Contact your local building department to determine if a building permit is required. Measure the angle between the treads of the staircase to determine the angle of the railing. Calculate the railing height, ensuring that you use at least the minimum height required by the building code. Draw an accurate sketch showing the existing stairs, the placement of the newel posts and the railing height. From this sketch, you will be able to determine the height of each of the two balustrades on each step.
Cut the top rail to the desired length, ensuring that the ends are angled properly. Cut to size four of the balustrades. Mark out a side view of the staircase with masking tape on the floor of your workspace, and then lay out the top railing and balustrades to the correct angle to test whether the length of the balustrades was determined accurately. Make any necessary adjustments, and cut out the rest of the balustrades to size.
Mark out the location for the newel posts on either the floor or a step. Secure a metal bracket to the floor or step in that location with wood screws. Place each newel post into the metal bracket, and secure into place with wood screws.
Drill a hole slightly smaller in diameter than the size of the dowel into the top and bottom of each balustrade at the center point. Mark out the location of the dowels on each step with a ruler and pencil. Accuracy in the measurements is key to the success of the project.
Drill two holes on the marked spots that are slightly smaller in diameter than the size of the dowel for the balustrades. Install a dowel into each hole on the stairs, apply a small dab of glue around each dowel, and then fit each balustrade onto a dowel.
Attach the top railing to the tops of the balustrades either with wood glue, with dowels, or a combination of the two. Secure railing to the newel posts with a dowel and wood glue.