Feasibility check · 25 Bay Area cities
Can You Put an ADU on Your Lot?
Pick your city, ADU type, and target size — see what state law guarantees, what can still block you, and the researched local cost range where we have one.
What California law guarantees on most residential lots
- An ADU is allowed by right. Approval is ministerial — no public hearing, no discretionary review (Gov. Code § 66314). Cities can't require owner-occupancy for standard ADUs (AB 976, 2023).
- 800 sqft is protected. No combination of lot-coverage, floor-area-ratio, open-space, or minimum-lot-size rules may prevent an 800 sqft ADU with 4-foot side and rear setbacks (Gov. Code § 66321).
- The clock is short. The city must act on a complete ADU application within 60 days (Gov. Code § 66317).
- Impact fees are waived under 750 sqft. Larger units pay a proportional share, not full fees (Gov. Code § 66324, from AB 68).
- Conversions are the cheapest path. Converting a garage or other existing space needs no new setbacks, and no replacement parking may be required when a garage converts.
Statutes current as of July 2026 — the legislature amends ADU law almost every session, so verify before relying on any single provision.
What can still block or slow you
State law removes the zoning veto, not every constraint. Before you order a unit, check:
- Utility easements and sewer laterals under the exact spot you want to build.
- Fire access and hydrant distance — sprinklers aren't required for the ADU unless the main house has them, but access rules still apply.
- Coastal zone overlays (Pacifica and parts of the coastside) — the Coastal Act adds its own permit layer that state ADU law doesn't override.
- HOAs — CC&Rs can't ban ADUs outright (Civ. Code § 4751, from AB 670), but they can impose reasonable restrictions.
- Historic districts and hillside/geologic hazard overlays, which keep additional objective standards.
FAQ
Can my city just say no?
Not to a code-compliant ADU on a residential lot — approval is ministerial under Gov. Code § 66314. What a city can do is enforce objective standards (height, setbacks above the state floor, design rules), so feasibility questions are really about which standards apply to your lot.
Can I sell the ADU separately?
By default no — it stays part of your property. AB 1033 (2023) lets cities opt in to condo-style separate sales; ask whether yours has.
Why does the cost range vary so much?
Site work is the swing factor: utility trenching, foundation type, slope, and access can push a project well outside the published range for its city. The unit itself is the predictable part — that's the appeal of factory-built.
How accurate is the range for my lot?
Treat it as the market, not a quote. The ranges reflect what builders publish and what units in that city list for — we don't carry an error bar, because we haven't calibrated these against completed builds. The gap between the range and your real number is site work and permit fees, and only a site visit prices those.
Where do these prices come from?
Each city's range is researched from builder pricing and market listings for that city — the same data behind our Bay Area cost index. Cities where we couldn't verify ADU pricing show the law baseline only; we don't invent numbers.
City cost guides (25)
- Burlingame, CA
- Castro Valley, CA
- Cupertino, CA
- Danville, CA
- Foster City, CA
- Fremont, CA
- Half Moon Bay, CA
- Livermore, CA
- Los Altos, CA
- Los Gatos, CA
- Menlo Park, CA
- Mill Valley, CA
- Millbrae, CA
- Milpitas, CA
- Moraga, CA
- Morgan Hill, CA
- Orinda, CA
- Pacifica, CA
- Palo Alto, CA
- Pleasanton, CA
- San Anselmo, CA
- San Carlos, CA
- San Mateo, CA
- San Ramon, CA
- Saratoga, CA