How to treat a Subfloor?

[Aubrey0418]

Hello, I am new here so I hope I'm doing this right. My husband and I bought a 1968 frolic 16ft camper which basically needs everything replaced. YouTube and Google have pretty much all of the answers to our build except I'm having a hard time finding information on flooring.
We have to replace the entire floor.
We bought a tongue and groove subfloor ( not marine grade) and wanted to know how to treat it and what exactly to use. We are young and inexperienced so product names are greatly appreciated. I've read some people say to seal it but with what? We will be putting vinyl flooring on top of the Subloor. Underneath it will be insulation and then an exterior grade plywood as the base. The exterior plywood will be exposed to weather, should we seal this too or leave it open to "breathe" when it gets wet?

[GrandpaKip]

Marine grade plywood is overkill in my opinion. Exterior AC plywood would work just as well, is less expensive and easier to find. Not necessary to seal it, either.
I would use foam board for insulation if you think it’s necessary. Since we don’t camp in the cold, I would skip it.
Coroplast, a corrugated plastic sheet, can be used to enclose the underbelly.

[pianotuna]

It may be worth while to go on one of the factory tours--to ask questions about how RV's are built.

[Aubrey0418]

Thank you so so much! It seems like such a simple answer but I've had an incredibly hard time finding information and there's a lot of misinformation out there too. Really appreciate the responses. We'll be going out to buy the marine grade plywood for sure

[Grit_dog]

No, you got it right.
The flooring you put on top of the framing (under the vinyl floor) is the sub floor. As it should not get wet from the elements at all, does not need to be marine grade or treated or anything of the sort. I wouldn’t use OSB as future leaks from plumbing could destroy OSB rather quickly.
By tongue and groove, presume you mean t&g plywood? Tng wood planks might work as well, but more considerations.
The underbelly or skin under the insulation and framing should be marine grade or painted (including the ends) as this sees all the road spray traveling in the rain.
I wouldn’t use wood down there at all. Except maybe cheaper to use 1/4” plywood and paint. Plastic sheeting, filon, bathroom tub surround sheeting, would be more preferable. Not only for moisture intrusion resistance, but you don’t need any “strength” down there. Just something to cover up the insulation. Lighter weight the better.
Good luck with the project!

[Aubrey0418]

Okay I think I'm getting my terminology confused. Is the subfloor what the vinyl (or finished flooring) attaches to, or is it the base which is exposed on the outside of the Camper?

[pianotuna]

I would strongly suggest marine grade materials for the repair. Return what you purchased to the store.

I would lean towards tearing down right to the skin and installing marine plywood as the sub floor.

On top, I'd use one of the non tongue in groove plastic (thick version) floors.

Consider adding a heated floor.

So, make a sandwich:

finish floor (thick plastic NOT tongue in groove)
floor heating
marine plywood
insulation (silver foil)
seal at edges with great stuff or similar foam.

This is a job that will only be done once. Do not skimp on materials cost.