How do I Build a Wooden Stair Rail on Spiral Stairs?

Building the Form

• 1

  Cut a length of box steel two inches longer than the radius of the spiral stair. Measure one inch from either end and make a mark. Clamp the metal trammel point at one mark and the pencil insert at the other.

• 2

  Screw two pieces of 4-by-8-foot plywood to the floor. Measure 4 feet along the seam between the two and make a center mark. Ask an assistant to hold the metal trammel point at center, while you use the pencil end to draw a circle with a radius equal to that of the stairs.

• 3

  Use a large protractor and a pencil to divide the circle into 40-degree sections. Repeat the operation with two more pieces of plywood.

• 4

  Cut out the four plywood semicircles on a band saw. Cut out the 40-degree sections.

• 5

  Glue and clamp the pie pieces together, so that they make a single pie piece, 13 1/2-inches high. Make sure that all the edges are flush. This is the form for the rail sections.

• 6

  Measure 3/4 inches from the top and bottom of the form. Place the bottom edge of a piece of flexible plastic tubing at the lower mark. Wrap the tubing around the curve until the bottom of the other end is even with the upper mark. Ask your assistant to draw a line on the form, along the bottom of the tubing.

The Handrail

• 7

  Determine the circumference of the spiral stair by multiplying pi by the diameter. Divide this number by nine in order to get the approximate length for the railing sections.

• 8

  Cut 10 pieces of 2-by-2 lumber to the section length you determined. Place them in the steam box, and wait until they bend easily. The steam penetrates relatively slowly, so this process can take several hours, depending on the lumber selection.

• 9

  Remove the first section of railing from the steam box and clamp one end at the edge of the curved form, aligned at the bottom with the lower boundary mark. Continue to bend and clamp the wood around the form, following the guideline between the two points. When the entire piece is clamped, allow it to dry for six to eight hours, or until it is no longer damp to the touch.

• 10

  Remove the dried railing section from the form. Clamp the next section. Take the first section to the stair and install it while the second section dries. Center the railing section over the balusters. Mark the location of each baluster underneath the railing. Drill holes for the balusters in the bottom of the railing, using the marks. Glue the holes, and slide the rail over the balusters' upper ends.

• 11

  Drill a 3/4-inch hole in the center of the upper end of the first railing section. Glue the hole. Insert a 3/4-inch dowel. Drill a 3/4-inch hole in the bottom end of the second railing section. Glue the inside. Slide the section over the dowel to join the two pieces. Continue joining sections and attaching them to balusters until you reach the top of the stair. Sand, stain, and seal the finished handrail.