how did you attach you floor "joists" to the metal bus floor? and not sure how far along you are but i would have the same question for the walls? thank you!!

We decided to go with a 'floating' floor so none of the subfloor material is attached to the metal floor of the bus. After sealing up all the holes from the seats and other things we didn't feel like putting more back in. Definitely up to you on your project but once we get all the cabinets/kitchen layout, couches, and a wall or two built in that floor won't be going anywhere (as well as it doesn't move side to side right now) since I put down plywood over top of everything you see in the picture and screwed that into the 2x4's between the foam board. Regarding walls, we toe-nailed the bottoms into the floor and 2x4's beneath and then used long self-tapping metal (decent sized) screws to attached the top of the wall studs to the metal ribs on the ceiling and those feel extremely solid as well.