In this article, we’ll cover what to consider when choosing a spray foam rig. The details of these considerations are extremely important. If your rig is not built to industry standards, you could have issues down the road and lose your costly investment far too soon.

The rig that carries your equipment is just as important as the equipment inside. After all, if you can’t get to the job, it doesn’t matter what you’re carrying! Use this resource to stay up to date on SPF rig and trailer best practices when it comes to designing your own rig or investing in a pre-built one.

SPF Trailer, Rig Weight and Capacity

Spray Foam Rig Weight

How is the trailer constructed? Is it built to withstand the weight of heavy equipment and drums of material over time? The trailer you use should be built for a spray foam contractor. Trailers that are reused from other applications likely don’t have the capacity to carry the weight of your spray foam equipment.

Knowing your spray foam rig load strength is critical as the interior components of a spray foam rig are very heavy. Because of the ring it sits on, the 500 lb. drum’s weight puts pressure on only a few inches of your rig’s floor. Trailers that are not built to SPF specs can eventually have sagging floors, or even worse, drums and equipment that end up falling through the floor.

Here’s a thought, a fully loaded 20’ tag-along trailer, without foam, can weigh over 9,000 lb. If you add two sets of foam then your rig will be carrying 13,000 lb. A typical 20’ tag-along is rated for 14,000 lb. This leaves 1,000 lb. of wiggle room for ladders, scaffolding or even a third set of foam. Let’s look at some number estimates (this estimation does not include the weight of spray foam insulation itself, which can vary throughout the day).

The Weight of Basic Spray Foam Rig Components

  • 20’ Tag-along trailer: 4,100 lb.
  • Diesel generator: 1,500–2,100 lb.
  • Compressor: 700 lb.
  • Proportioner, hose, guns: 500 lb.
  • Aux equip. (heater, AC, air dryer), electrical, plumbing, insulation, hardware (barrel braces, hose hanger): 900 lb.
  • Toolbox, bench vice, wire wheel, tools, breathing air: 500 lb.

Contact your local IDI if you’re unsure how securely your rig is holding the weight of your equipment and components. We host IDIREV rig evaluation events to help you manage these issues and any others that may arise.

As always, we recommend you follow all local and federal recommendations for weight distribution.

Spray Foam Rig Towing Capacity Questions to Consider

What is the cargo capacity of your rig? What is the Gross Vehicle Weight Rating (GVWR)? Can the trailer support two or three sets of material, as well as a generator, compressor, and one or two proportioners?

When considering an SPF rig, you need to take the towing capacity into account. This consideration is important and yet is one that’s often missed by suppliers who aren’t experts. If your trailer is not designed to the correct weight capacity, you can have issues with your axles bending or even breaking.


What is the interior height?

Ample headroom makes it easier to change out a transfer pump without tilting the material drums. A lack of interior height can be very dangerous for your installers. Tipping the drums to get pumps in and out of the barrels can easily break or take off fingers.

What are the interior finishes?

You’ll also want to consider how the floor of the spray rig is finished. Spilled chemicals, sliding barrels and even foot traffic will wear heavily on a floor that isn’t built with durability in mind. Over time, this can cause the floor to rot. Without proper paneling on floors and walls, spilled chemicals can absorb off-gas and promote harmful VOCs in your rig. To promote longevity, walls should be thoroughly painted at a minimum, at best the walls should be paneled with a faced sheathing. Paneling limits VOCs by maintaining cleanliness.

How is the temperature in your rig regulated?

Is the spray rig insulated? Does it have an air conditioner and heater?

Maintaining the chemical temperature is important to better control the reaction between A and B materials, resulting in better material yields and more ROI after every project.

In warm weather, an air conditioner helps prevent material from overheating and expanding drums and keeps humidity at acceptable levels. In cold weather, a heater makes it easier to warm up materials to optimal spray temperatures. Your rig should have the ability to process foam according to the manufacturer’s recommendations no matter the conditions of your climate!

Money-saving SPF Rig Temperature Tips

  • Most climates in the US will fall under 45 degrees and rise over 95 degrees throughout the year. Both ends of this spectrum are problematic when processing SPF.
  • Insulate your trailer: If it’s not fully insulated, it doesn’t matter much what mechanicals you’re using; the foam will be damaged by harsh climates.
  • If we believe SPF is a premium insulator, shouldn’t we start by installing it in our own rig to keep the interior temperature regulated? Some rig builders overlook this in an effort to reduce the price. Practice what you preach!


Choosing a trailer equipped for proper weight-load distribution is vital. Proper weight load distribution keeps tongue weight at an acceptable level, promotes safe towing conditions and prevents swaying.

Pro tip: It’s smart to keep tongue weight between 9%–15% of the loaded weight of the trailer. Trailers pull much differently when fully loaded (to the job) and empty (from the job). A properly balanced trailer will pull safely both ways.

The weight disparity issue is more prevalent in a tag-along trailer. The reason is the weight rating of a receiver hitch vs. the weight distribution of a gooseneck. This problem is solved by placing the axles in the correct position on a tag-along trailer.

This is one of the reasons why just any trailer won’t do when building a rig. We work closely with our vendors to make sure the trailers are ordered with the axles mounted in the correct position, meaning there’s a specific measurement from the tip to where the axles are mounted. That way, we are under the 15% rule when loaded going to the job, and over 9% when empty coming home from the job.

Consider Looking at the Label on Your Pickup’s Receiver Hitch

Even a Class 5 hitch on a 1-ton dually is usually under 2,000 lb. A truck that isn’t a dually will have closer to a 1,400–1,600 lb towing capacity. Now let’s consider the spray foam rig capacity requirements. On an SPF rig diesel generator alone can exceed this weight limit, not to mention the trailer weight itself or other equipment placed over the tongue.

Many SPF professionals say, “We put the drums over the axles so it balances out”. That’s fine if your rig is sitting in your shop! Most of us don’t want that. The weight of spray foam insulation chemicals isn’t fixed! When we’re busy, our rig can fluctuate by 3,000 lb. on any given day, whether we’re fully loaded or empty on our way home from a job.

Insulation Equipment Housing and Installation Within the SPF Rig

Where is your equipment located in the rig? Is it somewhere where drums will consistently hit your proportioner and eventually cause damage to your machine? You and your crew must make sure your hoses are out of the way and on a hose rack (built specifically for spray foam hoses) so they don’t get snagged as well.

You also need to make sure your rig is plumbed and all electrical is run by a certified electrician. This is very important because if someone is wiring your SPF rig or trailer and they don’t know what they’re doing, they can fry your machine!

Considering an SPF Rig but Unsure How to Get Started?

In short, make sure your rig builder is someone you trust and are completely comfortable with. This is a lifelong investment, and cutting corners usually ends up costing you more money in the long run. Working with the pros is crucial.

By: Ken Allison, Director of Business Development

Ken specializes in business development and building science. You can find him at any of our training events around the country helping local contractors grow their business. Contact your local rep about the next training event near you to hear Ken’s advice first-hand.

Read the Full Series:

Read our full rig series to determine what type of rig you should invest in to get the most ROI. Learn about the important factors that should go into your rig purchase decision — and how they could affect your rig’s performance on the job … and your profitability!

  1. Introducing Our Mini-Series (what you should know about owning a spray foam rig)
  2. How to Choose the Right Air Filtration System
  3. Air Pressure & Volume — Is Your Equipment Sized for Optimal Performance?
  4. Choosing SPF Equipment With the Best ROI
  5. Choosing Power and Auxiliary Equipment
  6. Other Cost-Saving Considerations


Have a question on anything insulation, pricing, or want to place an order? With hundreds of products and countless services, our experts will help walk you through the process of getting ready for your next project. Get in contact with our team today for help and guidance on the right products and best techniques for you and your business.