Residential Stair Codes

BUILDING CODE DESIGN GUIDE
Written By Kylie Nielson

IRC Code Requirements

(Last updated to 2021)

  • R311.4 Vertical Egress defines where egress stairways are required in a project.

    • You could argue that any additional stairs provided do not have to meet the egress stairways requirements but it is likely to meet some resistance from building officials on the matter.

  • R311.7 Stairways explain R311.7.1through R311.7.8 and R311.7.10. Know why the rest of the sections exist, then review the following

    • R311.7.1 Width min width of a stairway and how to measure

    • R311.7.2 Headroom min clearance req’d and how to measure

    • R311.7.3 Vertical Rise max vert rise on a flight of stairs before a landing or level

    • R311.7.4 Walkline defines walkline for determining winder tread design (curved stairs)

      • Difference between a curved stair and a spiral stair

    • R311.7.5 Stair Treads and Risers Rules for design

      • R311.7.5.1 Riser Height max riser height allowed (Utah is more than other states) and how to measure it.

        • Never design stairs to max riser height allowed to allow for construction tolerances as this is the max allowed after it is constructed.

      • R311.7.5.2 Tread Depth min tread depth allowed and how to measure it.

        • Tread depths can be built exactly so designing them to the code min is fine.

      • R311.7.5.3 Nosings rules for nosings, angled risers, and open riser stairs.

        • Nosings req’d for solid riser stairs that are less than 10 inches in depth.

    • R311.7.6 Landing for Stairways locations and sizing of req’d landings

    • R311.7.7 Stairway Walking Surface flatness requirements of stair walking surfaces

    • R311.7.8 Handrails design rules

      • Include on one side of and for length of stair runs (with no extensions req’d)

      • Height requirements and how to measure

      • Projection

      • Clearance

      • Continuity

      • Grip Size

    • R311.7.9 Illumination stair lighting requirements

    • R311.7.10-12 Special Stairways, Alternating Tread Devices, Ship’s Ladders

      • Rules for Spiral Stairways and other non-typical stair and ladder devices

Other

  • 1003.3.1 Headroom - Protruding Objects requires a barrier be provided where there are head knockers along an egress path.

    • Cane rail and how it provides a solution for this requirement at stairs

    • Other solutions that could meet this requirement


Kylie Nielson
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Commercial Stair Codes