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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 & GUARDSD23ceiling / stair above6'-8" MINheadroom, plumb from nosing36" MINguard height4" SPHERE MUST NOT PASSGUARD REQUIRED WHERE DROP > 30"measured within 36" horizontally (§R312.1.1)PLAN — STAIR WIDTH36" MIN CLEARNOTES · IRC 2021 §R311.7 / §R312• Width 36" min above handrail; 31½" at/below one rail, 27" two rails• Risers 7¾" max · treads 10" min (§R311.7.5 — see D3, IRC view)• Handrail 34–38" · guards on open sides of stairs ≥ 34" (§R312.1.2)• Stair guard triangle: 6" sphere limit at riser/tread/rail openingNOT TO SCALE
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.
Sections cite the 2021 International Residential Code and 2023 National Electrical Code as model standards. This is BuildSpec’s own summary — not ICC or NFPA text; read the authoritative language at codes.iccsafe.org. 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 →