The state-by-state answer, updated as laws change.
11 states currently require local governments to allow ADUs by right - California, Oregon, Washington, Maine, Vermont, New Hampshire and more - while 4 states have partial or in-progress mandates, and the remaining states leave the decision to each city. No state bans ADUs outright.
| State | Statewide law? | Key statute | What it guarantees |
|---|---|---|---|
| California | Yes — statewide mandate | Gov. Code §§66310-66342 | Up to 1,200 sq ft detached; 4 ft setbacks; no parking near transit; no owner-occupancy; 60-day ministerial approval |
| Oregon | Yes — statewide mandate | HB 2001 / ORS 197.312 | ADUs required in single-family zones of larger cities; no off-street parking mandate |
| Washington | Yes — statewide mandate | HB 1337 (2023) | Cities must allow up to 2 ADUs per lot; no owner-occupancy mandate; parking can't be required within ½ mile of major transit (otherwise limited to 1-2 spaces by lot size) |
| Maine | Yes — statewide mandate | LD 2003 (2022) | At least 1 ADU allowed by-right on single-family lots statewide |
| Vermont | Yes — statewide mandate | Act 47 / 24 V.S.A. §4412 | 1 ADU allowed by-right with single-family home statewide |
| New Hampshire | Yes — statewide mandate | RSA 674:71-73 | 1 attached ADU allowed by-right in any single-family zone |
| Massachusetts | Yes — statewide mandate | Affordable Homes Act §8 (2024) | ADUs by-right in single-family zones in all 351 municipalities (effective 2025) |
| Rhode Island | Yes — statewide mandate | RIGL §45-24-37 (2024) | 1 ADU allowed by-right on owner-occupied single-family lots |
| Montana | Yes — statewide mandate | SB 528 (2023) | ADUs required by-right in larger cities' single-family zones |
| Arizona | Yes (large cities) | HB 2720 (2024) | Cities over 75,000 must allow ADUs by-right in single-family zones |
| Colorado | Yes (large cities) | HB 24-1152 | Larger cities must allow at least 1 ADU in single-family zones |
| State | Status | Key statute | Detail |
|---|---|---|---|
| Connecticut | Partial — opt-out | PA 21-29 | ADUs allowed by-right statewide unless a town formally opts out |
| Utah | Partial — internal ADUs | HB 82 (2021) | Internal ADUs allowed in most single-family zones; detached up to local rules |
| Nevada | Reform underway | AB 396 (2025) | Large cities/counties must adopt ADU ordinances by July 1, 2026 |
| Hawaii | Partial — county-led | Act 39 / county codes | ADUs ('ohana units') allowed via county ordinances; Honolulu by-right on many lots |
No statewide requirement - your city's zoning code decides. Many large cities in these states allow ADUs anyway:
| State | Status | Governed by | Detail |
|---|---|---|---|
| Texas | No statewide law — local control | Local zoning | Each city decides; Austin permissive, Fort Worth allows accessory-only ADUs under §5.301 |
| Florida | No statewide mandate — local control | Live Local Act; SB 48 failed 2026 | Local rules govern; SB 48 statewide mandate died in the House in 2026 |
| New York | Local control (NYC pilot) | Local zoning; NYC City of Yes | No statewide mandate; NYC expanded ADU eligibility via City of Yes (2024) |
| Illinois | Local control | Local zoning | Decided by city; Chicago expanded its ADU program citywide |
| Georgia | Local control | Local zoning | Decided by city; Atlanta and Savannah allow ADUs in many residential zones |
| North Carolina | Local control | Local zoning | Decided by city; Durham, Raleigh, and Charlotte permit ADUs locally |
| Minnesota | Local control | Local zoning | Decided by city; Minneapolis and St. Paul allow ADUs citywide |
| Pennsylvania | Local control | Local zoning | Decided by city; Pittsburgh permits ADUs in residential districts |
Statewide law is only the floor - size caps, setbacks, and permits are set locally. Look up your exact rules on our city-by-city ADU pages (102 cities), or check state ADU law hubs.
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