Q: Our house was built in 1900. We have wood floors under the carpet. I would like to refinish them, but there is no subfloor. The cost is what I am worried about. I have been told that I need to put a subfloor on top of the wood and then put down a hardwood floor.
A: It can be possible to sand the softwood subfloor. I’ve done plenty and am in the midst of one at the moment. It depends on the condition of that floor. If it has multiple coats of paint you would likely be facing a lead issue.
Or, you can screw 3/8 plywood over that which provides a nice stable surface to install a new floor over. You can install directly to the softwood if it is in good condition, reasonably flat; however, if it is tongue and groove pine then it is running across the joists, which is the same direction you new floor would run. So, in that scenario you should install plywood to get a really stable floor.