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California Guard Height: 42 Inches Under the CRC

On decks, porches and landings California wants guards at least 42 inches tall, six inches more than the model IRC. Here are the rules and the stair exceptions.

CRC 2025 Clause CA CRC R321 Clause IRC 2024 R321

The requirement

On a deck, porch or landing in California, a guard must be at least 42 inches (1067 mm) tall. The model IRC asks for 36 inches. You need a guard where the drop is more than 30 inches. Open stair sides follow a lower figure. The rule is CRC Section R321.1.2.

A guard is the barrier along an open edge. It stops a fall off a deck, a porch or a stair. That taller height is the one big change the state makes here.

When you need one. Look at the drop below the edge. Measure from the walking surface to the floor or the ground below. If that drop is more than 30 inches, you need a guard. You run that check at any point within 36 inches of the open edge (R321.1.1).

The rule covers floors, decks, stairs, ramps and landings. Insect screen does not count as a guard. That trigger matches the model IRC word for word.

How you measure the height. On a flat surface, measure straight up from the floor. On a stair, measure up from the line that joins the stair nosings. The top of the guard must reach 42 inches above that line (R321.1.2).

The stair exceptions. Two of them apply on the open side of a stair. A stair guard may be as low as 34 inches. Where the top of the guard also works as the handrail, it must be 34 to 38 inches. You take both from the nosing line. California did not change either one. Both match the model IRC.

The gaps in the guard. Fill the guard so a small child cannot slip through. A ball 4 inches across must not pass through any gap. That runs from the walking surface up to the height the code asks for (R321.1.3).

Two more exceptions apply here. On the open side of a stair, a gap may pass a ball 4-3/8 inches across. The triangle made by the riser, the tread and the bottom rail may pass a 6-inch ball.

On the job. Set the post height first. Cut the posts so the top rail lands at 42 inches or a touch over. Build the deck rail and the stair rail in one go. But hold the stair rail to its own rule. Check the frame with a tape before any trim goes on. These are the state floor figures. A city or county can ask for more, so ring your building department.

Which edition applies. The 2025 CRC took effect on 1 January 2026. It is Part 2.5 of Title 24. It replaced the 2022 edition. Guards moved from Section R312 to Section R321. The 42-inch height did not change. Nor did the 30-inch trigger. The 2022 edition still covers permits pulled before that date.

Plastic composite rails. An outdoor guard made of plastic composite must meet Section R507.2.2 (R321.1.4). Note the pointer has moved. The 2022 code sent you to R317.4 instead.

Sources

  • 2025 California Residential Code (Cal. Code Regs., Title 24, Part 2.5), Section R321 “Guards and window fall protection” — R321.1.2 sets the minimum guard height at 42 in (1067 mm), with the 34 in and 34–38 in exceptions on the open sides of stairs. Read it at codes.iccsafe.org.
  • 2025 CRC R321.1.1 — Where required. Sets the trigger for a guard on an open-sided floor, stair, ramp or landing: a drop of over 30 in (762 mm) to the surface below, judged anywhere within 36 in (914 mm) of the open edge. It also rules out insect screening as a guard. Same wording as the 2024 IRC. codes.iccsafe.org.
  • 2025 CRC R321.1.3 — Opening limitations. 4 in (102 mm) sphere generally; 6 in (153 mm) for the triangular opening formed by riser, tread and bottom rail; 4-3/8 in (111 mm) on the open side of stairs. This is unamended model-IRC text. The 2024 IRC R321.1.3 reads the same. codes.iccsafe.org.
  • 2025 CRC R321.1.4 — Exterior plastic composite guards. One sentence: they must comply with Section R507.2.2. The 2024 IRC R321.1.4 reads the same. The 2022 CRC (R312.1.4) pointed to R317.4 instead. codes.iccsafe.org.
  • 2024 International Residential Code, Section R321.1.2 — the model code sets a minimum guard height of 36 in (914 mm), so the California figure is 6 in (153 mm) taller. codes.iccsafe.org.
  • 2022 California Residential Code, Section R312.1.2 — superseded on 1 January 2026, but still the edition for projects permitted before that date. It carried the same 42 in height and the same 34 in open-stair-side exception; only the section number changed (R312 → R321). codes.iccsafe.org.
  • Not covered above. The window fall protection part of Section R321 was not dual-verified for this page. Check it directly at codes.iccsafe.org.

Related building rules

Frequently asked questions

How tall does a guard have to be in California?
At least 42 inches (1067 mm) on a deck, porch or landing. You measure straight up from the walking surface. The rule is CRC Section R321.1.2 in the 2025 code. The open side of a stair is not the same. It gets two exceptions that let the guard sit lower.
Why is a California guard 42 inches and not 36?
The model IRC sets 36 inches (914 mm). California changed that number in its own code. The state figure is 42 inches (1067 mm), six inches taller. The 2022 code said 42 inches too, so this is not a new rule.
When do I need a guard on a deck or porch in California?
When the drop off the open edge is more than 30 inches (762 mm). You check that drop at any point within 36 inches of the edge. It covers floors, decks, stairs, ramps and landings. Insect screen does not count as a guard.
How high are guards on the open side of a stair?
At least 34 inches (864 mm), measured up from the line that joins the stair nosings. Where the top of the guard also works as the handrail, it must be 34 to 38 inches (864 to 965 mm). Those two figures match the model IRC.
Which code edition applies in California now?
The 2025 CRC, Title 24 Part 2.5. It took effect on 1 January 2026 and replaced the 2022 edition. Guards moved from Section R312 to Section R321. The 42-inch height did not change. Ask your building department which edition covers your permit.