How to Refinish Hardwood Floors

Remove all furniture from the room. Remove shoe molding and baseboards carefully with a pry bar (number them so they go back in the right places). Pull up any floor vents or transition strips. Seal doorways with plastic sheeting and painter's tape to contain dust. Cover HVAC vents with plastic. Set nails below the floor surface with a nail set and hammer so they don't catch the sander.

Start with 36-grit sandpaper on the drum sander. Sand with the grain of the wood, moving at a steady walking pace. Start the sander while it's tilted back (drum off the floor), then slowly lower it to make contact. Never let a running drum sander sit still — it will dig a valley in seconds. Overlap each pass by about 3 inches. This first pass removes the old finish and levels the floor.

The drum sander can't reach within 4-6 inches of the walls. Use the edge sander with 36-grit paper to sand the perimeter, corners, and any areas the drum couldn't reach. Move the edge sander in a sweeping, semi-circular motion. This is the most physically demanding part of the job — take breaks to avoid fatigue and mistakes.

Replace the sandpaper with 60-grit and repeat the entire floor with both the drum and edge sanders. This removes the scratch marks left by the 36-grit. Then do a final pass with 100-grit sandpaper. Each successive grit creates finer scratches that give the finish something to grip. Vacuum thoroughly between each grit change.

Mix wood filler with some of the sanding dust to create a color-matched filler. Press it into any gaps between boards, nail holes, and minor gouges with a putty knife. Let it dry according to the manufacturer's instructions (usually 1-2 hours), then sand flush with 100-grit sandpaper. Vacuum the entire floor again.

Vacuum the entire floor, edges, and corners thoroughly with a shop vacuum. Then go over the entire surface with a tack cloth to pick up any remaining fine dust particles. Any dust left on the floor will be trapped under the finish and visible forever. Also vacuum the walls and any horizontal surfaces where dust has settled — you don't want it falling onto wet finish.

If you want to change the floor color, apply oil-based wood stain with a foam brush or rag, working in 3-4 foot sections. Apply generously with the grain, wait 5-10 minutes (per the stain label), then wipe off the excess with clean rags. Work quickly at board junctions to avoid lap marks. Let the stain dry 24 hours before applying polyurethane.

Stir (never shake) the polyurethane. Using a synthetic floor finish applicator (T-bar) or a high-density foam roller, apply a thin, even coat of polyurethane with the grain. Start at the far corner and work toward the exit door. Maintain a wet edge to prevent lap marks. Apply in long, smooth strokes. The first coat will raise the grain slightly and look rough — that's normal.

After the first coat is fully dry, lightly screen the entire floor with a 120-grit sanding screen on a random orbital sander or pole sander. This knocks down the raised grain and gives the next coat something to bond to. Vacuum and tack cloth again, then apply the second coat. Repeat the screening and application for a third coat. Three coats of poly is the standard for residential floors.

Wait at least 24 hours before walking on the floor in socks (48 hours for shoes). Wait 72 hours before moving furniture back. For oil-based poly, wait a full week for heavy furniture. Reinstall the baseboards and shoe molding using your numbering system. Touch up any nail holes in the trim with wood filler. Stand back and admire your work — you just saved thousands of dollars.