I finished the floor install this weekend...
It was a long, arduous process. First, I had to secure the flooring I wanted (hexabirch plywood). Almost nobody stocks that in CA, but I found an RV upfitter in Salt Lake City that had sheets of 1/2" 4x8 sheets. I coincidentally was going to be going through SLC last fall so I arranged to stop there and pick up three sheets. Wonderful people and it worked out great.
Check out the shop if you are in the area or looking for parts for builds, they have been increasing their web presence a bit:
NaPly Riga Heksa is ideal for camper and Sprinter construction. Order this weatherproof, non-slip plywood from one of the USA's only licensed distributors.
reparadise.co
They also stock some Dometic products and other things. I ended up buying a handful of items from them, including a pair of Lion batteries, a sink, faucet, drain, the plywood... it was a pretty big haul. Wonderful people, and they are making some impressive conversions, too!
This is what the hexa birch looks like. The scale is relatively small, about 3/8" across the hexagon, and I think it will be quite sturdy and non-slip with wet shoes. The tape in the photo below is 3/4" painter's tape (three pieces slightly overlapped) that I'm using to mark the future wall members.
My flooring cross section is as follows:
3/8" closed cell foam in the valleys.
1" XPS on top of that flus to the ridges.
1/4" birch plywood subfloor, glued to the XPS and the wood underneath (more on that in a minute).
1/2" hexa birch plywood on top of that, glued to the subfloor.
I staggered the seams of the XPS, the subfloor, and the plywood floor, so there won't be any softness in the plywood floor. I made a 1/4" lap joint in the 1/2" plywood with the router and some 1" strips of the subfloor material. The lap strips were glued in the rabbet in the one side in the shop, and then in the van when the final floor installation occurred, I glued the strips onto the other overlapping rabbet in the abutting piece to make them a complete, contiguous top layer. I used Gorilla glue for those joints because they are wood to wood and this would make them extremely strong. At the same time, the top layer was glued to the subfloor with Locktite PL 3X.
On the edges of the floor and wherever the structure is (the galley and the bed and garage frame), I put in some 2-1/2"x1" pieces of wood instead of the XPS foam. These were glued directly to the van deck using the PL 3X glue. This is so that there is a bearing capability in the floor wherever the points of concentrated pressure will occur (the structure, wherever we will step into the van, at the edges, in the corners, etc. Also, I did this where the tie-down screw holes are so that I could bolt through the floor and have a really solid bearing surface for the bolts.
Here is a photo showing some of the XPS and the wood framing that is under the subfloor. I the photo, you can see the edge of the floor at the sliding door, the reinforcement rectangle for the bench, a block to the right for an L-track point, and a pair of 4" pieces that will be where the heater is mounted. Above that, there is a block with a hole in it located at the van tie down location just in front of the wheel well:
The edge of the flooring is built up with a piece of aluminum angle to clean it all up, and when the floor is done, it will have a piece of aluminum stair edge nosing on the top corner, so it will be nice and clean.
Photo of the wheel well and the tie down bolt. This one will be hidden in the structure of the bench when finished. The heater will be in front of it.
Full van with the galley carcass in the approximate final resting place. One drawer is in the carcass. The remaining are waiting for assembly in the garage.
Before I install the carcass in the van, I'm going on a run to get the birch plywood for the bed and garage area... After that, the galley can go in temporarily and I can start locating all the large electrical items on the passenger side, and get the majority of the electrical run throughout the walls and ceiling.