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Treads WS-4 and WA-4 Tread CA Balusters Railings Sizes Design Options and Ordering
Sizes Welded stairs are available in diameters from 3'6" to 8' in 6" increments. Metric stair sizes range from 1,1 meters to 2,5 meters in 20 cm increments. Cast stairs are available in diameters from 3'6" to 5'0" in 6" increments (1,1 meters to 1,5 meters). A 4' diameter is generally considered the minimum comfortable diameter, but larger diameters will allow greater ease in carrying bundles, trays, etc., up and down. In planning space requirements bear in mind that an opening two inches larger than the diameter of the stair will give a minimum of 1" clearance on the handrail where it passes through the opening.

Spiral stairways with diameters of five feet or more currently comply with most building codes. Diamond plate and radial grating treads comply with OSHA requirements when the stair is used as a second means of access. In all cases, however, it is the responsibility of the installer to determine whether spiral stairs conform with local codes and regulations.

For adequate headroom, the following riser height and tread degrees should be maintained:

Min. Riser Height Tread degree Min. diameter
8 1/2" 30º 3'6"
8" 28º  4'6"
7" 22 1/2º 5'6"