How Do I Replace a Wooden Banister Slat on Stairs?

Remove the broken banister slat. If the broken slat, also called a spindle, is hanging free, pry the top and bottom away from the banister with a pry bar. If the spindle is partially broken, saw it in half with a small saw like a coping saw before removing.

Purchase a replacement spindle. Spindles vary widely in their shape, size, and material, but most kinds can be purchased or duplicated to match the original spindle. It is important to match the shape, size, and material exactly. Bringing the broken spindle to a hardware or woodworking store will help find a match.

Measure and mark the angle of the banister on the new spindle.

Cut the angle measured in Step 3 from the top and bottom of the replacement spindle. This will ensure the spindle can slide into place between the handrail and the stair.

Match the finish of the spindle with the original using stain or paint. Allow the spindle to completely dry according to manufacturer instructions.

Set the spindle in the place where the broken spindle was removed. Some banisters will have holes cut into the rail and stair which you can slide the spindle into and will hold it in place. If the banister doesn't have holes, just support the spindle until you can nail it firmly in place.

Hammer a nail through the base of the spindle into the stair at a 45-degree angle. Hammer another nail the same way through the opposite side.

Sink the nails a few millimeters below the surface of the spindle with a nail set. Make sure the nail set is the correct size to fit snugly on the head of the nails you are using.

Paint or apply varnish to any marks or nicks incurred during the installation.