California: homes, climate zones and who licenses the work

Age changes what applies to a house. In general, anyone paid to do work that disturbs painted surfaces in a home built before 1978 must be certified in lead-safe work practices under the EPA's Renovation, Repair and Painting Rule, which the EPA administers directly in California.

The 2021 International Energy Conservation Code assigns every county a climate zone from 1 to 8 and a moisture regime: A for moist, B for dry, C for marine. Zones 7 and 8 have no letter. Here is how California's residents divide among them, by the county they live in.

ENERGY STAR rates windows, doors and skylights for four climate zones of its own. California spans 4: South-Central (96.5% of residents), North-Central (2.1% of residents), Northern (0.9% of residents), Southern (0.5% of residents).

By NOAA's 1991–2020 climate normals, counties here average 17 days a year with a low of 32°F or colder, weighted by where people live. The range runs from 1 day in the mildest county to 196 in the coldest.

1.3% of residential structures in California carry a National Flood Insurance Program policy: 140,683 policies, in FEMA's count as of August 3, 2026.

In FEMA's National Risk Index, 33 of 58 counties rate high or very high for riverine flooding; 8 of 58 counties rate high or very high for coastal flooding.

3 of California's 58 counties are inside the federal imported fire ant quarantine, home to 39.4% of its residents. The federal quarantine requires a certificate to move soil, sod, nursery plants with soil attached, used soil-moving equipment, and hay or straw stored on the ground out of the quarantined area.

Before anyone starts work, check the license with the agency below. Where the state does not license a trade, cities and counties may; ask the one where the house is.