State Law vs. Local City Rules: Who Wins?

Every ADU question you'll ever ask has the same two-layer answer, so let's make the layers explicit.

Layer 1 — State law: the floor. Everything this module covered: ministerial approval, 4-foot setbacks, the 800 SF guarantee, height tiers, parking caps, the owner-occupancy ban, HOA limits, review deadlines. Cities cannot go below the floor. Period.

Layer 2 — Local ordinance: the details above the floor. Cities legitimately decide things state law leaves open: exact maximum size (1,200 SF? more?), detached height above 16/18 feet, front setback dimensions, objective design standards (materials, roof pitch), fees above the state minimums, and which extras (like two-story detached units) they'll allow. This is why the same ADU design can be approvable in one city and need changes in the neighboring one.

When the layers conflict: state wins. If a local rule contradicts a state protection, the local rule is invalid — and HCD, the state's housing department, actively reviews city ordinances. Cities with non-compliant ordinances can lose them entirely, leaving state standards to apply directly. Some cities also just… haven't updated their websites. If a city counter tells you something that contradicts this module, the polite response is to ask them to show you the requirement in their current, HCD-compliant ordinance. (Module 10 covers what to do when the city is wrong.)

Your practical workflow: learn the state floor (done — this module), then pull your city's current ADU ordinance or handout for the details. Any professional feasibility review does both.