Spring ADU Rules by City & State (2026)

Fewest Restrictions

1. 1
   Dallas County, TXNot required (residential)

   No county ADU restrictions. Texas counties lack zoning authority, so accessory dwelling units can be built without county zoning approval. No county building permit for residential structures. Septic capacity (TCEQ) and floodplain rules may apply.

2. 2
   Tarrant County, TXRequired for construction

   Tarrant County has no ADU ordinance because Texas counties lack zoning authority. Texas has no statewide ADU mandate. ADUs are effectively unregulated, subject only to HOA rules and floodplain limits.

3. 3
   Brentwood, CA

   Brentwood must allow Accessory Dwelling Units on any single-family lot under California Government Code Section 65852.2, as expanded by AB 68, AB 881, and SB 13. Detached ADUs up to 800 sq ft with 4-foot setbacks are ministerial approvals processed within 60 days. AB 1033 now allows selling an ADU separately from the primary home.

4. 4
   Montgomery County, MD50% of principal or 1,200 sq ft

   ZTA 19-01 (Oct 2019) allows ADUs by right in most residential zones. Max 1,200 sq ft or 50% of principal dwelling. No extra parking needed. Owner occupancy required.

5. 5
   Kennewick, WABanned (RCW 36.70A.683)

   Kennewick (Benton County, population approximately 84,000) is a Washington city subject to the state's 2023 ADU preemption statute, House Bill 1337 codified at RCW 36.70A.680 through RCW 36.70A.700. Because Kennewick exceeds the 25,000-population threshold and lies within a fully-planning GMA county (Benton County), it must permit two accessory dwelling units (ADUs) per lot in all areas zoned predominantly for residential use. Local detail is implemented through Title 18 of the Kennewick Municipal Code (Zoning), hosted on Code Publishing at https://www.codepublishing.com/WA/Kennewick/.

6. 6
   Collin County, TXNot required

   Collin County has no zoning authority over ADUs in unincorporated areas. Property owners may build accessory dwelling units, guest houses, or casitas without county zoning approval, subject only to IRC building permits, septic permits (On-Site Sewage Facility rules), and any deed restrictions/HOA rules.

7. 7
   Santa Clara County, CA1,200 sq ft

   In unincorporated Santa Clara County, ADUs are regulated under Zoning Ordinance Section 4.10.015 consistent with California ADU law. One ADU plus one Junior ADU is allowed per legal lot with a single-family residence, reviewed ministerially with no discretionary hearing.

8. 8
   Temecula, CA

   Temecula must allow ADUs and JADUs on single-family and multi-family lots under California Government Code §65852.2 and §65852.22. Recent state laws (SB 1211, AB 2533, AB 1033) expand allowed counts, ease parking, and permit separate sales. ADU permits are ministerial with 60-day review.

9. 9
   Anchorage, AK900 sq ft or 40 percent

   Anchorage passed major ADU reform 2021-2023 under AMC Title 21. ADUs are now allowed by right on most single-family lots, up to 900 square feet or 40 percent of the main home, with one off-street parking space.

10. 10
    Napa, CANot required (AB 587)

    City of Napa permits ADUs and JADUs on residential lots under Napa Municipal Code Title 17, consistent with California Gov Code §65852.2 (renumbered §66310-66339 by SB 477) and §65852.22. Detached ADUs up to 1,200 sq ft; JADUs to 500 sq ft.