B
HomeLibrariesCode AISearchProjectsBookmarksAddress
FeedbackHelp Desk
Libraries
Estimate & calculate
CalculatorsChecklists
PricingLog in
Home / Code Guides / Deck Stairs

Deck Stair Requirements — Risers, Treads, Guards & Handrails

Deck stairs fail inspections more than almost any other part of a deck, usually over riser consistency and handrail grip. The dimensional rules come from the general stair section R311.7 — the deck section R507 handles the structure the stairs land on and hang from.

RESIDENTIAL STAIR — HEADROOM, WIDTH AND GUARDSD23ceiling or floor above4" SPHEREmust not pass6'-8" MIN34–38"7¾" MAX10" MIN36" MINguard> 30" dropguard requiredPLAN — STAIR WIDTH36" MINclear widthNOTES · IRC 2021 §R311.7 / §R312.1Width: 36" MIN above the handrail; 31½" MIN with a handrail on one side;27" MIN with handrails on both sides (§R311.7.1).Guards on open sides of stairs: 34" MIN from the nosing line; openings4⅜" sphere, triangle 6" (§R312.1.2, §R312.1.3).Guard required > 30" drop, within 36" of the edge (§R312.1.1).Dashed line: line of nosings. Stair, headroom and guard heights drawn to scale at the limits.STAIR AND GUARDS · IRC 2021 §R311.7.1 · §R311.7.2 · §R311.7.5 · §R311.7.8.1 · §R312.1
Residential stairs and guards — IRC 2021 R311.7 / R312.Open full diagram →
RequirementModel Code StandardSection
WidthStairways must be at least 36 inches wide above the handrail height and below the required headroomIRC R311.7.1
Risers and treadsRisers can be no more than 7-3/4 inches tall, treads no less than 10 inches deep, and the largest riser or tread in a flight cannot exceed the smallest by more than 3/8 inchIRC R311.7.5.1, R311.7.5.2
HandrailsA graspable handrail is required on at least one side of any flight with four or more risers, set 34 to 38 inches above the nosings, continuous for the full flight, with grip size meeting the code’s Type I or Type II profilesIRC R311.7.8
GuardsOpen sides of stairs more than 30 inches above grade need guards at least 34 inches high measured from the nosings; openings on the stair sides must reject a 4-3/8-inch sphere, and the triangle at the tread, riser, and bottom rail a 6-inch sphereIRC R312.1.1, R312.1.2, R312.1.3
LandingsA landing or floor is required at the top and bottom of the stairway, at least as wide as the stair and 36 inches deep in the direction of travelIRC R311.7.6
IlluminationExterior stairways need an artificial light source at the top landingIRC R303.8
Structural supportStringers must bear on adequate footings or hardware at the bottom and be positively attached to the deck framing at the top — not just nailed to the rimIRC R507 (framing and connections)

Worth knowing

  • The IRC has no stringer span table. The AWC’s DCA 6 deck guide — adopted as gospel by many jurisdictions — limits cut 2x12 stringers to about a 6-foot horizontal span and solid stringers to about 13 feet 3 inches; add a middle stringer or a brace beyond that.
  • Riser consistency is measured over the whole flight, including the bottom step. Pouring a patio after the stairs are built is a classic way to create an illegal short bottom riser.
  • Open risers are allowed, but where the stair is more than 30 inches above grade the opening cannot pass a 4-inch sphere — a strip of trim under each tread usually solves it.
  • A 2x6 top rail is not a handrail. Inspectors want a graspable profile — round 1-1/4 to 2 inches, or an approved shaped profile — mounted on the guard.

Common questions

What does the code say about width for Deck Stairs?

Stairways must be at least 36 inches wide above the handrail height and below the required headroom. (IRC R311.7.1)

What does the code say about risers and treads for Deck Stairs?

Risers can be no more than 7-3/4 inches tall, treads no less than 10 inches deep, and the largest riser or tread in a flight cannot exceed the smallest by more than 3/8 inch. (IRC R311.7.5.1, R311.7.5.2)

What does the code say about handrails for Deck Stairs?

A graspable handrail is required on at least one side of any flight with four or more risers, set 34 to 38 inches above the nosings, continuous for the full flight, with grip size meeting the code’s Type I or Type II profiles. (IRC R311.7.8)

Adopted edition by state

Base-code year from BuildSpec’s adoption records. States often amend the base code, and your city or county may differ, so confirm with your building department.

Related sections and guides

This guide is BuildSpec’s own summary, not code text. It cites the 2021 International Residential Code and the 2023 National Electrical Code as model standards. The IRC 2021 text itself is in the Code Library for signed-in members; BuildSpec publishes no NEC text, which is at nfpa.org.Neither is an adoption record: your state may be on a different edition with amendments — check your jurisdiction page or get an Address Report.
Deck Footings →Deck Ledger →GFCI Protection →Egress Windows →Stairs →Handrails & Guards →