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 25 verified city ordinances and the state ADU floor.

By Jarrod·Editor·Last verified May 2026

Property address

Auto-completes as you type. CA addresses only. Lot size (sqft) From your property tax bill, county assessor, or Zillow's "Public facts" tab. Most CA suburban lots are 4,000–10,000 sqft.

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

We'll match your address to one of 25 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).

Methodology. Address geocoding via Mapbox. City rules from each municipality's official ADU page (scraped + manually verified Apr 2026; refreshed quarterly). State floor from CA Government Code §65852.2. Cost figures from 8 published 2026 builder cost guides (median of medians; see methodology). Buildable area assumes a square lot and the city's standard front-yard setback (15 ft default). 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 (CA Gov Code §65852.2): every CA city must allow at least 800 sqft, 16 ft height, 4 ft side & rear setbacks, and waive parking within ½ mile of transit.
City overlay for 25 verified jurisdictions: max ADU size, height limits, parking rules, JADU limits, and notable local provisions (historic districts, coastal zones, etc.).
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. We assume a square lot. If your lot is long & narrow (or pie-shaped), the buildable footprint can swing 20-40%.
Easements, sewer laterals, tree-protection zones. Always pulled at architect / surveyor stage.
Your fee schedule. Permit + impact fees vary $5k–$25k by city. Currently shown as a generic range; we're collecting per-city schedules for v2.

v2 of this tool (in development) adds parcel-level lookup from county GIS feeds — actual lot dimensions, zoning district, and buildable area math from real polygons. Updates: subscribe via the about page.