How to Finish Stairs

Sand the wood surface of each step in the stairway with your pad sander and heavy sandpaper. Remove all existing finish and vacuum the dust.

Repeat the sanding process with medium sandpaper and then fine sandpaper. Vacuum and the stairs should now be bare, clean and smooth.

Spread wood stain over the top stair using a paintbrush. Lay it on thickly. Let it sit for a minute. Use an old rag to wipe up excess stain.

Repeat the process two steps down on the staircase, so there is an unstained stair between the two stained stairs. Continue working your way down the staircase, staining every other stair. Let the stain dry for 12 hours. Step on only the unstained stairs when you use the staircase as it's drying.

Repeat the process to stain the stairs that weren't previously stained. As you work your way down the staircase, put a small piece of masking tape on each of the steps that was stained the first time, so you'll know which steps you can use as the newly stained steps are drying. Let the stain dry for 12 hours.

Brush polyurethane over the top step with a paintbrush. Apply it in a thin, even layer. Repeat for each alternate stair. Put a piece of masking tape on each stair that isn't glossed, so you'll know which ones you can use. Let the polyurethane set for 12 hours.

Lightly sand the polyurethane by hand with fine sandpaper, dulling the surface. Wipe off the dust. Brush on a second layer of polyurethane, putting it on the same steps as before. Let the stairs dry.

Add a third coat of polyurethane to the stairs in the same manner, dulling the surface first with fine sandpaper. Let it dry for 12 hours.

Apply polyurethane to alternating steps in the same three-coat process as before. Put pieces of tape on the first course of steps so you'll know where you can walk.