Underside floor blunder

[JoostD]

Hi all,

I ordered my wood for my build. I received it and made a blunder for the ply on the underside of the floor, it’s prefinished with a thick layer of white paint
Can I use a exterior grade paint to finish it (I have a can of pu coat/paint)? Or should I try sanding it off (and epoxy it) or buy a new unfinished ply…

Any ideas are greatly appreciated!

[TimC]

... it’s prefinished with a thick layer of white paint
...

I'm just wondering if this "pre-finished" plywood might be OSB siding. If so, I wouldn't use it, but, there are some folks who have and had little problems with OSB in the short term. "Short term" is the operative phrase. Long term it just won't perform like a good exterior ply. Of course if it is some other plywood layup it may be ok. Better talk to the lumber yard and find out what it is intended for.

On another note... I've never had any issues with water intrusion through the floor. If you looked under my first TD all you see is "Black Jack" (roofing tar) spread on a 1/2" sheet of ply, no seams since I used 5x8 sheet. Other than a little dust there is no change in my seven year old TD's underside. I don't live in a wet or humid climate so take that into consideration as well.

[JoostD]

Thanks for your post!
It's wpb exterior grade okoume ply no osb. So it's really good stuff, and a bit of a waste to ditch it.. :/

[tony.latham]

it’s prefinished with a thick layer of white paint

Are you sure it's paint? Or is it a layer of Melamine? Melamine is more or less Formica, I believe. My concern would be water getting in from the side plies and not drying out, so I'd make damn sure to seal the edges well.

Tony

[JoostD]

I'll check to make sure. But melamine in the Netherlands is usually partical board of something like it usually not ply. It looks like paint not like a film or plastic laminate. But I'll check to make sure. I could try to paint a small patch to see how it reacts.

[Tom&Shelly]

Is it primer? Seems strange to have something like that pre-painted, but maybe pre-primed if the intent is to use it with a side exposed and later painted to the desired color.

Products available in the US and Europe sometimes are so different it is surprising.

Tom

[JoostD]

Yes it should be primer. Pre primed is probably the better English term sorry
Would a good quality exterior paint work to seal the underside in that case?

[Tom&Shelly]

Yes it should be primer. Pre primed is probably the better English term sorry
Would a good quality exterior paint work to seal the underside in that case?

I'd think it would work really well. Seal the edges as Tony says. As others have said, the bottom of a teardrop is a surprisingly benign environment and I'd think a good quality paint down there would be fine.

Tom

[JoostD]

Thanks for the help everyone! That saves me a lot of time!