Do you think sanding will be able to take out these water marks, or do the boards need to be replaced? The water damage is old (prior to the previous owner, so at least 12 years) and the floor is possibly heart pine (definitely soft). I plan to sand & refinish the whole 2nd floor.
Thanks!
If it were me, I would get a chisel and knock out just one flooring strip. Preferably one of the most damaged strips, and preferably from the edge like under the quarter round. Pull it up and actually test sanding it with an orbital or even just by hand. See how much material you need to remove and consider the final thickness of the flooring - if it's already had three or four rounds of sanding and you're down to the tongues and grooves, it's time for a new floor! If you decide to move forward with a sanding, you can just apply a poly construction adhesive and lay it back down (it will be annoying to remove when it finally is time for a new floor, so others may disagree) or you can face nail it back and try to use a wax filler over the nailheads.
