I used a rolling desk chair without a protective mat for a long time. We started sanding the floor with 40 grit sandpaper, but the damaged area still rough and has very dark veins. We decided to sand again with even courser paper. Very small room (10x10) and we are using orbital hand-sanders. Any suggestions or tips?
I'm assuming you've got real hardwood flooring because you'd be asking about how to repair your laminate flooring because 40 grit would have gone through the very thin surface layer already.
So long as you've got enough thickness in the flooring, you'll eventually get rid of the scratches, but you may have to do quite a bit more sanding than "feels" right. If you have a floor register in the room, pull it out and look at how thick the flooring is there, you'll likely be surprised at how thick flooring is (if it's an older home).
Go rent a flooring sander and purchase a couple of belts for it.
- The amount you spend on the rental will be significantly less than the bill for your time - how much do you make an hour at work - bill your sanding time at the same rate, you'll be shocked!
- You'll also get significantly better results because you're actually using a tool designed for sanding floors. Your little hand-held RO sander is making dips in the floor - the (relatively) huge flooring sander will even the effort over a large area and keep it basically flat.
- You may need the RO sander to reach into the corners and edges where the floor sander can't reach, so don't toss it in the bin.