Can I build an ADU on my lot?

Type your California address and lot size. We'll check city rules, estimate the maximum ADU size your lot can fit, and show typical 2026 cost ranges — sourced from 28 verified city ordinances and the state ADU floor. Results also show your city or county's ADU permit count for 2025, its median build time where the state's records support one, and what changes under state law in 2027.

By Jarrod·Editor·Last verified October 2026

Enter your address and lot size to see what you can build.

We'll match your address to one of 28 verified California city ordinances and calculate buildable area from setback rules. If we don't have detailed data for your city, we fall back to the state ADU floor (which still gives you most of the relevant rules). Either way you get your city or county's permit count and measured build time where the state's records support them.

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Tell us a little about the project and we will introduce you by email to one builder, or one builder-matching service, that serves your area. A matching service shares your details with the contractors it matches you with; a builder keeps them. If none in our network covers it yet, we will say so and point you to the licensed builders listed for your city; if that changes later, we will ask you again before sharing your details. Builders may pay us a referral fee for an introduction; that never changes the cost ranges, rules or build-time figures published on this site, and no builder can pay to appear in our directory.

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Methodology. Address geocoding via Mapbox: the address you type goes from your browser to Mapbox to find the city. It is never added to a page address and is not sent to us as a form field or analytics value; our analytics record only that the form was submitted (see privacy). City rules from each municipality's official ADU page (collected and manually checked April 2026). State floor from California Government Code sections 66314 to 66323. Build times and permit counts are city-level figures from the state housing department's Annual Progress Report data (see build times and data). A mailing address often names a place that is not the city issuing the permit, so where the name is not a city we hold figures for, we check which city limits its ZIP Code area falls inside, using the Census Bureau's 2020 ZIP Code Tabulation Area and place boundary files. Those are shares of land area, a ZIP Code area only approximates a postal ZIP Code, and where an area is split we show each jurisdiction instead of picking one. Cost figures from 8 published 2026 builder cost guides (median of medians; see methodology). Buildable area assumes a square lot and a 15 ft front-yard setback, and does not subtract your existing house. Real lots are rarely square — this is directional, not a substitute for an architect or city counter visit.

How this works (and what it can't tell you)

What we check

State ADU floor (California Government Code sections 66314 to 66323): a city's size, lot-coverage, floor-area-ratio, open-space, front-setback and minimum-lot-size rules may not prevent an ADU of at least 800 sqft with 4 ft side & rear setbacks; a detached ADU may be at least 16 ft tall, with higher state minimums in the transit and multifamily cases listed in section 66321; and no parking may be required within ½ mile walking distance of public transit or in the other cases listed in section 66322.
City overlay for 28 verified jurisdictions: max ADU size, height limits, parking rules, JADU limits, and notable local provisions (historic districts, coastal zones, etc.).
Local track record: the median time from building permit to completion in your city or county, where enough completed projects are on the state's records, and the ADU permits it reported for 2025 and 2024.
2027 law changes: two detached ADUs on a single-family lot (AB 956), and impact fees for up to two ADUs (SB 1117): fees do not include utility connection fees or capacity charges, and for ADUs over 750 sqft are calculated only on the area above 750 sqft.
Buildable footprint from your lot size minus setbacks — the upper limit on a single-storey ADU's footprint regardless of what the city's max-size cap says.
Cost range from our calibrated 2026 regression (8 published builder pricing sources) adjusted for your city's cost region.

What we can't tell you (yet)

Your specific zoning district. Most CA single-family parcels qualify, but multi-family, hillside, historic, and coastal overlays add layers we can't see from an address alone.
Your actual lot dimensions, or where your house sits. We assume a square lot and do not subtract the existing house, garage or driveway. If your lot is long & narrow (or pie-shaped), the buildable footprint can swing 20-40%.
Which side of a city limit you are on. Many ZIP Code areas cover both a city and unincorporated county land, and some mailing names (Van Nuys, La Jolla) belong to a larger city. We say which jurisdictions your ZIP Code area covers; your property tax bill or the county assessor's parcel viewer says which one your property is in.
Easements, sewer laterals, tree-protection zones. Always pulled at architect / surveyor stage.
Your fee schedule. Permit + impact fees vary $5k–$25k by city. Ask the city for its current schedule.

This tool does not look up parcel records. For your exact lot lines, zoning district and overlays, use your county assessor's parcel viewer or ask the city planning counter.