let er rip. (rhymes). Monark is a winner - we got 4 of them.

have fun,

Dennis Davidson
Posted: Nov 09, 2009 08:30 AM

After thinking about your problem I realized I'd forgotten to ask you one very important question. Do you have any filters in your coating rig or spray gun? This may seem like a dumb question but it's more important than you might think. The filters in a spray rig are designed for paints not coatings. The use of a filter will reduce the ability of the spray rig to maintain pressure and volume when spraying coatings. I just had this happen with a contractor in Iowa. He called and asked us for help because he couldn't get any production out of his new 65:1 coating pump. We went there, removed the filters and sprayed more coating that day than he had all week.
I know your 833 is big enough to handle two lines and just wonder if this might be the problem.

BTW The purchase of a G-250...Good decision! If you need any parts, hoses, etc. I know where you can get it cheap.
Posted: Nov 30, 2009 04:39 PM
Hi Dennis

Rebuilt the pump on the GH833(Washers, o-rings, balls, etc...) with a rebuild kit from Graco Friday before we left on a 15,000 sq. ft roof.

Pump performed great and kept up with me spraying about a set an hour (03 Spray Chamber, they forgot to include my 04 with the new fusion).

This is the second time that all my problems were solved by simply getting a rebuild kit.

I don't think that I will overlook that again. Now, I am excited to think what will happen if I go to a 3/4" hose with a feed pump on the front end.

I may not be able to keep up with my guys then...LOL

PS I like the new Gama. Far cry from an E-20
Dennis Davidson
Posted: Dec 01, 2009 10:33 AM
Glad your equipment is working better. Your GH833 is a high production coating pump and is more than capable of keeping up with one foamer.
With the size of roof your on and being wide open, have you thought about getting a robotic applicator? I know a contractor that bought one and it payed for itself in material and labor savings on their first job.
Posted: Dec 01, 2009 01:57 PM
but for now I will be just happy paying for myself.

Maybe one day!


You need to login to reply to this topic. Please click here to login.