THOSE "HAUNTING" SPIRAL STAIRS

Julie Harris peers over the edge of an extremely cool
spiral staircase in the Robert Wise-directed film
The Haunting. It's worth seeing even if you're
not in the market for stairs.

Spiral stairs have gained a melodramatic reputation through their appearance in films such as the 1946 film noir thriller The Spiral Staircase and the chilling psychological ghost tale The Haunting (1963).  That alone justifies their use for some purposes—in order to add edgy atmosphere, for example. The intriguing form of a spiral staircase can lend a great deal of sculptural interest to an otherwise humdrum area. But spiral stairs have a practical side as well, especially where space is at a premium.  
    
First, a few definitions for terms that are easily confused:  A true spiral stair has treads radiating from a center post.  A circular stair, on the other hand, has an opening in the middle: it’s basically just a regular stair that curves. A winding stair is a conventional stairway with angled treads where the corner landings would normally be. The last two are not spiral stairs.

Your basic metal spiral stair that's available in kit form.
Treads are typically available in various wood species
or plain or nonskid (checkerplate) steel.

True spiral stairs are ideal for access to lofts or basement areas where a straight staircase would consume too much floor space. While a conventional stair might require around 42 square feet—not counting landings—a spiral can make the same trip in about 25 square feet. This difference could get you out of a planning tight spot, as it has many an architect over the years. However, think twice before using these stairs if there are children or elderly people around—their high riser height and sharp edges can make them hazardous to negotiate. 

Generally, the minimum nominal spiral stair diameter allowed by building codes is 5’.  The maximum riser height can be 9 1/2”—considerably steeper than the 8-inch rise allowed for conventional stairs. However, because spiral stairs are steeper and more dangerous than conventional stairs, buildings codes restrict their use in certain situations—check with your local building department for specifics. The distance between balusters—the vertical pieces in the railing—can be no more than 4”. Floor openings can be either round or square, or the staircase can be entirely freestanding adjacent to an upper floor gallery.

Wood spiral stairs are generally better suited
to traditional home styles. The wood species
and finish can be matched to existing trim.

Metal stairs are available with a variety of tread surface materials including smooth or industrial checker plate steel, hardwood, or a backing material suitable for carpeting. A few manufacturers offer cast-iron stairs, which have a more ornate appearance suitable for Victorian-era homes. Although 5’ is the minimum diameter for egress stairs, diameters as small as 3’-6” are available for use as plant shelves and the like.  

Wood spiral stairs have an even wider range of designs, making them appropriate for both traditional and contemporary home styles. They’re available with ornamental turned balusters or simple dowel-like ones, and a large range of finishes are possible.  

Although top-of-the-line spiral stairs are usually custom-fabricated, many manufacturers offer more economical spiral stair kits in both metal and wood, some starting at less than $1000.  These kits are assembled on site. Some of them require the total rise to be specified before ordering; others can be adjusted to suit varying field conditions.