ADU Rules
Accessory Structures
Rules for building accessory dwelling units (granny flats, in-law suites) including size limits, parking requirements, and owner-occupancy rules.
How ADU Rules Rules Differ by Place
Butte County, CA: Butte County ADU rules (Section 24-172)
Heavy RestrictionsButte County permits accessory dwelling units (ADUs) and junior ADUs in unincorporated areas served by municipal water and sewer, with ministerial approval, 4-foot side/rear setbacks…
Cape Coral, FL: Accessory Dwelling Unit and Guest House Rules (Cape Coral, FL)
Heavy RestrictionsCape Coral does not currently permit traditional accessory dwelling units (ADUs) with full kitchens. Under Land Development Code Section 5.2.11, only detached 'guest houses' are…
Coral Gables, FL: Coral Gables Accessory Dwelling Unit Regulations
Heavy RestrictionsCoral Gables strictly regulates accessory dwelling units through its Zoning Code and Board of Architects review. ADUs are limited to ancillary apartments in select residential zoning…
Lee County, AL: Lee County Accessory Dwelling Unit Zoning Rules
Few RestrictionsLee County's Zoning Regulations list an "Accessory dwelling unit," attached or detached from the primary house on the same lot, as its own Rural Residential use under Section 8.4(2)…
Mohave County, AZ: Mohave County Accessory Residence Rules
Few RestrictionsUnder Mohave County Ordinance 2025-06, any property that allows a single-family home may add one attached and one detached accessory residence, with an extra detached unit on lots over…
Phoenix, AZ: Two ADUs allowed per single-family lot; 5 ft setbacks
Few RestrictionsPhoenix permits up to two accessory dwelling units (one attached, one detached) on a single-family detached lot, with a third allowed on lots of one acre or more when one ADU is…
ADU Rules Rules by State
Statewide law governs this topic in many states. Each entry links to that state's full page.
Arizona
Few RestrictionsArizona's HB 2720 (2024), codified at A.R.S. 9-461.18, requires municipalities over 75,000 population to permit accessory dwelling units on single-family lots, limiting restrictive…
Arkansas
Few RestrictionsArkansas Act 313 of 2025 requires every municipality to permit at least one accessory dwelling unit by right on residential lots and prohibits cities from imposing parking…
California
Few RestrictionsGovernment Code sections 66310 through 66342, the recodified ADU law formerly at 65852.2, establish statewide ministerial approval, size minimums, and parking caps for accessory…
Colorado
Few RestrictionsColorado House Bill 24-1152 requires Tier 1 municipalities to permit at least one accessory dwelling unit on lots zoned for single-family use, preempting local bans starting June 30…
Hawaii
Some RestrictionsAct 39 (2024), codified at HRS § 46-4.8, requires every county to amend its zoning to allow at least two accessory dwelling units on residentially zoned lots with adequate water and…
Louisiana
Some RestrictionsLouisiana mandates that all accessory dwelling units comply with the Louisiana State Uniform Construction Code, preempting local building standards while leaving zoning approvals to…
Maine
Few RestrictionsPer 30-A MRS § 4364-A, enacted by LD 2003 (PL 2021 ch. 672), every Maine municipality SHALL allow at least one accessory dwelling unit as an accessory use to a single-family dwelling…
Massachusetts
Few RestrictionsThe 2024 Affordable Homes Act amended MGL Chapter 40A to require all Massachusetts municipalities to allow accessory dwelling units by-right in single-family zoning districts…
Montana
Few RestrictionsMontana SB 528, codified in 2023, requires cities and counties to allow accessory dwelling units on lots zoned for single-family use. Local governments cannot impose owner-occupancy…
New Hampshire
Few RestrictionsNew Hampshire RSA 674:71 to 674:73 requires every municipality that allows single-family homes to permit at least one accessory dwelling unit. A 2025 amendment makes one ADU allowed as…
Oregon
Few RestrictionsUnder ORS 197A.425, Oregon cities over 2,500 population and counties over 15,000 must allow at least one accessory dwelling unit on each single-family lot inside urban growth…
Rhode Island
Few RestrictionsRhode Island state law (R.I. Gen. Laws Section 45-24-73) requires municipalities to allow accessory dwelling units by right in defined circumstances on residential lots, preempting…
Utah
Few RestrictionsUtah Code 10-9a-530 requires municipalities to allow internal accessory dwelling units in owner-occupied single-family homes. Cities cannot ban internal ADUs but may regulate parking…
Vermont
Few RestrictionsVermont law requires every municipality with zoning to permit at least one accessory dwelling unit per single-family lot as a permitted use, preempting local prohibitions. The HOME Act…
Washington
Few RestrictionsWashington HB 1337 (RCW 36.70A.681) requires cities and counties to allow two ADUs per lot in urban growth areas, preempting restrictive local rules.
Cities & Counties with ADU Rules Rules
541 locations
Alabama
Arizona
California
Florida
Other Accessory Structures Topics
ADU Impact Fees
Impact fees, school fees, utility hookup charges, and waivers for ADUs. Many jurisdictions exempt ADUs under 750 sq ft from impact fees per state law.
ADU Owner Occupancy
Whether the property owner must live on-site to operate an ADU, deed-restriction requirements, and recent state-law changes lifting owner-occupancy rules.
ADU Rental Restrictions
Whether an ADU can be rented short-term (Airbnb), 30-day minimums, separate rental licenses, and long-term lease requirements.
Shed & Carport Rules
When a storage shed or carport needs a permit, the square-footage exemption thresholds, and the setback and height limits that apply either way.
Garage Conversions
Rules for converting a garage into living space, including whether you need to replace the lost parking and what building codes apply.
Tiny Homes
Zoning rules for tiny houses on wheels and foundations, including minimum square footage requirements and where they can be placed.