Railing Installation on the Peninsula

One request goes to one contractor who works your area. He replies by phone with what he saw in the photos and what he would need to confirm on site. No bids from a list of companies.

Under the 2025 California Residential Code, which applies to one- and two-family homes and townhouses:

• A guard is required along any open-sided walking surface — deck, porch, balcony, landing or stair — that is more than 30 inches above the floor or grade below, measured at any point within 36 inches of the edge (CRC § R321.1.1).
• The guard must be at least 42 inches high. On the open side of a stair, at least 34 inches (§ R321.1.2).
• Openings may not pass a 4-inch sphere. On the stair side the limit is 4⅜ inches, and the triangle between tread, riser and bottom rail may not pass a 6-inch sphere (§ R321.1.3).
• A stair with four or more risers needs a handrail on at least one side (§ R318.7.8), 34–38 inches above the tread nosings (§ R320.2), continuous for the flight (§ R320.5).

Below the 30-inch threshold no guard is required by this section; if you plan to add one anyway, confirm the design with the city.

• A deck or porch built without one that is over 30 inches at some point. A deck that sits low on one side and over a slope on the other is measured at the slope.
• A stair with four or more risers and no handrail.
• An old railing that cannot be brought to the current rules without replacing the posts or most of the run. Where the existing guard can be made compliant — a taller top assembly, new infill — that is repair; see railing repair.

• Post attachment. The connection between the posts and the deck frame carries the whole guard. Posts notched over the rim joist or lagged to a single board are the usual failure point, so the rim and joists get looked at before the railing is priced.
• Height from the walking surface. 42 inches is measured from the deck boards; a deck that will be re-boarded changes the number.
• Infill. Vertical pickets, horizontal cable, glass and composite panels all have to meet the 4-inch sphere rule; cable systems meet it when tensioned and spaced correctly.
• Stair geometry. Stair-side guard and handrail heights are measured from a line along the tread nosings, so the whole flight needs to be in the photos.

Whether a new or replacement railing needs a building permit is decided by the city. Palo Alto, Menlo Park and Mountain View each publish their own exempt-work list; railings are not on any of them, so the answer comes from the Building Division, not the list. City details: Mountain View, Palo Alto, Menlo Park. For the deck itself, see when a fence or deck needs a permit.

• Measure from the deck surface to the ground at the lowest point within 3 feet of the edge.
• Photograph the edge from below so the rim joist shows.
• For a stair, photograph the whole flight from the bottom.
• Say whether the railing meets the house wall at either end.

No. The guard requirement starts above 30 inches (CRC § R321.1.1).

Not as a required guard on a deck, porch or balcony — the California Residential Code sets 42 inches. 34 inches applies only on the open side of a stair.

The code limits openings, not the direction of the infill. A cable system meets it when tensioned and spaced so a 4-inch sphere cannot pass.

Ask the city's Building Division, or let the contractor ask. None of the three cities list railings as exempt work.