I love a spiral staircase, especially the design and installation. Spirals come with some heavy restrictions beyond that of a "normal" staircase. First and foremost is the idea that a spiral stair serves as a secondary staircase in a home or business; or it serves as a loft access that does not exceed 400 to 500 square feet (depending on local codes).
Code compliant spirals are rather vague when you consider it is under or applies to the BOCA, UCB, CABO, IRC 2003, IRC 2006, or IFC 2006 codes. One must check with their local building department to get an update on what codes your spiral with fit.
Here is a short list of the most common code factors:
1. Minimum clear walking path of 26 inches. This means that the spiral will be a minimum 5-foot diameter
2. Each tread will have a minimum of 7-1/2 inch tread depth and 12 inches from the narrow edge.
3. The riser height (from the top one tread to the next) shall not be more than 9-1/2 inches in height.
4. The staircase must maintain a minimum headroom of 6 foot 6 inches.
5. The balusters (spindles) shall be installed so that a 4 inch sphere cannot pass through. A couple code agencies permit up to 4-3/8".
6. The stairway must have at least one handrail on the wide edge of the tread.
7. Handrail height, measured vertically from the nose of the tread, shall not be less than 34 inches and not more than 38 inches.
Some define a spiral as a stair which winds around a central pole. That doesn't always hold true. Five years ago a homeowner was given the okay through his building department to install a ladder or spiral accessing his 400 square foot library loft. They did not want the traditional spiral, but rather the look of a free standing staircase with glue-laminated stringers. This would require an inside and outside handrail, the inside being a 6 inch radius. We got the classification of a ladder and built a complete free standing spiral stair with enclosed risers, inside and outside skirts. In essence, a spiral can be creative a creative design only housed by your imagination.
Here's a fun fact: Spiral stairs in medieval times were made of stone and were installed in a spiral down right. This put attacking swordsmen at a disadvantage who were generally right handed and served as defensive in design and structure
Joseph Swallow has been with Westfire Manufacturing since 1994 and now serves as the company's CEO. Prior to Westfire, Swallow worked in Southern California and Las Vegas as the primary sales representative for Hardwood Creations, a company which he had founded in his garage in 1981. Westfire Stair Parts are available anywhere in North America and can be purchased by calling Westfire toll free 1.800.692.6996 or by visiting their website http://www.westfirestairparts.com
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