The Many Steps in a Great Subfloor

Building a van has far more decisions than I even thought possible.  Believe it or not, the subfloor was no exception.

With all the large exterior holes cut and filled in for the MaxxAir Fan and the Sliding Window, we could finally begin the interior projects.  While many can debate about doing the subfloor before cutting holes, we opted for after.  Since we had the interior upgrade package, we had something to cover the floor.

The subfloor had a surprising number of steps involved.  It took us close to a week to complete the project.  Unlike the holes in the van, we had the luxury of closing the doors when we needed to pause on this project.  No need to worry about weather windows and rain coming in through a hole in the van!

The Many Methods of Creating a Subfloor

When you scan the YouTube, Blogs, and Instagram, you will see hundreds of ways to create a subfloor in a van.  Why is this?  Because everyone has specific needs in a van, everyone tweaks the subfloor to fit them.  For example, a very tall person over 6ft will want to raise the floor as little as possible.  Or, someone who frequently has very cold feet might increase the height of the subfloor to accommodate more insulation or radiant floor heating.

The number of decisions to make when approaching even something that seems basic is actually a little ridiculous.  For real, check out YouTube (after you read this post, of course) for “Van Build Subfloor” and you’ll get a wide range of styles and options. 

Our Subfloor Plan

After combing video after video and blog after blog, we came up with our own plan.  We wanted both insulation and airflow with a strong foundation to hold our kitchen cabinets.  This would also allow us to secure a bench seat adequately to the floor.

Since we are not the tallest of humans, we knew we could raise the floor a bit without difficulty.  At 5’2” and 5’9” we would have plenty of space.  With nothing in the van, the Ford Transit’s High Roof option allows for 6’5” in the center and around 6’2” on the sides. 

Subfloor Furring Strips

We decided to use a set of furring strips to begin.  Since quite a few of them laid around Karma’s Dad’s garage, we opted to use what already existed instead of buying fresh wood.  We felt it more sustainable to reuse or use wood already laying around even if it was not the most sustainably sourced wood in the beginning.

If you’ve never seen the bare bottom of a van, know that it is not flat.  Depending on the length, a van floor will be 2-3 large pieces of sheet metal welded together.  Due to the lack of strength in flat sheet metal, the floor is ribbed. 

Some people place their furring strips length wise in the van from front to back, aligning with these grooves.  On the other hand, we decided to place ours widthwise with wool insulation in between them.  The slightly indented ribs will allow for some airflow to occur underneath the wool and allow for the wool to expand some. 

Again, if we were tall, this might not be ideal.  However, we are not giants and my feet get cold easily.

The First Big Quirk

You guessed it!  Even the furring strips had something to problem solve.  With the furring strips widthwise across the van, at several points the floor ribs were not consistent.  What does this mean?  The structural floor ribs rested in the middle of the van, not close to the sides for each strip. 

This meant that on some edges, the furring strips could create a slope.  We decided to “make” a small rib with pieces of leftover furring strips.  However, it was not simple.  The furring strip was larger than the rib, so we had to cut the furring strip pieces thinner.  Using a 30-year-old table saw was a bit testy to get it accurate enough.  Luckily, we worked with scrap pieces.  Karma exhibited quite a bit of patience as he found the correct height on the fourth try. 

Treating the Furring Strips

We knew from previous experience that the floor takes a beating in a van.  When we come running in from a hike in the rain, the floor gets our muddy, wet sandals.  When we are cooking and accidently knock over a water cup, the floor takes that as well.  As we drop our soaking wet backpacks, they go on the floor.

Therefore, we wanted to protect the subfloor as much as we could.  First, we used two coats of Vermont Natural Coatings, a waterproof coating.  This will penetrate the wood and keep other water on the surface if it manages to get there.  Second, we used two coats of Caliwel, a mold and mildew preventative.  Is this overprotective?  A bit.  However, I really do not want to rip up the floor and replace it because of mold in the near future.

Because of the timing, adding these four coats took an entire day beginning in the morning.  The VNC needed to have the second coat applied while it was still damp.  Thus, the first and second coat went on quickly.  Unfortunately, we had to do both sides.  So, we had to allow the first and second coasts to dry on the tops and sides.  Then, we flipped them over and got a first and second coat on the bottom. 

After the first and second coats of VNC dried, we could add the first coat of Caliwel.  Unlike VNC, Caliwel had a minimum time of four hours between coats.  This meant that we could flip the furring strips and get the bottom as soon as the coat on one side dried, but we still had a four-hour gap.  We also had to do this same process with the square furring strip supports the following day.

Attaching the Furring Strips to the Van Floor

We started by laying out the furring strips where we wanted them on the floor.  Already having planned this when we cut, we just had to align them with the marks we made in tape. 

Since the van is a moving structure, we did not want to use wood to metal screws.  Furthermore, we did not want that many small holes in the metal of the floor that wouldn’t get treatment. 

Instead, we used a low VOC marine Loctite adhesive.  We’ve notices that van builders borrow from the marine folks a lot since both vans and boats have constant vibration.  If at a loss of what to do, we definitely check out marine websites.

We gathered a significant number of weighty objects nearby.  Every lifting weight in the house came out, steel beams, large pool rocks, chopping blocks, anything meant to be heavy. 

Starting with one strip at a time, we moved it back from its alignment and added dollops of adhesive on the ribs.  Then, we realigned the furring strip per our marks and added weight.  After the first one, we got into a pretty good rhythm.  We moved from the front of the van to the back, then searched for even more weight. 

While the adhesive was quick, it still had a 24-hour full cure time.  Once we finished, we just had to wait.

Subfloor Template Design

After our allotted 24 hour wait, we removed the weights and were pleased with the furring strips.  We thought about using the vinyl floor that came with the van’s interior upgrade package, but we couldn’t hold it still enough.  Feeling like we would cut several angles badly, we went onto plan B. 

Plan B was going to the hardware store and picking up cheap 1/8-inch hardboard to use as a template.  We felt bad about it essentially being “wasted,” but we’ve decided to use it for many template needs as we move forward.

When first looking at the van floor, you think it’s the best idea to just put one board completely in the middle and make a lot of smaller pieces to fill in around it.  We did that on our last van and we pulled a lot of hair out. 

Instead, we used three 4×8 sheets.  From our first furring strip, we measured 4ft and made sure the boards would overlap on that furring strip.  Next, we did the same thing for the second sheet.

Like always, the van threw us multiple curveballs.  One pillar right behind the seats appeared to have a right angle.  Not at all.  Because of the door, two sides on the second panel sheet were not as symmetrical as they appeared.

Through trial and error as well as muttered curses, we figured out all the angles on the template.  We had a lot of back and forth from the van and our template cutting station.

Eventually, we managed to cut all three hardboard templates and got them to lay in flush.  This took the majority of a day – at least the majority of our ability to concentrate in a day.

Cutting the Subfloor Birch Plywood

We came back fresh and went to work using our hardboard templates on our plywood.  Since we found out that most plywood contains formaldehyde, we did a lot of research before purchasing the subfloor wood.  We didn’t want to add that to the build. 

A quick note on sustainable plywood.  There is not much.  The most sustainable option would have been hemp board.  However, two of the three major companies went bankrupt a year ago.  Moreover, I did find one company with 25 boards in LA and 100 in Georgia.  But, we would have to expend two tanks of gas to get to LA and back or have it freight shipped for twice the cost of the boards themselves.  Lastly, we checked into bamboo plywood.  It was $300 per 4×8 sheet.  It was beautiful, but nope. 

That left us with Columbia Forest Products Birch Plywood made with soy-based glues.  They had some sustainable forestry certifications, but who knows really. 

Jumping into the cutting process, we set up two sawhorses and laid the hardboard template down over the birch plywood.  We drew the lines from the template and got the jigsaw out.  This time, thanks to the Woodworking Dads blog, I found the correct jigsaw blade at Lowes.  We needed a super clean wood blade with 10-12 tpi.  Check!

I held onto the boards while Karma carefully made all the cuts.  He started using a mantra, “Straight cuts, don’t rush.”  The templates really made it worth the effort when we placed each birch plywood in and it fit perfectly.  Cutting the birch took a third of the time because we did not have any re-cuts to make. 

Insulating the Subfloor

After cutting all the boards, we pulled them back out and began insulating our floor.  While we know it won’t ever be toasty warm, it will make it not ice cold.  We purchased three bags of Havelock Wool to insulate the whole van.  After quite a bit of research in how many chemicals existed and off gassed in regular household insulation, we wanted something natural.  Havelock sourced ethically harvested wool and used a machine to use the fibers in the wool to sew it into batts.  No extra glues or string.

This made it easy to pull a batt out and split it in half.  Half of the batt fit perfectly between our furring strips and the birch plywood subfloor. 

Karma and I fell into a rhythm where he split the batts and I cut them to fit between the furring strips.  We worked smoothly and efficiently.  It also went surprisingly quick.  The wool smelled earthy, and we did not have to wear gas masks and gloves.  To us, this was a win – win.

The Second Big Quirk

At this point, after we insulated the floor, but before we added the plywood subfloor, we had to trouble shoot.  From the extra interior upgrade package that Polysprout already had, we had two wheel well covers and a vinyl step-up. 

For the two wheel well covers, we had to add some modifications.  By that, I mean, we had to cut a few chunks out for the furring strips.  The way they attached it would not have worked if we kept them on before the furring strips.  If we added it after, the attachment points would not line up correctly.  So, we brought out the scissors. 

We grabbed half a batt of wool, laid it across the wheel well, and added the modified cover back on top.  Voilà!  Repeat on the other side.

The sliding door step up was another story.  Basically, we couldn’t keep it in before the furring strips because it would push five of them upward.  But, we could just slide it back in place because of the structuring of it underneath.  Again, we brought out the scissors and began working.  This one required the jigsaw and multiple: cut, check, cut, check. 

Eventually, it worked, and we locked it into place.  We really wanted to keep it for the piece that extended back toward the edge of the door.  Without it, an odd space existed, and it looked more aesthetically pleasing with it.

The Final Subfloor Step

At last, we came upon the final step: screwing the birch plywood into the furring strips.  Since we plan to cover it with flooring, we used Karma’s chalk snap line and our tape centering marks to make a grid.  We placed the screws equal distant across. It was also awesome that we had two drills, so we both got to work on the same task!

The chalk lines made it easy because all we had to do was place a screw wherever two lines crossed.  Piece of cake!  Luckily, we did this math at Lowes and had six screws to spare when we finished.