AIRSTREAM RENOVATION: Cutting and Sealing the New Subfloor

Before we start cutting and sealing the subfloor for our Airstream, we need a... subfloor.

We got the plywood for our subfloor at Lowe's. The original thickness was 5/8" but I couldn't find that anywhere, so I went with 19/32 which is 1/32nd thinner than 5/8" if I remember correctly... I could go check but I don't feel like it right now. Our trailer is a 31 footer, but the shell is only about 27' and to cover that length I needed 7 4'x8' sheets, but I got 8 just in case I screwed one up. Always be prepared!

I brought the wood back to the house, dropped it off, and left it for a couple of weeks because that's just the reality of projects like this. When I was finally ready to work on it, the first thing that needed to be done was cut the boards down to the width of the chassis. I wasn't really sure the best way to approach this but I figured if I used the curved c-channel as a template that would give me the appropriate width. So I laid out that c-channel on top of one of the plywood sheets and traced it. I used a jigsaw, which I had never used before, to cut the curves.

I then tried to get the c-channel onto the wood. No go. So I had to continue to shave it down until it fit. Once I got it to fit, I took the board with the c-channel on it and laid it out on the chassis to line it up with the screw holes in the frame to make sure it fit right.

After, struggling with it for a while, we finally got it to line up pretty close and I figure that was the best we were gonna get, I had some wiggle room with the c-channel to be able to adjust it if need be.

Once that was on, we just measured the width and cut the other boards to match and went down line.

Mind you, I am feeling pretty rushed at this point because it's the end of October and winter is coming fast. I need to get these boards sealed before it gets to cold because it needs to be warm enough for it to set. I also need to get the shell back on before it starts to snow and move the Airstream off of the side of the road and out of the way of the snowplows.

Back to the drawing board

So we gave up on day one of getting the subfloor boards cut. I think we got 4 boards in when we realized that we were starting to go crooked. We went back and realized that the first piece at the front end was not squared up. It was about an 1/8th of an inch off. So we went back and shaved some wood off the corner that was an 1/8th inch too long and finally got it to square up. Another revelation we had was that the plywood should be 91.5 inches wide. (For a narrow body trailer) Once we got that number everything started to fall into place and things went much faster.

For the wheel wells I just laid the boards in their correct place, and one at a time traced the wheel wells from the underside onto the plywood and cut out the notch. There were also several holes that had to be cut for the plumbing and electrical that comes up through the floor. That was a little bit of a mindbender but I managed to get it done!

For the end piece, which is also curved, and it's also curved to the same exact dimensions as the front. I took the front piece that I already did the excruciated and tedious work on, and used that as a template. Cut it out and it fit perfect! Now we are on a role, baby!

Lacie's first time using a power tool (besides a drill)

Prepping the guts

Now that all the boards are cut to size and off to get sealed, I need to make sure I get everything in place that goes underneath the subfloor before I lose access to it.

Tank Plumbing and electrical

One thing was extending and running the wires from the tank heating pads and sensors, making them extra long so I can run them out one of the holes and make sure I have plenty to work with when the time comes to do all the electrical.

I also needed to make sure to run a pipe from the outlet of the fresh water tank over the other side of the trailer where the water pump will be. For this I used a piece of Pex Pipe. I bought a 100ft role of both blue and red pipe, for cold and hot water, and this should be enough to plumb the entire trailer.

Need to be able to stop

The second thing I need to have in place was the brake wiring. The brake wiring gets ran under the subfloor and above the belly pan to protect it from the elements and critters that might like to chew on it. The last thing you want on a 8-10K lb trailer is a chewed-up brake wire....

I bough the Deka Jacketed 2 Wire, 10 Gauge, Brake Wire from, they sell it by the foot so measure it out and get a little extra than what you think you need.

I ran it down the frame from the front, with a nice coil of extra wire to play with, and I had to split it four ways to go to each set of brakes.

I drilled holes in the belly pan and used these perfectly sized rubber grommets I found at the local hardware store to protect the wires from rubbing on the sharp sheet metal, and seal up the holes. Now that's a job done right.

The other thing I almost forgot about was the step support and cover. There are a couple of metal plates that go over the outriggers where the steps are just to add extra support, as well as cover the plywood from being exposed since no belly pan goes where the steps are.

This was also Lacie's first time using the rivet gun.

Sealing the Subfloor

It's a known fact that Airstreams leak. It's going to happen. Even though we will do our best at the getting the shell all sealed up, the fact is that the trailer is going to be moving down the road at 60+ miles an hour, hitting bumps and dips, and we plan on boondocking so I am sure there will be some rocky roads in our future. and I don't just mean ice cream. The point is the trailer is going to get shaken up, LIKE A LOT. This is bound to cause something to come loose and cause a leak somewhere. Even if it's just a small one.

Soooooo..... Make sure to take the extra precaution of sealing the subfloor to protect it from water damage. I mean, even if the shell doesn't leak, water is bound to spill from the shower or sinks or from the kids somehow...

My plan was to use a marine grade epoxy from TotalBoat. But I didn't plan very well, or didn't understand what I was getting myself into, because I ordered two sets but it still wasn't enough to cover the area I needed to cover. I realized this after I got one board completely coated (on only one side) and realized I'd gone through about 1/4 of what I had.

Side note, I've never really worked with epoxy like this before and it was super hard to paint on. I feel like it took 20 minutes just to do one side of one piece of plywood.

Well, I didn't have time to order more, nor did I want to purchase more because each kit was $50 for apparently nothing. So I made a new plan to only do the outside edges of the wood with the epoxy, the edges that usually get the most water damage on Airstream. And then I would do the rest, the centers, with a regular oil based sealant which I could get for cheap at the hardware store.

But in the meantime, the temperatures dropped below what I need for the sealant to dry so I had to take them all up to Hailey and pain them in my tiny garage with a space heater. It took me about a week to get them all done. But dagnabbit I did!

Salvaging the C-Channel

I saved about half of the c-channel. The straight pieces are cheap enough so I got rid of the most corroded and distorted pieces. For the ones I am salvaging I want to make sure to clean them up real good by getting all the corrosion off, so they don't continue to corrode. For this I used my trust brushless drill and some wire brush attachments. As well as just some handheld wire brushes. The trick though is to use brass brushes. Steel is too hard and will take off too much aluminum. Since aluminum is a soft metal, you want to use another soft metal like brass, to brush it off. It will definitely still give you a brushed look, so if your doing this on something that is going to be visible, you may want to polish it afterward. Unless you're going for the brushed look!

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Ben Figueiredo

I make a living as a filmmaker & Website Designer, Telling Stories, creating content for businesses, entrepreneurs and even couples getting married. As a Five on the Enneagram, I love learning. Absorbing as much knowledge I can. I am into Biohacking, holistic wellness, and Rewilding so that I can be the best version of me to enjoy life with my family connecting with nature, our community, and God.

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