How to Refinish a Top-Nailed Hardwood Floor

Scan the floor carefully for protruding nails and pound each one down with a nail punch and a hammer. Sink the head about 1/8 inch past the surface so the hole will accept filler. Any nails that you miss will be sanded flat by the floor sander, leaving a noticeably flat, shiny surface.

Thin a gallon of latex floor filler that is the same color as the floor with water until it is the consistency of honey. Pour it on the floor and spread it evenly with a rubber grouting float. Work it into all the nail holes, as well as into all the gaps between boards. Let it dry overnight.

Install a 50-grit sanding belt on a flooring drum sander and sand off the filler and the finish coat. In most cases, it's best to run the sander in the same direction as the flooring planks, but if the boards are cupped or uneven, some refinishers run the machine diagonally, and then make a second pass parallel to the boards to remove scratch marks.

Sand the edges and the corners of the floor with a flooring edger, which is a heavy-duty disk sander, using a 50-grit disk. The edger won't reach into tight corners, so you'll have to remove the finish from those places with a floor scraper. Use a pull scraper, and change the blade frequently to keep it sharp.

Vacuum the floor, then change the belt on the drum sander to 80-grit and sand again, going parallel to the flooring boards. Sand the edges with the edger, using an 80-grit disk. Vacuum the floor again and repeat with both machines, this time using 100-grit sandpaper. Use a palm sander and 80-grit sandpaper to touch up the corners where you used the scraper.

Vacuum the floor and wipe it down with a damp rag to remove sanding dust from the grain of the wood. Spread a stain on the floor with a rag, if desired, then use another rag to wipe it off. Let the stain dry overnight.

Apply a clear finish with a floor finish applicator. The best applicator is a foam pad wrapped around a weighted tube which is attached to a long handle. Pour the finish on the floor and then drag the applicator through it, parallel to the plank direction. Let the finish dry for the period specified on the container.

Screen the floor by fitting a 120-grit sanding screen to a floor buffer and running it over the floor. The screen will knock down the grain of the wood and remove bumps. Vacuum the floor and apply another coat of finish. Screen again and apply a third coat if desired.