Small cracks can develop in wooden stairs over time. While these cracks will not cause an unsafe stairway, it is important to repair them to maintain the appearance of your home. Also, a small crack could weaken your stairs by exposing the inner wood to moisture, dirt and other debris. Cracks can be repaired using a wood filler. Wood fillers come in a wide variety of stain colours so that you can select one for your wood species and wood finish.
Apply a small amount of filler to the end of a putty knife. Drag the putty knife across the crack in the stair to fill it in slightly above the surface of the step. Allow the filler to dry for 24 hours.
Sand the filler with a fine-grit sanding pad in the same direction as the wood grain in the stair until it is flush with the surface of the wood.
Wipe off the sanded area with a tack cloth to create a clean surface for the touch-up finish.
Paint over the filled in area with a small paintbrush using a matching wood finish. Allow the finish to dry for four hours and apply a second coat.
Many hardware stores can custom-match wood fillers. Keep this in mind if you have difficulty finding a wood filler that matches your stairs.
Wear eye protection when sanding wood.