Long stairways present a challenge when installing a wooden handrail. If the stairway is longer than the longest available length of handrail, two sections of handrail must be joined together. Lengths of wood are joined together using a scarf joint. The ends of the handrail that form the joint are cut at a 45-degree angle and placed together so that they form a straight, continuous length of board. Scarf joints are strong and help conceal the joint better than a basic butt joint, which makes it the ideal joint for a handrail application.
Measure to find the length of the stairway to determine the required length for the stair handrail.
Cut a 45-degree angle on one end of each handrail, using a mitre saw, so that the two lengths combine to form a straight length of handrail. Adjust the saw to cut a 45-degree angle slanted to the left on one length and a 45-degree angle slanted toward the right on the second length.
Apply wood glue to the mitred cuts on the two lengths of handrail.
Join the two lengths together and clamp them in place. Allow the glue to dry overnight and remove the clamps.
Sand the joints with fine-grit sandpaper until the joint is completely smooth. Always sand with the grain of the wood.
Measure the joined handrail and mark it to the length required for the stairway. Cut the handrail to length using a mitre saw.
Apply a wood finish with a paintbrush. Allow the finish to dry at least four hours before handling and at least 72 hours before installing the handrail.
Place a mounting bracket as near to the joint as possible when installing the handrail to provide additional support.