Our first step was to clear everything from the room and start with the edge sander. We started with a 20 grit sandpaper and sanded the entire perimeter or the room. Keep this baby moving, or you will have gouge marks. Don’t worry if you don’t get everything sanded around the edge in the first sweep. Just keep going around the perimeter until all of the finish has been removed!
Do not move onto the next grit of sandpaper until you have used the 20 grit on both the drum sander AND the edge sander!
This is what our floor looked like after we had finished sanding the entire perimeter with the edge sander. See those black stains there? Cat pee. One of the hardest things to remove from wood floors. We actually ended up sanding even more after this photo and almost COMPLETELY removed the cat pee from the wood.