VAN Subfloor: Please provide your Suggestions/Ideas

[justfra]

Hello people,

TL;DR:
For the subfloor I have seen 2 approaches mainly:

• Timber frame glued on top of the van metal floor, rigid foam insulation between the framing and plywood on top. No screws across the van floor to secure it.
  
• Lighter insulation, maybe just sound deadener and plywood, or strips of rigid form board along the gaps and then plywood (with or without maybe another 1/2 inch layer of rigid foam but definitely thinner than with the first approach), then plywood, secured to the bottom of the van.

I'm not sure if it's just a coincidence but seems that who goes for the first approach with the framing, doesn't secure the subfloor to the van, or if there's a reason not to do it in that case.
What do you suggest, what do you think it's better and why?
Also take in account that we are beginners.

Long story
Me and my wife got ourselves a Ram Promaster, bought most of what we think are the basic tools we need to get started on the conversion of our soon-to-be home.
We are complete beginners so that comes with a lot of beginners questions and doubts.
I have spent literally hours on a daily basis in the past 6 months trying to look at all aspects of the conversion and in some ways I feel less ready than before (not discouraged, don't get me wrong!).
I figured to avoid analysis paralysis we need to get started. We will make mistakes (hopefully that we can fix) and learn from them. It's time to start!
The main questions/doubts are above. Money is not a huge concern in the sense that if something makes really a difference in terms of quality/durability/effectiveness/ease to install/space/etc. (too much?) we are willing to spend some more because we plan to live in it full time.
Another (silly?) doubt I have is... When people drill a hole from the bottom of the van all the way up to the plywood, they paint to avoid rust only on the bottom of the van.. Shouldn't they be painting on the inside, too? Can't that part rust?

Well thanks in advance,
Hope we can get this started as soon as this weekend maybe.

 

[maki2]

You could screw the panels to the floor.
But an alternative is to adhere ridged foam (the pink or blue stuff) to the plywood. Then use some blocking or brackets at the edges and secure it to the sidewall framing. As long as the plywood panels don't shift or lift it will be stable. You are going to be putting more weight on top and the "furniture", cabinets, beds and such will also be out along the walls and they will also be secured to the walls. So they will help hold down the floor. Often you will have the base of the cabinets secured to the plywood subfloor which acts as yet another constraint of movement.

Keeping things well secured is all about constraining movement. It takes three points of constraint to secure something. For instance the floor of the van is one constraint to keep the panels from moving lower but you also need to keep it from moving upwards. The other constraints keep it from shifting sideways along the plane of the flooring. Whatever you want to keep fixed in place has to follow the concept of constraint. After a while of practicing the skill of learning to think "constraint" it gets much easier to design things.

 

[MrNoodly]

All I have on the floor of my Express is the padded rubber mat that was a factory option and a couple of small throw rugs. It serves my purposes just fine while consuming minimal vertical space. If the floor gets too cold, I keep my shoes on.

If you want a subfloor (which implies something else over it), go ahead. If you cut and fit it snugly enough you don't need to fasten it down. The fit will take care of lateral movement and the weight of the stuff in your van will take care of vertical movement. However, over time, the little micro-movements of the subflooring will wear through the paint.

 

[B and C]

I think most just cut the plywood to fit the floor and do not screw through the floor. Be aware of what is underneath if you decide to go this route. You don't want to be puncturing things like brake and gas lines. This fit keeps it from moving laterally. You could use any building method you want based on safety and how much weight/room you have to work with. Cabinets affixed to the floor and wall will take care of any movement.

Think lightweight building materials, no 2X4's especially if you only have a 1500.

 

[eDJ_]

In my first Van it had 1/4 inch Masonite flooring with Indoor/Outdoor nylon carpet over that.  This carpet had a black foam backing and did a nice job of deadening the sound.   The flooring was held in place with some screws.  Not many...just enough to keep the flooring from sliding around.  This nylon carpet had a short tight dense pile to it and was perfect.

I've since used 3/8 inch plywood flooring but I would use 1/2 inch plywood if I were to do it all over again. 

I really like outdoor carpet now with the foam backing to use for carpeting a Van.  Never had mold or mildew 
problems with it either.  I did not glue it to the flooring as the bed, kitchenette, ice chest etc held it in place. 

I know you are only asking about solid subflooring.........but you'll soon realize how the carpet makes it feel like a home.

 

[B and C]

I use rubber backed rugs in my van. Easy to clean; take them outside to shake and pound the dirt out.