Spiral Staircase Code Requirements

The most important thing Precision Pine customers need to know about building codes is this:  Before manufacturing your spiral stair kit, we will check to see if local building codes will govern the installation. If so, we prefer to contact the local inspector either directly or through you to assure that the installation will meet local code requirements.

Regardless of the exact wording of building codes, the local inspector will be the final authority on the interpretation of code requirements and what or when allowances can be made. It is best to include the local inspector before installation begins.

National codes have similar requirements and are listed below.

  1. Maximum rise, the vertical distance between treads: 9-1/2″ (this is higher than the maximum rise for a straight stair—usually 7-3/4” or so– because you have to go down a spiral stair more steeply to gain sufficient headroom under the top landing).
  2. Minimum head clearance above any tread or the landing: 78″.
  3. Minimum tread width: Treads must be at least 7-1/2″ wide at a point 12″ out from the center column.  This means that 7-1/2″ of the tread is clear of the leading edge of the tread or landing above.
  4. Minimum width of clear passageway: At least 26″ from the INSIDE of the spiral handrail to the outside of the center column.  This is the strictest interpretation of the code–some building inspectors will allow the 26″ width to be measured OUTSIDE the handrail.
  5. Baluster spacing: Most codes require a space of no more than 4″ between balusters.
  6. Minimum opening between treads: Some codes require no more than 4″.  Most spiral stairs have greater than 4″ clear space beneath the treads.  Precision Pine supplies additional parts when this rule must be met.