The next step in our quest to DIY RV were the interior walls. Because this bus was to serve as a potenial 4 season home, I needed to make sure it could stay cool or hot depending on our needs. Time was short however, and I was limited to working one day a week. It seemed best not to strip the entire interior down to the bones, but to simply insulate the existing structure. If I had had more time, the choice would have been different but at this point it seemed that quick and dirty was the best route.
The only tin removed from the walls was that above the windows, the frame-work that would hold the walls needed to mount directly onto the steel ribbing of the bus. I ran a top plate across the now exposed ribs, gluing and screwing each 2x2 in place. The screws I chose to use were self-tapping monsters and expensive, but these walls needed to stay in place despite constant road vibration.
Instead of going straight to the floor with my framing, I decided to mount my sole plate on the steel ledge that ran the length of the bus 9" above the new floor. While this decision would cost me a bit in terms of insulation, it would give me the ability to place break-away panels down the length of the bus where I could run wiring or pex plumbing lines and service them without tearing the whole wall open.
Choosing, as we did, to keep all the original windows, we removed the screws holding them in place, using the new studs to act as window anchors. We went through 2 tubes of PL during this process but strength was a priority. After running braces below each of the windows, the framing for the most part,was done. It looked kind of good.