Copper II wood treatment for replacement floor

When building sailboats, we used AC Fir plywood for subfloors. We used spar varnish on all the edges to seal it. I would never use any wood preservative for interior application if it is labeled for exterior use.

Heed the warning. Copper Napth is some really nasty smelling stuff. I have used this to treat cut ends of treated lumber in outdoor projects. One project in particular I did 3 months ago, and I can still smell it when I walk by now.

There is a reason that pressure treated lumber isn't used in interior spaces, it can be toxic and a health hazard. Painting new pressure treated lumber or sheet goods can be problematic as moisture content is high when shipped from the mill to the distribution outlet, i.e. where you buy it.

FWIW, I replaced all the paneling in my RV with Luan sheet goods and a couple pieces of flooring with 5/8" CDX plywood. The plywoods and paneling were coated, both sides and edges, with a flooring finish made for bowling alleys and gym floors. That finish does a good job of sealing the wood, as would any urethane finish or spar varnish.

I acquired the wood finish at my local recycling center. They typically have gallons of paint and finishes that are unused and the cost is perfect-$0.00.

The use of the product SHOULD NOT BE USED IN YOUR RV. The chemical smell will make you sick. I do a lot of repairs, and the best method for protection is use a an epoxy based paint, (KellyMoore). That will seal and not make you sick. You will NEVER get rid of the smell and toxins from those products. Outdoor use only. Hope this helps

I just did a major floor repair(post and pictures will be coming soon)and replaced floor with exterior grade 5/8" plywood. I coated the plywood and the 2x3 joints I needed to replace with Thompsons water seal as added protection. Also replaced fiberglass mat insulation with 2" Styrofoam panels to prevent wicking of moisture from the moisture barrier underneath. Not sure if I would go as far as wood preserver unless you are anticipating major moisture issues

Thanks SidecarFlip, your comments are generalized but welcome.

I intended to coat all plywood surfaces, especially all exposed or cut edges. This particular product says it is intended for use prior to staining but also says it is for surfaces not intended for painting which makes me question adherence characteristics of the treated surface. The plywood underside will be in contact with the polystyrene, likely with some construction adhesive, and I was thinking of vinyl type flooring on top glued down with some leftover proper flooring glue from my kitchen reno.

I agree with the OSB comments from the research I've done which is why I intend to opt for Douglas Fir plywood as my choice.

I would think so long as you don't eat the floor, you'd be fine. PT wood isn't as bad as it used to be, They removed the arsenic from the equation. Think I'd coat the underside (road side) of the plywood with preservative as well.

I find it amazing the builders use OSB for flooring. OSB, when it gets wet, turns to mush and the roadside will get wet.

Again, all about the cheapest materials.

and... OSB is loaded with formalhyde.