Free ADU check
Your state may already have answered. Eight states set a floor of more than one home on most single-family lots. Pick yours.
Utah and Arkansas: cities and towns only. Massachusetts: not Boston. Vermont: a duplex.
California
at least 3 homes
The house + an ADU + a junior ADU, by state law
Lot with a single-family home in a residential or mixed-use zone; approval is ministerial. The statute allows up to 4 in some combinations; 3 is the cautious reading.
Cal. Gov. Code § 66323Also may applySB 9 (§ 65852.21 / § 66411.7) allows 2 units, or a lot split into 2×2, in urbanized areas; owner-occupancy and charter-city litigation apply.
Statute read on the state’s own site, Oct 8, 2026
State lawThe floor no city can go under, with its statute.
City zoningWhether the district allows an ADU, where we’ve read the code.
The lotIts size, its shape, and whether it sits in a flood zone.
Go deeper
Every state law the check applies to a lot, what the check reads, and the questions people ask before they design.
Eight states set a floor of 2+ homes on most single-family lots (Vermont’s is a duplex, not an ADU); a law may apply in seven more, depending on the lot. Each statute was read on the state’s own site on Oct 8, 2026.
A state that is not listed has no law here we apply to a lot: either the research found none that sets a per-lot floor, or it has not covered the state yet. Your city’s zoning decides.
At least 3 homes
the house + an ADU + a junior ADU
At least 2 homes
the house + 1 ADU
At least 2 homes
a duplex
At least 2 homes
the house + 1 ADU
At least 2 homes
the house + 1 ADU
At least 2 homes
the house + 1 internal ADU
At least 2 homes
the house + 1 ADU
At least 2 homes
the house + 1 ADU
May apply
depending on the lot
May apply
depending on the lot
May apply
depending on the lot
May apply
depending on the lot
May apply
depending on the lot
May apply
depending on the lot
May apply
depending on the lot
Colorado is read from the signed act. California: The statute allows up to 4 in some combinations; 3 is the cautious reading.
SourceEach statute, read on the state legislature’s own site, Oct 8, 2026
The buildable envelope exists only where a district’s rules have been read; elsewhere the row reads “code not yet read”.
SourceCounty parcel records · FEMA flood maps · state statutes
Check the state rules and local zoning that apply to your address, then review the existing buildings, lot conditions, overlays and utility requirements. Buildability provides a preliminary address-based check with available sources; unresolved conditions still need confirmation before design or construction.
The applicable state law and local code determine size limits, with project type and lot conditions affecting the result. Check floor area, height, lot coverage and setbacks together before paying for a design that may need revision. The full report gives the ADU size and height limits for your lot where we have read the code.
Setbacks depend on the governing rules and whether the project is detached, attached or a conversion. Verify the current code, property boundaries, easements and any project-specific exceptions; a map outline does not replace a boundary survey.
Confirm the allowed ADU type, size, setbacks, height, access, utilities and approval path, and list any unanswered questions. Bring that record to planning staff and your designer so design work starts with the known constraints.
An accessory dwelling unit: a second, smaller home on a single-family lot, also called a granny flat, in-law suite or backyard cottage. It can be detached (a backyard cottage, built new), attached (an addition that shares a wall with the house), converted from existing space like a garage or basement, or built inside the house as a junior ADU (JADU).
Read from each statute on Oct 8, 2026: California (Cal. Gov. Code § 66323), Massachusetts (M.G.L. c. 40A, § 3), Maine (30-A M.R.S. § 4364-B), New Hampshire (RSA 674:72–73), Utah (Utah Code § 10-21-303, inside the house, in cities and towns), Arkansas (Ark. Code Ann. § 14-56-205, in cities and towns) and Iowa (Iowa Code § 364.3(23); § 331.301(29)). A law may also apply in Oregon, Washington, Colorado, Montana, Arizona, Connecticut and Rhode Island, depending on the city’s size, the lot, or whether the town opted out.
California guarantees at least 3 homes (the house + an ADU + a junior ADU) on a lot with a single-family home (Cal. Gov. Code § 66323). Depending on the lot, more may apply: SB 9 (§ 65852.21 / § 66411.7) allows 2 units, or a lot split into 2×2, in urbanized areas; owner-occupancy and charter-city litigation apply. The free Score names the floor on your lot and what may apply beyond it.
A state ADU law binds the city’s zoning; whether it also overrides your HOA’s covenants (CC&Rs) depends on the state. Read your CC&Rs before you design.
It depends on the state law and your city’s code. Where a state floor applies, the free Score prints its conditions for your lot, owner-occupancy included: Utah’s ADU, for one, must be inside an owner-occupied single-family home.
Yes. We read your lot size from county parcel records and the flood zone from FEMA, and apply the state law that covers your address. The answer is for your lot, not a generic one.
Nine factors (zoning, flood, seismic, soil, radon, wildfire, utilities, terrain, and lot geometry) for any U.S. address, in 20 seconds.
Free to score · Property Report $99 · No record, no charge
Buildability