Easiest Cities to Build an ADU (2026)

Top 25: Easiest to Build

Based on each city's ADU zoning and permitting requirements. "Permissive" cities allow ADUs by right in most residential zones with clear size limits and straightforward permits. "Strict" cities require conditional use permits, public hearings, or impose restrictions that make ADUs impractical for most properties.

1. 1

   Dallas County, TXFew RestrictionsNot 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, TXFew RestrictionsRequired 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, CAFew Restrictions

   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, MDFew Restrictions50% 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, WAFew RestrictionsBanned (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, TXFew RestrictionsOver 200 sq ft

   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, CAFew Restrictions1,200 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, CAFew Restrictions

   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, AKFew Restrictions900 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, CAFew RestrictionsNot 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.

11. 11

    Fullerton, CAFew RestrictionsUp to 1,200 sq ft (2-bedroom detached)

    Fullerton permits ADUs and Junior ADUs (JADUs) in compliance with California Government Code Sections 65852.2 and 65852.22. One ADU and one JADU are allowed on any single-family lot. ADUs up to 800 square feet with a 4-foot rear and side setback are approved ministerially without discretionary review. No owner-occupancy requirement applies to ADUs (JADUs require owner occupancy). No parking is required if within half a mile of transit.

12. 12

    Mountain View, CAFew RestrictionsAt least 1,200 sq ft

    Mountain View ADU regulations follow California Government Code 65852.2 as amended by AB 68, AB 881, SB 13, and AB 1033. Ministerial approval applies to most ADUs and JADUs on single-family lots.

13. 13

    Concord, CAFew Restrictions

    Concord must allow at least one ADU plus one Junior ADU per single-family residential lot under California Government Code §65852.2 (AB 68/881). ADUs up to 800 sq ft cannot be denied. Permits process within 60 days, 4-foot setbacks, no parking near transit, no impact fees under 750 sq ft.

14. 14

    Alameda County, CAFew Restrictions

    Alameda County complies with California Government Code 65852.2 mandating ministerial ADU approval. ADUs up to 1,200 sqft for detached and JADUs up to 500 sqft are allowed on most residential lots.

15. 15

    Walnut Creek, CAFew Restrictions

    Walnut Creek must allow Accessory Dwelling Units (ADUs) and Junior ADUs on all residential lots under California Government Code Section 65852.2, as strengthened by AB 68, AB 881, and SB 13. Permitted detached ADUs up to 800 sq ft require 4-foot side/rear setbacks, no replacement parking within half-mile of transit, and 60-day permit processing.

16. 16

    Durham, NCFew Restrictions1,000 sq ft single story or 1,200 sq ft total

    Durham allows one ADU per lot under UDO Sec. 5.4.2. Max 1,200 sq ft heated area. No special use permit or additional parking required. Attached, detached, or internal.

17. 17

    Livermore, CAFew Restrictions60 days

    Livermore must allow ADUs under CA Gov Code §65852.2. Detached ADUs up to 800 sq ft with 4-ft setbacks, JADUs up to 500 sq ft, 60-day permit review.

18. 18

    Galt, CAFew RestrictionsUp to 800 sf ministerial

    Galt must allow Accessory Dwelling Units on residential lots under California Government Code 65852.2. Detached ADUs up to 800 square feet are ministerial, with 4-foot side and rear setbacks and no required replacement parking near transit.

19. 19

    Bakersfield, CAFew Restrictions

    Bakersfield processes ADU and junior ADU applications ministerially under California Government Code 65852.2 and SB 1211, which preempt local restrictions on parking, setbacks, and density. Detached ADUs up to 1,200 sq ft and attached ADUs up to 50 percent of the main home (minimum 800 sq ft) are allowed on any residential lot. Statewide exemption standards require 4-foot side and rear setbacks and no owner-occupancy requirement through 2025. Permit review is 60 days or the application is deemed approved. A JADU up to 500 sq ft carved from the primary home is also allowed. HOAs cannot unreasonably restrict ADUs under Civil Code 4751.

20. 20

    Boise, IDFew Restrictions900 sq ft or 10% lot

    Boise allows one ADU (attached or detached) on every single-family lot. Idaho Code Section 67-6511A (2023) limits cities from banning ADUs in single-family zones. Boise permits ADUs up to 900 sq ft with streamlined review.

21. 21

    Somerville, MAFew Restrictions900 sq ft by right

    Somerville was an early Massachusetts adopter of ADU zoning and now complies with the 2024 Affordable Homes Act mandating ADUs by right in all single-family zones statewide.

22. 22

    Raleigh, NCFew Restrictions

    Raleigh allows accessory dwelling units (ADUs) by-right in all residential zoning districts under UDO Section 2.5.1, making it one of the most permissive ADU regimes in North Carolina. Detached and attached ADUs up to 1,000 square feet or 50 percent of the primary dwelling (whichever is less) are permitted without a special use permit. Short-term rental of ADUs is prohibited; they must serve long-term occupancy only.

23. 23

    Sutter County, CAFew Restrictions1,200 sq ft

    In unincorporated Sutter County, ADUs are ministerially permitted by Zoning Clearance in all districts allowing single-family or multifamily dwellings. Detached ADUs may reach 1,200 sq ft. Setbacks are 4 ft side and rear, height at least 16 ft, no parking required, and impact fees are waived under 750 sq ft.

24. 24

    Oakland, CAFew Restrictions

    Oakland permits ADUs on all residential lots under Gov Code §65852.2 and Planning Code 17.103. Ministerial 60-day approval up to 1,200 sq ft, 4-foot setbacks, and no parking mandate within half a mile of transit.

25. 25

    Austin, TXFew Restrictions

    Austin's HOME Initiative (Ord. 20231207-001, effective Feb 5, 2024) allows up to 3 housing units, including ADUs and tiny homes, on lots zoned SF-1, SF-2, and SF-3.

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