Insulating a Van Floor in a Chevy Express Van

Chevy express camper van floor insulation

How do you prepare and insulate the floor of a van to convert it into a campervan or home on wheels? To be honest, I didn’t think this question was going to take me so long to answer. It may not take you as long to answer – a lot depends on your goals, preferences, and your van. It also depends on how many steps ahead you’re planning at any given moment. I looked at over a dozen different versions of floor insulation before making my decisions, so here’s my contribution to the body of knowledge out there: what I did and why I did it.

Planning Ahead

It’s ideal to have basically your whole design figured out before you actually build anything…and yet, we don’t live in an ideal world. What the heck, right? In my research on how to insulate a van floor I found many references to how helpful it is to plan ahead for where your electrical system wires will run and where you might drill a hole through the floor for the water or heating system. That did sound helpful, but also not necessarily feasible. I started out on many an internet journey to answer one specific question, and two hours later would have 12 open tabs on five different subjects that taught me a lot but didn’t solve my original question. Lots of information — but no answers.

It seems like at this point in van build out world, “correct answers” are nearly impossible to come by. In some cases they just don’t exist yet. So for one thing, I had to give up on that idea to really get anywhere. And I also had to give up on the idea that I could pause all my actions and figure out the entirety of the completed design in order to have a really seamless build process.  I don’t want to take a month long break to learn SketchUp and figure everything out to the 1/4 inch digitally first, so there are going to be some seams in my build. C’est la vie.

Prepping a Van Floor

prepped van floor
The floor post-cleaning and rust removing, but pre-hole covering.

The amount of floor prep you’ll need can range from almost nothing to a whole ton of work. If you’ve giant rusty floor holes you need to repatch you’ll really have to roll up your sleeves, and if you have a brand new van you can practically skip it. I was somewhere in-between, and had a hard time figuring out how to proceed.

One my regrets in this phase was not cleaning everything really well first with a hardcore cleaner like Simple Green. I kept half-cleaning with the general, natural cleaning products I had lying around and then having to reclean and spot clean. If your surface is dirty, nothing you do to it is going to work right: paint won’t adhere and adhesives won’t stick.

original dirty van floor
The original van floor: I’ve seen worse, but needs a lot of help.

Our van came in really good shape, but was used, so it also came full of racks that were bolted through the floor. When we pulled them out, we had over a dozen little 1/4” wide holes in the floor, some with really minor rust dots around them. There were minor rust dots in other random spots on the floor too. So that all had to be treated: cleaned up, rust ground off with a little wire brush attachment in my screw gun, primed with metal primer, and then coated with protective enamel. 

In addition to the round holes, we also had almost a dozen weird, oblong holes left from removing the rear plastic step cover thing under the back doors. Of the many ways to treat these holes (welding, Bondo auto body filler, adding pop rivets…) the one I was most comfortable with was adhering pennies over the holes with silicon. Pennies are resistant to rust, and fit neatly over the holes…  

Stretched pennies covering the oblong slot holes

Well, the round holes anyway. But what about the oblong holes? Souvenir squished pennies to the rescue! Those weird novelty pennies you stretch out in souvenir machines happened to be the perfect size to cover the slot holes, so I consulted this national list of souvenir penny machines to find one convenient to me. Then I sprayed the whole surface down with Flex Seal rubberizing spray as another preventative layer against moisture and rust.

A complication I had with the holes was that the van floor is grooved, not flat: there are raised and lowered sections. Some of the penny-covered holes were on the raised sections, so if I just plopped my subfloor on that, it would be an uneven mess. I had a friend in a similar bind who decided to glue strips of plywood into the lower grooves to create a flat and supportive “sub-subfloor”, and decided to go with that.

So I cut long strips of plywood with just enough thickness to clear the pennies glued to the higher floor ridges, and used construction adhesive to glue them in place. This also gave me a way to secure my actual subfloor – I screwed the subfloor into those strips to keep it from moving around. The subfloor won’t do a ton of moving, but I’m gluing one big sheet of flooring to it so I want it to hold together pretty well. Oh, and they’re not yellow for any functional reason. I just had a big sheet of yellow painted plywood left over from another project and thought we could use some speedy bumblebee vibes. 

Floor Insulation and Sound Deadening

But wait – what’s in-between the sub-subfloor and the subfloor? Here’s the cliff’s notes, followed by the explanation.

From bottom to top, our floor is:

  • The actual ridged van floor, with pennies adhered over the holes and Flex Seal sprayed over the whole surface
  • Plywood strips construction adhesived into the lower grooves to create a flat surface for the layers above – the “sub-subfloor”
  • Mass loaded vinyl (MLV) for sound deadening
  • 1/2” Polyiso insulation on the flat floor for warmth
  • Reflectix insulation on the curved wheel wells and gas tank, also for warmth
  • 1/2” Plywood subfloor
  • Marmoleum for the finish floor

Sound Proofing

MLV laid down first

If you really want to geek out about noise minimization, there is a fantastic site for you called the Sound Deadening Showdown. I didn’t really want that much information, and couldn’t process it all. It’s like a whole new science to learn, and my brain is already a little mushy (in a good way) from all the other new things I’m learning. I just chose something that seemed straightforward and easy to work with: Mass loaded vinyl, or MLV.

Begging the apologies of the Earth for buying a virgin vinyl product (sorry, Earth! Almost everything else about this van will minimize our resource use – promise!), MLV was otherwise a good fit for what I wanted. All sound deadening products have reviews that they say they worked great, or didn’t work at all – the difference is usually in how they’re applied. One van conversion site I looked at used MLV in a way that seemed really neat and easy and I liked the idea of, but they also didn’t think it was very effective. Which could be because they put it between their rigid floor insulation and their rigid subfloor. I did a little more googling and found a great metaphor for sound muffling on Acoustical Solutions.com:

“If you take a baseball and throw it at a bed sheet hanging from a clothes line, what happens to the ball?  In a very short distance the ball loses energy and drops to the ground. The sheet “bled” off the energy by being able to move in 3-Dimensional space.  Now, I’m not going to bore you with Newton’s Three Laws of Motion, suffice to say that if the sheet could not move, the ball would bounce, and whatever net energy left in the sheet would result in vibration of the sheet.

Now, think about that in terms of sound.  Sound hits wall, bounces, net energy in wall causes vibration, vibration in wall vibrates air on other side of wall, vibration in air on other side of wall hits your ears and you hear it.  Now imagine that the wall is floppy like the sheet hanging from the clothes line…..get where I’m going?”

Now that made sense: MLV can’t really do its job sandwiched between two rigid layers, because its job is to smother and absorb. So instead of sticking it between my floor insulation and my subfloor, I put it on the van floor itself, where it could do maximum muffling.

Floor Insulation

Laying the MLV below the floor insulation also made more sense for connecting the wheel well and wall insulation to the floor insulation: I cut big sheets of MLV and taped them together to coat the whole flat van floor, then taped on additional pieces to cover the wheel wells. Then I cut the rigid floor insulation and laid it down, and used Reflectix (the bubble wrap stuff) to insulate the wheel wells and taped those layers together with foil tape. And I tied it into the wall insulation with foil tape as well.

Some people with constrained head heights skip floor insulation, but we have enough head height to lose an inch or so, and in tiny house world, floor insulation is a really important component of keeping warm. Some van resources say that you can safely skip floor insulation and should insulate the heck out of your ceiling, because heat rises and wants to escape that way. But if you can do both, you should: cold air also blows under the van and hits you from below. That’s why vans, RVs and even tiny houses sometimes have those skirts running along the bottom: to keep the cold air from grabbing your toes.

Subfloor and Floor

cutting a marmoleum floor for a van
The original footprint, with additions and subtractions, as a template for the finish floor.

I saved the rubber footprint that came in the van to use it as a guide for cutting each floor layer. It wasn’t a perfect match, but I cut pieces of it away and taped some big sheets of paper on to extend where I needed it to, and it was WAY better than making up the footprint from scratch.

subfloor in a chevy express van
The subfloor laid in place.

I used half inch plywood for the subfloor – and I paid a little extra for a nice, smooth surface to make things easier for my finish floor later on. The finish floor is marmoleum, a natural alternative to linoleum that’s popular in green building. Marmoleum has a lot of wonderful features but is a little finicky to install, and needs a very flat surface to adhere well and be smooth, so I went with a plywood that wouldn’t give me headaches at that stage.

I cut the subloor pieces to try and minimize visible seams in the floor. The back section is a little wonky but it will all be storage under the bed, so no big deal. The open floor area (all 16 square feet of it or so) will be relatively seam-free. I screwed the subfloor down into those plywood strips in the grooves to secure it, then filled the screw holes with wood filler and sanded the whole floor to get it ready for a nice, smooth sheet of marmoleum.

I won’t go into detail about marmoleum installation, except to say that it wasn’t as bad as I thought! I basically cut out our footprint, laid it over the subfloor, gently folded half of it back like a taco, spread glue down on that half, and rolling-pinned the floor into the glue on that side. Then I got in the other end of the van and repeated that process, starting from where the first glue area left off. I didn’t take any pictures of that process because I was too busy being worried that the glue would dry before I rolled the floor into it, which seemed to be the number one way you can screw up installing marmoleum.  

Squeezing the cut marmoleum sheet into the one part of my yard/driveway big enough to host it.

I watched the official marmoleum installation videos and read PAD pal Kate Goodnight’s detailed post about her marmoleum installation in her tiny house. Luckily the guy we purchased it from was helpful as well, and let us know that in a small space like a van, you can use a rolling pin rather than the 100 pound roller used in the professional installations. You’ve just got to press your body weight down into it.

The weather also really helped us out with the installation – it was recommended to us to warm up the material with a hair dryer when working it into place so it didn’t crease or snap accidentally, but instead we just installed it on an 85 degree day and didn’t have any splitting issues. The installation instructions also said to keep it at 68 degrees for a full seven days after installation…which just wasn’t going to happen. But it was so warm that with a dinky space heater keeping it warm at night, we probably were able to keep it between 60 and 80 degrees for 48 hours, and at that point the glue was mostly dry. Which we declared good enough, because nothing bad happened! Sometimes that’s all you can ask for.

marmoleum floor in a campervan
Ta-da!

What’s Next?

You might be thinking: “What’s up with your walls in all these pictures? Nothing to say about that?” Well my next post will be all about the walls, which I was working on in concert with the floor, but it’s easier to discuss them separately. Plus this post is already ridiculously long. More soon!

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