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Code and safety · 6 min read

Railing Height & Spacing: Code Basics

The 36"/42" rule, the 4-inch sphere test, and where guard rails are required at all.

StairSupplies Craftsmen6 min read

Codes vary by state and municipality — always confirm locally. That said, most U.S. residential projects fall under IRC rules.

When a guard is required

Any walking surface more than 30 inches above grade needs a guard rail at least 36 inches tall (42 inches in some states, and typically 42 inches for commercial IBC projects).

The 4-inch sphere rule

No opening in the guard may pass a 4-inch sphere. For cable railing this drives cable spacing (3 inches on center is standard) and proper tension.

Stair rail specifics

  • Handrail height: 34–38 inches above the stair nosing.

  • Graspable profile: 1-1/4" to 2" round, or equivalent.

  • The triangle at the stair/guard/tread junction may pass a 6-inch sphere.