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US spiral staircase codes

Before you think about the aesthetics of your spiral stair you need to address the practical issue of building codes. Please contact your local building inspector before you place an order for a spiral stair. There are three national codes that may apply: the CABO (Council of American Building Officials), UBC (Unified Building Code), and BOCA (Building Officials & Code Administrators). The most common specifications result in spirals with the following dimensions/requirements:

Spiral Stair Building Code Compliance

  • Minimum stair diameter of 60" for a metal stair and 64" for a wood stair
  • Tread path between handrail and center column a minimum 26"(660mm)
  • Center tread width, 7 1/2"(190mm) in from the narrow end of the tread d
  • Headroom minimum of 6'6"(1982mm)
  • Riser height cannot exceed 9 1/2"(241mm)
  • Baluster spacing of no more than 4" (to prevent children from sticking their heads between balusters)
  • Minimum height of the handrail of 34" from the tread nosing to the top of the handrail
  • Landing width, 4" longer than the tread path
  • Rail height on the landing, well and balcony rail has a minimum height of 36"(914.4mm)
  • Weight capacity, a minimum of 300 pounds per square foot

Stairways makes every effort to create stairs that will meet or exceed all national codes, but there are often state or even local codes that may supersede the national codes. Codes are frequently tied to the area being accessed; they may be less stringent when stairs lead to an open space such as a loft or cupola, and the square footage of the area be accessed may also make a difference.

Some authorities allow stairs that they warn will not meet code for sole access to a second story, but can be used for auxiliary stairs. If your stair does not have to be built to code specifications, we offer a full line of standard stairs built with 22.5 and 27 degree treads. The stairs can be built in varying diameters. We can also design and build a stair to fit any conditions.


Contact: Katy Hu

Phone: 15112916100

Tel: 86-18934374081

Email: info@whalebuild.com

Add: No. 25, Third Industrial Zone, Caobian, Dali Town, Nanhai District, Foshan City, Guangdong Province, China

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