How to Finish Interior Stairs

Vacuum the wooden stairs with a vacuum’s bristle attachment. Remove all debris from the stairs in preparation for sanding.

Rubbing 100-grit sandpaper over each stair smoothes rough edges, removes scratches and other impurities on the wood. Follow the wood’s natural grain lines when sanding.

Sanding the stairs with 220-grit sandpaper removes loose wood fibers and any scratches produced by the 100-grit sandpaper. Rub along the wood’s grain lines.

Vacuum each stair thoroughly with the bristle attachment. Remove all sandpaper dust from the wood stairs.

Open nearby windows and turn on ceiling fans for extra ventilation. Cover any surfaces surrounding the stairs with drop cloths, and then put on disposable gloves. Make sure the interior temperature is at least 65-degrees Fahrenheit.

Stir oil-based, prestain conditioner with a wooden stir stick. Evenly apply the prestain conditioner to the wood with a natural bristle brush. Brush each stroke of conditioner along the wood’s grain, focusing on one stair at a time.

Let the wooden stairs dry for 24 hours after coating them with the prestain conditioner.

Stir oil-based stain thoroughly with another wooden stir stick. Using a clean, natural-bristle brush, apply the stain liberally to the top wooden stair using smooth, even strokes along the grain lines. Let the stain absorb into the wood for five minutes. Focus on just one stair at a time.

Wipe the excess stain off the stair with a dry cotton cloth. Follow the wood’s grain lines. Folding the cloth after each stroke prevents wiping stain back onto the stair.

Apply the stain to the remaining stairs, and then wipe off the excess using fresh cotton cloths. Focus on one stair at a time, using the previous staining techniques.

Let the stained wooden stairs dry for 24 hours before applying the second coat or varnish.

Apply another coat of stain to the stairs for a richer color. Stain the stairs using the previous application techniques. Otherwise, proceed to varnish the stairs.

Stir polyurethane varnish thoroughly with another wooden stir stick. Using a clean, natural-bristle brush, apply a thin coat of polyurethane to the stairs using smooth, even strokes along the grain lines. Use about 1 quart of polyurethane per 125 square feet of stairs.

Let the first coat of polyurethane dry for 24 hours before sanding and applying the second coat.

Sanding the stairs with 220-grit sandpaper ensures proper adhesion of the second polyurethane coat. Rub along the wood’s grain lines.

Vacuum each stair thoroughly with the bristle attachment. Remove all sandpaper dust from the wood stairs.

Apply another coat of polyurethane to the stairs to achieve greater durability and wear resistance. Coat the stairs using the previous application techniques.

Let the newly finished stairs dry for 72 hours before walking on them.