A Floating Subfloor

Disclaimer: Rust SUCKS.

I spent three days sanding down the floor, but every morning when I went back out to the bus the rust had reappeared overnight. I spent the first two days taking my time while sanding the floor to make sure I got every speck of rust, but as I said the small amounts of rust would reappear overnight, so the third day I re-sanded the entire floor in order to paint the next day. After finishing sanding, it’s important to close up all the holes caused by the seats. We used plain silicone for most of them, and flex seal spray for one of the bigger areas. Then we covered the floor with two coats of Rust-oleum Oil-Based

Metal Primer from Lowes to seal it. I’ve seen other buses use pennies to cover the holes as well as silicone, but there's mixed information on if that causes more rust which is the exact opposite of what we wanted, so we stuck with silicone. The whole process took about four days. It probably could have taken less time, but there’s a learning curve to everything. The

biggest learning curve about building a bus is realizing that EVERYTHING takes longer than you think it will, without fail.

After waiting the rest of the day for the paint to dry, it was time for the subfloor.

After doing extensive YouTube research, we decided to do a floating subfloor. This means that the subfloor is screwed together, but not screwed to the floor. I chose this option because it’s not only important that everything in the bus is flexible, but also because it didn’t make sense to me to drill more holes in the floor after spending so much time waterproofing the floor. Insulation comes in 4’x8’ sheets, and so we put 2x4s in a frame around the edge of the floor and wheel wells. Then put down 2” insulation with a 2x4 about every 3-4 feet. Then I used insulation tape to prevent losing too much R-value between the insulation and the wood. 2” insulation has an R-value of about 12, whereas 1 ½” insulation’s R-value is about 9. If you decide to use 2x4s and are trying to avoid cutting the plywood too much, make sure you place your 2x4s every four feet. Standard building size is 4’x8’, so you might have to cut the length of everything down a bit depending on the size of your bus.

Pro Tip: The little trap door on your floor is the access to your diesel tank should you need to work on it. Make sure you know where this is, and cut the hole out for it in your subfloor. It’ll save you a lot of time in the future, trust me.

I’ve seen other builds use only insulation without the 2x4s. The argument here is that wood has a low

R-value of about 4, and by only using insulation your subfloor will have the highest possible R-value. I’ve also seen builds use a very similar set up to mine, but with 2x4s going down the center as well to help with the inevitable compression of the insulation with excessive walking. If you do end up using 2x4s or something similar, take the extra time and money to use insulation tape because it will help with the overall R-value of your floor. Other builds don’t even take the original floor out. I think it’s important

to take the floor out so that you can see your foundation and make sure it’s sturdy enough to build on, but by no means am I an expert in bus building. This was what I thought was best, but do as you see fit for your build. Then I covered the insulation with ¾” plywood to complete the subfloor. In total this took almost 3” away from the interior height of my build. My bus was about 6’- 6’ 2” with the original floor, but luckily I’m only 5’7” and so losing some height was worth the extra insulation for me. If you’re on the taller side, and trying to avoid a roof raise, then this might not be the case for you. Do as much research as you can until you feel like you can make an informed decision. I decided this was the best in order to balance between a high R-value and the subfloor being structurally sound.

After finishing the subfloor, I tried to unscrew the walls to reinsulate them as well. Which worked for the most part, but the top of the walls were tucked underneath the windows. Other builds have taken out the windows in order to close off some sections, to

reseal them, or often with a roof raise they take all the windows out and replace them with RV windows. I decided not to do that because I hadn’t experienced any leaks so I felt that they didn’t need to be resealed. I also wanted to keep as much of the bus as original as possible, and so the windows inevitably stayed. This meant that we had to use an angle grinder to cut out the top of the walls. The insulation in the walls was pretty terrible, so we replaced it with more 2” insulation. I framed the walls with 2”x2”s going along the length of the bus, and at every cross section. I used 2 ¾”self-tapping wood to metal screws to attach them. Hindsight is 20/20, and now I feel that this was a bit overkill. Especially between the windows, I feel like this wasn’t necessary, and instead of using trim it could have easily been refurbished with paint instead. The next technical step would be to close in the walls, but I wanted to see a little bit more progress so I ended up building the couch shortly after this. Once again, if I could redo it I would have closed in the walls next just to prevent less hassle in the future. Next up is deciding on my floor plan!

Thanks for reading, and enjoy the Sweet Life!

-Hannah