Spray Foam Application

Apply spray foam to fill the voids under the plywood sub-floor.

Insulating the floor of an RV is the least important as it’s less exposed to the elements. Because of interior height restrictions, I decided only to use Poly-Iso insulation between the floor ribs and fill the voids in between with spray foam. This will improve the insulation and add a little structural cohesion to the floor.

If you have a high roof van, an extra sheet of Poly-Iso would be a much better solution and you can still use the spray foam to ‘glue’ the sheets together.



Buy smaller bottles, unless you know what you’re doing. When you’re unfamiliar with the spray foam application, you may want to stop mid-way and re-evaluate the work. The spray nozzle then will clog up and the remaining content will be unusable.


This product has an expiration date; watch for it on the bottom of each bottle. It is a closed cell/waterproof foam, when cured; in this application, I will cut the excess off, which will make it susceptible to moisture.

Hold the bottle completely upside down when spraying and spray VERY slowly and always less than you think you need. It expands a bit when sprayed, yet will double in size after 5 minutes, when it gets its greatest expansion. It’s tack free after 15 min. and cured after 8 hrs. Spraying with water helps it to cure faster.

Don’t try to scrape it flat into other crevasses, when you just sprayed it. That doesn’t work, you’ll have to cut off the excess when cured. A good division of work is to spray in the morning and cut the foam with a hacksaw blade in the afternoon. Long strokes with the hacksaw blade worked best for me.

Which Parts To Choose

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Comprehensive Material List

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Great Stuff

Spray Foam
Gaps & Cracks
Cream color
12 oz


Blue Nitrile Disposable Gloves

3 Mil
Latex & Powder Free

Metal Hacksaw

3 Mil
Latex & Powder Free

Safety Goggles

Clear Lens
Anti Fog

3M Particulate Respirator

20 Pcs

Step-by-Step Application

Gather all the tools and materials before proceeding.

  1. Clean the floor of the vehicle.
  2. Shake well before each use !
  3. Install the plastic straw.
  4. Turn the bottle upside-down.
  5. The spray foam is applied to fill the low spots between the Poly-Iso panels.
  6. Spray VERY slowly and fill the outlines first.
  7. After a few minutes, when the foam is fully expanded, fill in the center.
  8. Optionally, spray a mist of water to speed up curing.
  9. After the foam has cured, cut off the excess with a hacksaw blade.
  10. Finally, clean the vehicle again.


  1. 2x 12oz Bottle Of Spray Foam ‘Great Stuff’
  2. 2x 16oz Bottle Of Spray Foam ‘Great Stuff’


  1. Hacksaw Blade
  2. Latex Gloves
  3. Water Spray Bottle
  4. Blower/Sweeper
  5. Dust Mask
  6. Safety Goggles


Very basic work that most of you can do. Use protective wear such as for breathing, eyes and hand protection.

The ‘Great Stuff’ spray foam used during this part of the project, was acquired locally and the total cost was about $18.91.


The missing parts of the complete van conversion process are being added regularly to this Build Guide. If you want to suggest a specific build option for this guide, submit a content correction or have a general inquiry, send me an email.

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Disclaimer: Throughout this guide, all guidance, building techniques and other information are based on my own experiences of converting a cargo van into a Tiny House on wheels. This guide is only for informational purposes; always build according to local and national standards. Be aware that such a project is expensive, requires a substantial amount of broad knowledge of building techniques and involves more work hours than you can imagine. Besides of hitting a finger with a hammer, much more serious harm can be done when you work with 12V/120V electrical systems, propane installations, power tools, etc. Tapping into the vehicle’s own systems can also damage its functionality. Get professional help where needed; never take any risk!