Problems with wood floors can generally be associated with the nail heads not setting below the floor level, and the shoe molding not being removed. To repair a wood floor, it will first need to be sanded. However, before you start sanding, you need to look at the floor carefully to see if there are any broken pieces needing to be replaced or any nail heads showing. If you see nail heads exposed, countersink them using a nail set and hammer.
The shoe molding needs to be removed gently so you can reuse it. Sweep and vacuum the floor to remove any lose debris. Most importantly, before sanding, make sure you have sealed off the room with heavy-duty plastic. Dust will be created and if the rest of the house is not closed off from the room being sanded, everything will be covered with dust. To secure the plastic, use strong tape around the edges.
If you have floorboards that squeak, you can insert a shim from underneath the floor, between the floor joist and the location of the squeaking. You might even try using a hammer and a 2x4 board wrapped in a soft material such as a towel and tapping the area. Another option is to use lubricant like graphite, talcum powder, mineral oil, wood dough, or floor oil, placing it between the boards.
If you find that none of the above methods work, drill a small pilot hole through the squeaking board and nail it from above using a finishing nail. Next, countersink the nail and fill the hole with wood dough. This is also an excellent method for fixing warped or cupped floorboards. If your floor joists are exposed from underneath, a pilot hole can be drilled up through the floor and the sub-flooring, going into the squeaky board �-inch. Using a drill bit stop is the best way to ensure you do not drill through the actual surface of the floor.
If your floor were severely damaged from moisture, repairing would be impractical. In this case, you should sand the floor so it is level. Next, using a drum sander and a rougher grade of sandpaper, make diagonal passes, going across the warped or cupped boards until smooth and even. Once corrected, you will go back over the floor by working with the wood grain so unsightly lines are not seen.
Wood floors that have been marred most often need to be replaced. In this case, the boards would have to be cut and chiseled out and then replaced. Adjust your circular saw's blade to match the thickness of the damaged board. This will prevent the sub-floor from being cut. Taking a hammer, chisels, and pry bar, remove the bad board, being careful not to damage any adjacent boards. Cut the new board the identical length and remove the tongue so it can fit nicely where the old board was before. Using �-inch beads of sub-floor adhesive to the bottom of the new board, you will gently slide it into the opening. The last step is to pre-drill a few pilot holes through the replaced board, going down into the sub-floor. Using finishing nails, nail the board into place, countersink the nails, and fill the hole with wood dough. While repairing wood floors does take time and effort, the result will be a gorgeous floor.