When we last left off, my Airstream was floorless and, admittedly, looking rather sad. So, in this post, I will show you how to complete that Airstream shell on floor replacement.
Step One: Repair the Frame
After removing the floor, we discovered several locations where the frame required repair. I wouldn’t say the frame was about to disintegrate before my very eyes, but it was pretty clear some sections needed to be replaced, primarily in the front and rear of the trailer. (The same areas where the subfloor was in poor condition.)
If your frame is in simular condition, purchase some new steel, pay a welder if necessary, and bing-bang-boom new frame!
In reality, the process more complicated than that. But now our frame is in much better condition.
Step Two: Prevent Further Rust Development
The rest of the frame was in good condition, but we wanted to prevent further deterioration. To do this, wire brush the frame to remove loose rust then apply a coat of POR-15 or simular product.
POR-15, which we lovingly refer to as tar, is a product which chemically bonds to the rust and prevents further rust development. Fair warning, it’s strong stuff so avoid getting it on your skin (it will be there for weeks) or the lip of the paint can (you won’t get it open again).
I also recommend giving the ground a squirt or two with the hose after painting POR-15 if you live in a dry climate like me as moisture helps POR-15 cure.
Then, since any new steel (hopefully) won’t be rusted, paint that with a coat of rust-preventative paint like Rustoleum.
Ultimately, this is the very fun step when you’ll realize just how many surfaces the frame has.
Step Three: draw a subfloorplan
Each Airstream model and size will have a slightly different subfloor layout. To make sure you know yours, draw a plan of the pieces. To determine the correct layout, you can either reference the original floor pieces or measure the frame. Wood is generally sold in 4′ by 8′ sheets, so any frame members 4′ apart will require one sheet of plywood.
For our airstream, we bought 7 sheets of 1/2″ ACX plywood. Our layout required two 2′ wide pieces, which we chose to cut from the same sheet, and one 3′ piece. Some Airstreamers recommend marine grade plywood for the subfloor, which is superior to ACX, but it was more than double the cost. Therefore, we opted for ACX.
Step Four: Cut and waterproof Wood
With your plan in hand, cut the wood to size. This is a relatively simple step, with the exception of the rounded pieces. If your floor was in good enough condition, you can use the old pieces as templates. If not, you’ll have to employ some educated guessing.
Our trailer’s wood was in moderate condition. Thankfully some of the curved edge was intact and so I essentially played connect the dots and verified my educated guesses with some measurements from inside the trailer.
After cutting the wood, give it a good coat of a waterproofing solution. Don’t forget the edges!
Step Five: Insert Floor
Fair warning, the photo you are about to see is rather disturbing. Viewer discretion advised.
Remember how I advised you to insert shims into the c-channel to prevent it from bowing out? This is the reason I said that.
For some unknown reason, the streetside of the Airstream remained solidly on the frame, but the curbside wanted to bow out. We tried multiple times to force it back onto the frame, but eventually it would pop back out. So, we chose to use this problem to our advantage.
There are two ways to reinsert the wood. The first, which is more common, involves cutting each panel down the middle and inserting each half into the c-channel. Some force may be required to make the two panels lie flat on the frame if you make them rather tight. This is an adequate method if you don’t have any other options, but I was a little hesitant about it.
I’m not an engineer by any stretch of the imagination, but I was concerned that piecemealing the floor like that could cause problems down the road. So, we took advantage of the bowing problem. To insert the floor our way, you will have to let (or force) one side of the Airstream shell to bow out. Then, slide one side of a full sheet of wood into the side of the c-channel which isn’t bowed out. (The last piece will likely be the hardest to insert and may require more fanangaling.) When all the floor is in, enlist a team of friends to help push the bowed c-channel back onto the frame, inserting the wood at the same time. It will be necessary to insert some of the bolts (see next step) while deadlifting the Airstream.
Step Six: Secure the shell to the frame
Next, secure the shell to the frame through the c-channel. Once more, there are two ways to do this.
As you might have noticed, we ultimately chose to remove the underbelly skin. Our underbelly was not in the best condition. In addition to large holes which could be patched, we noticed small pinholes. Since these would only expand over time, so we chose to remove and replace the aluminum. Without the underbelly skin, we could bolt the floor through the c-channel like the factory did. If you would like to use bolts like the factory, it is not difficult to drop just the sides of the underbelly for access. They’re held on with pop rivets.
If you removed the underbelly, purchase stainless steel bolts and lock/stop nuts. We bought a pack of 50 each and had plenty left over. We chose to drill holes up through the wood using the existing holes in the frame as a guide. Then, with a partner, insert the bolt from the bottom and screw on the nut from the top.
If you did not remove the underbelly, purchase stainless steel lag screws and use those to secure the shell to the frame through the c-channel. Because we replaced the rear frame with new, closed steel tubing, we had to use lag screws to secure the rear of the trailer.
Step Seven: secure the subfloor to the frame
To secure the subfloor to the frame, you will be replacing the screws you removed. I purchased 125 floor repair screws from Vintage Trailer Supply. These are self-tapping screws, which will help them stay secure as the Airstream rattles down the road. Originally, I tried to use the same holes because I didn’t want to drill more holes in the frame. But, I discovered that the old holes were slightly too big to properly secure the screw.
So, predrill new holes evenly spaced between the old ones, slightly smaller than the screw. If you have a fancy countersinking bit, use that to countersink the screws and ignore my next instructions. (Free tip: the high speed setting on the drill is best for drilling through the metal frame.)
If you don’t have a countersink bit, then use a drill bit the same size as the screw head next. This will allow the screw head to sit flush with the floor. Drilling to the right depth may take some trial and error. Although the Vintage Trailer Supply website says the screw will countersink itself, I found they needed some help.
Finally, change to a driving bit and the high torque setting, which will make it easier to tighten the self-tapping screw.
Just 124 left to go.
Step Eight: Walk around like a normal person again
I honestly had no idea how nice floors were until we didn’t have one. We were either balancing on the frame or clambering over it for months while doing this project.
The official Airstream inspector was also ecstatic about our progress.
Now, dust off your hands and take a moment to lay down on your new and improved subfloor. You deserve it.
More updates and how tos coming, so stay tuned!