On a new build, our subfloor is going to be 18mm plyfloor. I like the idea of painting it with a whitewash and then coating it with polyurethane to keep it as our main floor, rather than covering it with vinyl or laminate planks. Is that a possibility? What are the pros and cons if so? Thanks in advance.
Pro: cheap, and nothing prevents you from putting a real surface on if you find the look does not really appeal after a while.
Cons: Potential for nasty splinters; plywood splinters are miserable. Relatively loud (both to walk on, and acting as a reflector of sound - also loud to the level below if there is living space there).
Pros: I can't think of any.
Cons: You will have gaps and screws showing, it will be extremely hard to clean, plywood will suck up poly faster than a fat guy drinking a milkshake, ditto the whitewash...
Real not to do it are simple. You would have to sand down everything to prevent splinters. Good chance an inspector doesn't even pass it. No way I could get a house passed with exposed subfloor in a lot of areas. Also this will cost you in the long run. All of your trim on the main floor will be installed at plywood height. If you put a real floor other than rolls of vinyl all of your trim will have to be cut or pulled and reinstalled.
Pick up any Dwell issue and you will see plywood floors all over the place. No real cons other than style taste but realize you still need to 'finish' the floor by proper sanding, nail/screw setting and finish.
One potential con is that you can't resand and refinish plywood floors more than once or twice. The top layer is just not thick enough.