How to Finish Wood Stairs Between Two Walls

Sand the steps down with medium-grade sandpaper. Suck up the excess dust with a shop vac, then sand the steps again with fine-grade sandpaper. Suck up the excess dust, then wipe the stairs down with a wet rag.

Tape off the walls at the edges where they meet the stairs so you don't get stain on them. If you only plan on staining the treads -- the tops of each step -- tape off the risers -- the fronts of each step, which many people paint white to offset the stain.

Mix the stain thoroughly. Pour the stain in a small bucket. Dip a clean cloth or a paintbrush in the stain, then wipe the excess on the lip of the bucket. Start at the top of the steps and spread the stain over each step with the grain.

Allow the stain to soak into each step for about 30 seconds to 1 minute, then wipe the excess away with a fresh cloth. Repeat this process until you reach the bottom of the stairs. Allow the stain to dry.

Mix the polyurethane by stirring carefully. Avoid shaking the can, as this can create bubbles in the finish. Pour a small amount of polyurethane in a bucket. Dip a foam or lamb's wool applicator in the polyurethane, then lightly slap the applicator against the inside of the bucket to release the excess -- avoid wiping the applicator against the lip of the bucket.

Spread the polyurethane evenly over each step. As with the wood stain, always work with the grain when applying polyurethane. Allow the polyurethane to dry overnight.

Sand each step lightly with very fine-grade sandpaper. Wipe away the dust with a moist cloth. Apply one to three more coats of polyurethane in this fashion.