Decks on the fog coast: wood, railings and permits

The climate and wood

The USDA Forest Products Laboratory rates how hard a place's climate is on wood left outdoors above the ground with a decay hazard index: the higher the number, the greater the hazard.

Its table of values for 1971 to 2000 lists Eureka at 44.5.

Its map groups places into three bands: under 35, 35 to 65, and over 65.

The index compares places; it does not predict how fast decay spreads or when a particular structure will fail.

Source: USDA Forest Products Laboratory: Decay Hazard (Scheffer) Index Values, 1971-2000 (FPL-GTR-179)

Railings

Guards are required on open-sided floors, stairs, ramps and landings that are more than 30 inches above the floor or grade below at any point within 36 inches of the open edge (R321.1.1).

Insect screening does not count as a guard.

Required guards have to be at least 42 inches high (R321.1.2).

On the open sides of stairs, guards have to be at least 34 inches high, measured from a line along the nosings.

Where the top of a guard on the open side of stairs also serves as the handrail, it has to be at least 34 and no more than 38 inches high, measured from a line along the nosings.

Required guards cannot have openings that a 4-inch sphere can pass through.

Guards on the open side of stairs cannot have openings that a 4-3/8-inch sphere can pass through.

The triangle at the open side of a stair, formed by the riser, the tread and the guard's bottom rail, cannot let a 6-inch sphere pass through.

Source: 2025 California Residential Code, Chapter 3 (UpCodes)

Stairs

The rules for stair risers and treads, and their exceptions, are in section R318.7 of the 2025 California Residential Code.

Source: 2025 California Residential Code, Chapter 3 (UpCodes)

Permits

The county says the work that does not need a building permit is described in Humboldt County Code §331-11(a)(4) and California Building Code §105.2.

Source: Humboldt County: First Time Applying for a Building Permit

Attached decks and the ember-resistant zone

The ember-resistant zone within 5 feet of a building, counting any attached deck as part of the building, is set out in Public Resources Code §4291, and its details are left to the Board of Forestry and Fire Protection's regulations.

Under that section, the requirement for the zone (“Zone 0”) does not take effect for new buildings until the Board updates its regulations and its guidance document, and it takes effect for existing buildings three years after that.

Sources: California Public Resources Code §4291; Board of Forestry and Fire Protection: Defensible Space Zones