How tall does a guardrail (guard) need to be?
IRC §R312.1model code
Guards must be at least 36 inches high (IRC R312.1.2).
Guards are required where a walking surface is more than 30 inches above the floor or grade below, and they must be at least 36 inches (914 mm) high.
Openings in required guards generally must not allow a 4-inch sphere to pass through (R312.1.3).
Need this scoped to your jurisdiction?
Adopted edition and local amendments vary by city and county. Ask Donnie checks your jurisdiction and cites the exact adopted section.
Ask Donnie →General information based on the International Residential Code (a model code). This is AI assistance to verify — not legal advice. Confirm the adopted edition and any local amendments with your local building department (AHJ) and a licensed professional before you build.