Q: I am installing hardwood on our main level. We have a open staircase and railing. Part of the upper level was carpet. I want to remove pro-board and lino in the rest of the main floor and install hardwood over the OSB that was under the carpet. Can I install hardwood over OSB?
A: The National Wood Flooring Association as I understand it has approved OSB as a surface which can be nailed to. I think it partly would depend on how thick the OSB is. Personally, I would prefer real wooden plywood.
Similar Q: have 5/8, 50 year rating OSB on my main floor. Can I install hardwood flooring on top of it?
A: Not a very good surface to work with.. I don’t like OSB at all and I don’t think I would attempt a 3/4 nail down floor on this unless I also intended to use adhesive. I would be more inclined to screw down 3/8 spruce sheeting on top of it. This sub floor you have won’t do a good job of holding fasteners, aka cleats.