After cleaning up the rust and sealing it, I was finally ready to begin adding to the van. The first step was to install the subfloor. I decided to insulate the floor with spray-foam insulation to add a little heat retention. Since the floor is corrugated, this had the additional benefit of evening out the floor to provide a solid base for the subfloor.
After spraying foam into the corrugations, and deformations caused by the previous owners, I trimmed the foam down to a uniform surface.
Next came installing the plywood subfloor. Because the van floor was deformed, I wanted a heavy subfloor. I opted for 3/4” plywood. I then created a template of the entire floor out of construction paper. Using this template, I cut the subfloor to shape out of 3 separate sheets of plywood.
Once the subfloor was cut, I drilled holes through the plywood and metal van floor so that I could bolt them together. I countersunk and hammered t-nuts into the subfloor, and then ran bolts and lock washers up from below the van in order to fasten everything together.