Check the building codes in your area before doing any work. If you are buying a kit, many companies will not send you the kit until they see a signature from a building inspector.
Begin the stairs from a loft or floor opening for an easier start. Having the stairs against a wall can make it harder to get the turn and headroom right.
Set the stairs so you have enough headroom. The headroom on the top stairs should be 6 feet 6 inches.
Measure the height and diameter of your staircase. The diameter should also include a clearance of at least 2 inches from walls and floor for the handrail.
Calculate your tread height. The width determined for this is the outside of the steps, not the inside.
Select the wood for the staircase.
Cut all the stair risers at once and cut them only 4 inches wide. Anything wider and they will curl and be useless. You will be using multiple pieces of wood to make a single riser. Alternate the wood grains when you assemble the pieces.
Glue the pieces together after sanding the cut marks.
Cut the inner part of the stairs with a band saw to get the circular center. Mount the stair before cutting to keep your radius correct.
Mark where the center pole goes and mount it with a plumb bob. This will keep it from moving side-to-side. The weight of the staircase will be on this pole so it needs to be able to withstand the pressure. The pole will be the same length as the floor-to-floor height measurement for the stairs.
Weld the top and bottom step to the center pole.
Install the rest of the stairs, attaching them to the center pole.
Install the railing. Since this is the hardest part of making the spiral stairs, buying one made specifically for a spiral staircase is the best idea.
- Know that 16 treads is an average size for stairs.
- To determine the riser height, take the diameter and divide it by pi (3.14). This gives you the circumference of the stairs. Divide this number by the 16 treads and this will give you the outside tread width.