Metal Spiral Stairs

Spiral stairs are a specialized solution to accessing another story or level. Theaters and equipment mezzanines are the main uses for a spiral stair. A residence in need of a little drama is another use. 
Benefits
Besides being aesthetically cool, spiral stairs have some key benefits. They have a very small footprint, rivaling a ship's ladder. Spiral stairs are extremely functional. None of their structure is excess, everything works together. For the architect there is no detailing to do, just a layout and selection of parts from the manufacturer's standards. Finally, spiral stairs are fun to use - at least for a while.

Limitations
Code issues - the usual prescriptive requirements apply - only different ones; and, most importantly, where you may use a spiral stair is spelled out. A critical issue is that a spiral stair is not treated as a means of egress, except in certain cases. In all others, spiral stairs are considered an incidental stair.
But the cost at about $2,000-$3,000 per vertical linear foot is a major reason for the few spiral stairs that you come in contact with. 
For the designer, the top and bottom orientation is tricky to work out because it is a function of the number of risers, and unlike a typical switchback stair, you might be facing any direction when you arrive at the top. Headroom can be troublesome at landings.
Using a spiral stair makes for a steep climb, almost like a ship's ladder; and descending can give a thrill because straight ahead is open space with a railing that appears to be at ankle level.
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C2010-C - Spiral Stairs

COMMENTS:

• These plans are needed to specify the size and configuration required for the spiral stair 
• These plans require further specifications covering materials, construction and finish.
• Building Codes have an impact on many aspects of a spiral stair.
• A level landing is required at 12' of rise and is equal to three treads.
  
• In a non-functional setting, like a house, be aware of the potential for a modesty issue.
  
• These details should be placed on the Interior Details sheet, the A-400 series of sheets per the National CAD Standards, contrary to the designation shown here.
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