Installing the Subfloor

Installing the Subfloor

April 25, 2015 Categories Camper Van

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I finally got around to starting on the flooring in the She-Beast today. I’ve been distracted trying to ensure the cab area isn’t leaking water (which it still is), but it has irritated me to the point I’ve decided I just need to move on and come back to it later. The driver’s door isn’t sealing correctly and is letting water in, but the weather seal looks in decent shape. It’s almost as if the door itself is bent outwards just a smidge.

I started the subflooring by filling the gaps between the ridges in the sheet metal on the floor of the van with strips of Reflectix (which is essentially bubble wrap with sheets of tin foil on each side). Reflectix only has an R-value of about 3, but almost every camper van conversion project I’ve read about uses it because it’s good at keeping cool air inside when it’s hot out and keeping warm air inside when it’s cool out.

Once I had the gaps filled, I laid down an entire sheet of Reflectix insulation to cover the entire floor. The most important and time consuming part of this was cutting around all the pillars, gas tank filler tube, and the wheel wells; I wanted as close of a fit as I could get. I used aluminum foil tape to seal the joints between the different sections of insulation, as it only comes in 48″ wide rolls. The wood blocks in the photo are just to weigh it down and keep the wind from blowing it around.

Now that I had the insulation cut and in place, it was time to prepare the plywood that lays on top of it. I laid out three sheets of 1/4″ OSB to create one giant 12’x8′ rectangle. The Reflectix layer I just cut created a perfect template to lay directly on top of the OSB and trace out using a marker, as you can see below.

With the template traced out, I put the Reflectix insulation back in the van. Then I grabbed the jigsaw and started cutting (beginning with the sheet that sits directly behind the seats). As I finished cutting each sheet, I went ahead and installed it in the van. Since I had a great template, each sheet slid into place very nicely. It didn’t take too long to get them all cut and laid into place. I used self-tapping sheet metal screws along the walls to hold the plywood to the floor. I didn’t put any screws down the center because the screws don’t sit flush and I can’t recess them since it’s only 1/4″ thick OSB (they’d break right through).

Now that I have the subfloor in place, I can start laying out everything else. The entire rear half will have another level of flooring installed that will sit about six inches high to allow enough room for my storage system to go underneath it. Even with the raised floor, I can still stand up straight in the rear half. However, once I insulate the ceiling and board it up (which will take up 3-4 inches), I’ll have to tilt my head just a little in that area. Since that will be my couch/bed area, I won’t be standing there much anyways. I’ll still have four feet of space in the front half where I’ll be able to stand up completely and stretch out.

40 thoughts on “Installing the Subfloor”

Jacob · April 14, 2016

Good job! Smart way to trace the ply to get it right the first time.

Beth · April 24, 2016

Great step by step! I will be following your idea for my own trailer mod.

Jon · August 23, 2016

Great and easy to follow! What was the overall cost in transforming the van to a livable area, from insulation to curtains?

Luke · August 23, 2016

Because I went way overboard, it cost over $7,000 for everything I did. And that’s not including the cost of the van. The entire electrical system by itself was around $2,300. Some stuff I never even used, like the water heater and portable furnace. Other stuff I only used a few times, like the microwave, stove, and refrigerator.

The solar setup, running water, and the wall-mounted fans that I eventually added are the only things I know I’d do again, as those were luxuries that were nice to have, especially while living out in the desert for a couple weeks.

Lucas · September 17, 2016

I loved the idea for the template using the insulation. What kind of screws did you use to fasten the plywood to the new floor? I am in the planing stage to convert an 02 Chevy Astro AWD:) Being that I only spent 2k for the van I am not going to be spending too much on the interior. I am going to be scrounging supplies over the winter here in the Twin Cities and stock piling them for spring:)

Carey · February 9, 2017

Hey Lucas, I’m doing the same thing! Like actually the same thing. I jut bought an Astro van for 2 k and am building it out at low cost. What plans did you come up with?

darcy · September 23, 2018

how did your van turn out? We just got an AWD astro and are converting it :)

Thomas Buzzi · March 7, 2017

Just did the same operation myself. I used pattern felt I had lying around from my floor covering days to cut out first the 1/2 styrofoam with bonded aluminum layer and then used that to pattern some 5/8 plywood I also had lying around to keep costs down. I can’t stand up anyway since it is not a turtle top van. Will use foil backed side wall insulation too but not the roof since aluminum foil blocks cell phone reception. (Found that out the hard way).

Claire W · March 15, 2017

Do you find that the bubblewrap-foil insulation was enough? or would you have also added a rigid thicker type of insulation?
I’m just about to start my conversion project, and insulating it is one of the first things on my to-do list.

Luke · March 20, 2017

I would have done a lot of other things differently, but the insulation was more than enough for me.

David Albright · April 23, 2017

Please just do ONE thing. Use PLYWOOD, preferably pressure treated or marine grade. For the area it is not much more expensive. OSB swells and falls apart if it gets wet. You can thank me later!

Luke · April 23, 2017

If you’re expecting water to be freely sitting under/on your floor, you’re already doing something wrong. If you build something properly, you won’t have to worry about water being where it’s not supposed to be.

Richard Chambers · June 11, 2017

You might want to consider the chemical exposure from the treated (CCA)

At least unhealthy using treated lumber indoors.

Steve · February 3, 2018

You never want to use pressure treated lumber of any kind, inside, because it’s toxic.

Terressa · April 26, 2017

Did you use the sub flooring itself as the floor or did you put flooring down over it? You could have sanded the sub floor to smooth it out, stained it and put a sealer on to make awesome faux hard wood floors.

Luke · April 26, 2017

I put flooring over it. I don’t think I’d like the look of sanded and stained OSB. I wanted a rustic look.

Terressa · April 26, 2017

Just finished all the articles. BEAUTIFUL!!!

Scott in MN · May 1, 2017

Wrong use of Reflectix. Manufacturer states that a 3/4″ air space must be used or product is essentially worthless.

Luke · May 1, 2017

Hot damn, that’s good to know! And would help explain why my van was an oven. For anyone who wants the information from the source, go here and click on “Why are Air Spaces required (in every application)?” or watch this video:

Alex · May 13, 2017

Awesome step by step. I am just curious how you finished off the step by the slider door?

Luke · May 13, 2017

I didn’t. I was going to, but got impatient and just wanted to start traveling, so that’s what I did.

Roger · May 26, 2017

So, if Reflectix is not suitable because it requires an air gap, what should be used?

Walt · September 22, 2017

Back in the 70’s when custom vans were everywhere, we put down tarpaper then plywood, then carpet, or whatever kind of floor covering you wanted.

Lee · July 20, 2018

Dow styrofoam rigid insulation.

Tammy · June 5, 2017

How do you achieve the air space?

Luke · June 11, 2017

Daniel Chen · June 17, 2017

One of the best online visual explanation on sub floor install for a layman like me.

Cara · August 3, 2017

I am thinking about using 1/4 plywood on the metal floor and Lifeproof vinyl planks (or Armstrong planks) as my flooring. I have read other people finding value in preserving the grooves in the floor for collecting/managing condensation. Also, the guys at Home Depot convinced me that I would not need additional insulation to what is already part of the planks. Does anyone have any thoughts about this plan?
This design will cost about $175….. not sure how much a system with insulation and vinyl sheeting will cost.

Tim · September 5, 2017

I metal anything roof /floor/side, walls conduct and transfer, heat/cold better than any other product .

Tim · September 5, 2017

I believe your best solution would be to
1. Leave a small air gap on the top bottom and sides .5 to 1.5 inches.
2.Then put foil backed OSB toward the gap( reflex’s the heat/ cold and slows down radiation and convection.
3. Install foam-board on OSB surfaces ( no foil…. thickest on floor and ceiling, sealing as best you can).
Remember the weakest link in the system , windows doors and any opening There is a point at which additional insulation is a waste of money and space. Closed urethane cellulose foam is the best, most expensive too. Think of an ice chest . Also 80 % of light is heat !
4. Interior surface treatment ….light weight , doesn’t conduct heat or cold , is comfortable , cost , looks good ,ease of installation. (Listed in order of importance, to me).

These are a few of the principals I have incorporated into structures I have built in the last thirty years and there are many factors and variances that would need to be addressed. Any structure rolling or stationary…. heat exchange /conduction has similar properties.

Tim · September 5, 2017

CORRECTION: 2.Foil backed foam board with air gap on sides and top ,1/2 in. foil backed OSB on floor with air gap . To create the problematic condensation you would have to have a lot of moist air movement or a water leak or something of that nature. Pretty unlikely but not unheard of.

Tim · September 5, 2017

I don’t like to make controversy. BUT Luke’s May 1st. post and other of his subsequent post may shed some light on why his build was so hot….
You can put a potato directly into live coals the outside will get hard and burn before the inside is totally cooked . Wrap that same potato in foil , it still gets cooked but more evenly. The potato skin inside the foil casing is tight. The heat is still transferred but at a moderate rate . If you could put an air gap between the coals and the foil it would cook slower. If you put insulation between the foil and the potato, even slower still.

My build has :
1. White roof outside.
2. Wood furring strips 1.5 in. It gives the foil a chance to work at cutting the radiation factor of the hot metal.
3. 1.5 inch foil backed foam board on top and sides. gaps filled and seams taped with foil tape used in HVAC plenum construction. .5 in. OSB on the furring strips on the floor 12″ on center .
I used industrial carpet squares on the floor . Looks good, cheap, easy to clean, easy install, and wears good, and never feels cold or hot to bare feet.
4. Side wall are Western Red cedar, rustic cabin appearance.
Cheap…. ( 5/8″x 6″x 8 ft. Fence picket around $4 a board at Lowe’s or HD) Does not conduct heat or cold . Looks good, smells good , easy install
( sprig nails through to furring strips.) Increases the structural strength of the build.
One problem is that the wood shrinks as it cures so paint the foam insulation with a cheap dark color …brown or black /grey. prior to installing the cedar.

Luke · September 11, 2017

I mainly believe it was hot in my van because I was mostly in the desert and it was anywhere from 90 to 115 degrees outside, depending on where I was. During the day, my van stayed around whatever temperature it was outside – which I took as a win, since most vehicles get hotter inside than it is outside. However, during the night, it retained that heat and stayed above whatever temp it was outside.

Kim Streeter · June 7, 2018

Hi Tim.

Could you send me some step by step photos of YOUR build? Sounds like you have some great ideas.

Thanks a bunch!

Ryan · November 21, 2017

Moisture will be your biggest enemy. Always consider this. Your vans steel walls are like a beer can, they sweat, the water will follow the walls down and pool under the floor unless there is a way to vent it out. I was thinking of using spray foam on my next van.

Chelle Mayer · February 3, 2018

What is the best way to handle condensation on the floor?

John · February 9, 2018

Today’s technology is miles ahead of what we had in the 70’s.
My next conversion will have spay foam insulation instead of 1 1/2 “ ripped 2×4’s with r-19 fiberglass insulation. I will still have weep holes drilled in the bad for any weeping (beer can effect) that may occur.
The finsishes of today are lighter and sturdier than back a day as well I used 1/2 rough sawn, dark stained paneling on the walls, carpet on 1/2 interior plywood over during striped floors and 2×3” plus ply and carpet for the couch/ bed.
Lights, stereo, who could have asked for more in 1973? Lol

Patricia · February 18, 2018

I used 1/2 in foam board strips to cover the gullies app in my Promaster metal floor. Added another 1/2 in sheet of insulation foil side down, then a half inch sheet of plywood…then a cheap carpet made out of brown plastic bags. Ended up adding a plush carpet as the foot was too hard for my old knees

Rick · March 13, 2018

Hi Luke! I’m a little late to this party but am stoked about the info provided. I have an ’02 Astro AWD that I am just starting to convert. I have removed the metal shelving which came with the van and still have the rubber matting on the floor. From the looks of things, it seems I should yank it out prior to putting down the subfloor. Thanks for the info on what you’d do differently. I’m going solar with the thought of powering a small fridge, fan and some electronics (laptop, music, battery charging, etc.). Gray birch veneer for the walls with appropriate flooring. Any thoughts on layout? Stooping is required inside the van and my traveling companions would be a couple of dogs (for now). Thanks for any feedback and the info already provided! Rick

Gary K Trenkelbach · September 8, 2019

Just a thought but OSB has a tendency to swell with moister and was wondering if you thought of painting both sides and the cut edges with paint to protect the OSB

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