So you are considering a spiral stair for your project. Great, but before you start, there are a number of things you need to consider to make sure a spiral staircase is right for you. One of the first things you need to consider is whether or not you need to your spiral staircase to meet local building code. Here at Salter Spiral Stair we have stairs that meet all national building codes, but we always recommend checking with your local building inspector to see if there are any additions that your specific city or township has added regarding spirals. Starting a relationship with your local building inspector is always a good idea, even if you are doing just minor modifications or a large new construction project more help.
This is a brief list of some of the requirements which apply to the BOCA Code, UBC Code, IRC Code, and IFC codes.
Minimum clear walking path of 26 inches. A 5-foot diameter or larger stair will provide this width.
Each tread will have a minimum of 7 1/2 inch tread depth at 12 inches from the narrow edge.
All treads will be identical.
The tread rise shall not be more than 9 1/2 inches high.
Minimum headroom of 6 foot 6 inches shall be provided, measuring plumb from the edge of the platform down to the tread below.
Landing width shall not be less than the required width of the stairway. Minimum spiral stair tread width is 26 inches.
Stair balusters shall be spaced so a 4-inch object cannot pass between.
On our website we have a visual representation of national building codes for all Salter stairs. On the other hand if you do not need to meet any building code requirements, then there are numerous options in terms of the diameter of the stair and other options which are not required, again Salter has a number of different spiral stair packages to fit your needs.
After code requirements are settled you then need to think of the budget for this stair and which options as well as materials you would like. What diameter (minimum diameter is 5′ for code compliancy), options like wooden upgrades or powder coating, going through a floor or off a loft, enclosure railing for the top of the stair, and the list goes on. Additionally you need to consider a different set of options for exterior projects. I recommend considering powder coated aluminum for durability and beauty, but another great option is galvanized steel. Then you need to consider non-slip diamond plate treads or perhaps the same material as your deck so it matches.