1. ATTENTION returning members. If you are coming here from the old forum for the first time, you will need to reset you password. However, we had an email problem getting password reset links set out to a lot of the email addresses. That problem is temporarily rectified but IF you still have an issue, email me direct at info@thebuildingcodeforum.com and I will give you a temporary password.
    Dismiss Notice
  2. Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by clicking here: Upgrades
    Dismiss Notice

Spiral Staircase, R-3

Discussion in 'California' started by freerangequark, Sep 29, 2018.

  1. freerangequark

    freerangequark Registered User

    Joined:
    Sep 29, 2018
    Messages:
    4
    Likes Received:
    0
    I am working with a designer who said he was pretty sure that the tread width on a spiral staircase would have to be 36" wide if it is the sole means of egress from the second story of an R-3, single family home.

    Location: Cameron Park, Eldorado County, California

    REF: Referencing the 2016 California Building Code which adopts with amendments from the International Building Code 2015 (IBC 2015)



    My research has led to me to conclude that it would be permitted.

    Here is a summary of what I found. I have also provided a copy of the applicable code with pertinent items bold and/or underlined.


    1. This structure is to be an R-3 occupancy which also meets the definition of a dwelling.

    2. One means of egress is required per Section 1006.1, Exemption 1.

    3. Throughout section 1011, spiral staircases requirements fall under exceptions for construction standards.

    4. Staircase Width and Capacity Standards found in 1011.2 normally call for a 36” width, however spiral staircases are exempt from this per exemption 2 and permit a 26” width tread

    5. Section 1011.10 pertains exclusively to Spiral stairways.

    Spiral stairways are permitted to be used as a component in the means of egress only within dwelling units or from a space not more than 250 square feet (23 m2) in area and serving not more than five occupants, or from technical production areas in accordance with Section 410.6.

    A spiral stairway shall have a 71/2-inch (191 mm) minimum clear tread depth at a point 12 inches (305 mm) from the narrow edge. The risers shall be sufficient to provide a headroom of 78 inches (1981 mm) minimum, but riser height shall not be more than 91/2 inches (241 mm). The minimum stairway clear width at and below the handrail shall be 26 inches (660 mm).


    Therefore, spiral stairs are permitted as the sole means of egress in an R-3 dwelling as long as the standards specifically for spiral stairs and all other applicable sections of Chapter 10 Means of Egress are met.


    [​IMG]

    Code compliance can be achieved with a 60” diameter spiral stairway.

    A 10’ above finished floor height rise can be achieved in 11 Steps / 12 Risers.

    30 degree steps per code = 12 steps per 360 degrees = 330 degrees of rotation.



    Please let me know if I am not understanding the code correctly.

    Thank you,
    Glenn
     
  2. RCT

    RCT Registered User

    Joined:
    Dec 5, 2018
    Messages:
    4
    Likes Received:
    2
    Glenn,

    Pretty sure you already got your answer on this, however there is an incorrect note on your posting. Spirals have a riser restriction of 9-1/2" maximum riser which you posted.

    However, I underlined your note on the 10ft total rise with your note of 12 risers in the flight. The 10ft total rise does not comply with 12 risers, 12 risers = 10", you would need 12 steps with 13 risers to meet the 9.5" riser requirement .

    TBZ
     
  3. freerangequark

    freerangequark Registered User

    Joined:
    Sep 29, 2018
    Messages:
    4
    Likes Received:
    0
    TBZ,

    Thanks for the reply... good catch!

    I actually have quotes now for two stairs which have 13 steps and 14 risers (8.6" each). They were able to get the extra step in there and maintain head clearance by using an angled deck at the top.

    Thanks,
    Glenn
     

Share This Page