Spray Foam Application

Mod: Insulated Floor – Part Five

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.

Project Insulated Floor Content

Tie Downs & Wheel Wells
Paper Plywood Templates
Floor Insulation
Fasten Insulation With Glue
Spray Foam Application
Plywood Installation
Hardware & Soft-Ware

What You’ll Learn:

  • How to spray foam insulation.
  • How to cut spray foam to size.

What You’ll Use:

  • Hacksaw Blade.
  • Latex Gloves.
  • Water Spray Bottle.
  • Blower/Sweeper.
  • Dust Mask.
  • Safety Goggles.

What You’ll Need:

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

Approximate Duration For This Project: 3-1/2 hrs.


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.

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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.

Step-by-Step Application

Gather all the tools and materials before proceeding.

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

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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.

Other projects of this Van Conversion:

I’m just a DIY’er with a lot of common sense, but with some of the projects, I use some tools and materials, that require you to really know, what you’re doing. Always read the manual and consult an expert if you’re in doubt.

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  1. I like the way you did your floor. I don’t want to use plywood because it will take up space. What do you think about vinyl flooring on top?

    1. Hi Elle,
      I get it, especially if you have a Medium Roof van like I do. I already used a minimum amount of floor insulation and only 1/2 inch plywood. I don’t think, you can do with much less. Except for a one-piece vinyl flooring material, that is very sturdy, thick and resilient, I would not go that way. You will have to cover and walk on the floor ribs, which doesn’t give much support. If you want to use vinyl, do the plywood and some affordable vinyl. Under ideal circumstances p.e. High Roof, I would use 1+ inches of insulation and 3/4 inch plywood.
      Van Williams

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