ADU Regulations Lookup by State and City

Find the ADU (Accessory Dwelling Unit) rules that apply to your property. Select your state and city below to see local regulations on granny flats, in-law suites, backyard cottages, and other ADUs -- including size limits, parking, setbacks, owner-occupancy requirements, and permitting timelines.

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ADU-Friendliness by State - All 50 States + DC

The grid below shows ADU-friendliness scores for every US state and DC. Currently, 21 states have statewide ADU laws, 13 states are rated "Easy" for ADU construction, and 9 are rated "Difficult" or worse. Click any state for full ADU regulations, city-level data, and building guides.

WA 96 Easy Washington VT 95 Easy Vermont AZ 93 Easy Arizona CA 93 Easy California OR 93 Easy Oregon CO 91 Easy Colorado MN 88 Easy Minnesota MA 85 Easy Massachusetts CT 83 Easy Connecticut ME 80 Easy Maine FL 78 Easy Florida MT 78 Easy Montana NV 78 Moderate Nevada NY 76 Easy New York HI 75 Moderate Hawaii VA 75 Moderate Virginia DC 70 Moderate District of Columbia NJ 66 Moderate New Jersey RI 63 Moderate Rhode Island NH 55 Moderate New Hampshire NM 55 Moderate New Mexico UT 50 Moderate Utah AK 45 Moderate Alaska AL 30 Difficult Alabama AR 30 Difficult Arkansas DE 30 Moderate Delaware GA 30 Moderate Georgia ID 30 Moderate Idaho IL 30 Moderate Illinois IN 30 Difficult Indiana IA 30 Difficult Iowa KS 30 Difficult Kansas KY 30 Difficult Kentucky LA 30 Moderate Louisiana MD 30 Moderate Maryland MI 30 Moderate Michigan MS 30 Very Difficult Mississippi MO 30 Moderate Missouri NE 30 Moderate Nebraska NC 30 Moderate North Carolina ND 30 Moderate North Dakota OH 30 Moderate Ohio OK 30 Moderate Oklahoma PA 30 Moderate Pennsylvania SC 30 Difficult South Carolina SD 30 Moderate South Dakota TN 30 Moderate Tennessee TX 30 Moderate Texas WV 30 Difficult West Virginia WI 30 Moderate Wisconsin WY 30 Moderate Wyoming

What States Allow ADUs?

As of 2026, ADUs are technically allowed in all 50 states, but the ease of building one varies enormously. States with statewide ADU laws (like California, Oregon, Washington, and Vermont) make it easy by preempting local zoning restrictions. In states without statewide laws, you may face anything from streamlined permitting to outright de facto bans depending on your city.

Category	Count	Examples
Statewide ADU Law	21	CA, OR, WA, CT, VT, MN, FL, CO, NY, MA
Easy to Build	13	Most states with statewide laws
Moderate	29	TX, GA, NC, OH, MD, NV, DC
Difficult	8	AL, AR, IN, SC, WV
Very Difficult	1	MS

What Is an ADU (Accessory Dwelling Unit)?

An ADU -- also known as a granny flat, in-law suite, backyard cottage, casita, or carriage house -- is a secondary housing unit on a single-family residential lot. ADUs are self-contained, with their own entrance, kitchen, bathroom, and living space. They can be detached (a standalone structure in the backyard), attached (an addition to the main house), or a conversion of existing space (a garage, basement, or attic).

ADUs have surged in popularity as a solution to the US housing shortage. They allow homeowners to add rental income, house family members, or age in place while increasing housing supply without changing neighborhood character. A wave of state legislation since 2019 has dramatically expanded the right to build ADUs across the country.

How Much Does an ADU Cost to Build?

ADU construction costs vary widely by location, size, and type. On average in 2026, a detached ADU costs between $150,000 and $350,000 to build. Garage conversions and attached ADUs typically cost $100,000 to $200,000. Pre-fabricated (prefab) ADUs can range from $80,000 to $250,000 including installation. Costs are highest in California and the Northeast, and lowest in the South and Midwest. Key factors include foundation type, utility connections, local labor rates, and permitting fees.

Key ADU Regulations to Check

Before building an ADU, you need to understand several key regulations that vary by state and city:

Size limits: Maximum square footage, often 800-1,200 sq ft or a percentage of the primary home
Owner occupancy: Whether the owner must live on the property (in the main home or ADU)
Parking: Whether additional off-street parking spaces are required for the ADU
Setbacks: Minimum distance from property lines, typically 3-5 feet for rear/side
Height limits: Maximum ADU height, usually 16-25 feet
Permitting: Whether ADUs need special use permits or are allowed by right
Impact fees: Development charges that can add $5,000-$30,000+ to project costs
Rental restrictions: Whether the ADU can be rented, and if short-term rentals are allowed

Frequently Asked Questions

Which states have the best ADU laws?

As of 2026, the most ADU-friendly states are California, Oregon, Washington, Vermont, Maine, Connecticut, Minnesota, and Montana. These states have statewide laws that preempt local zoning restrictions, prohibit owner-occupancy requirements, eliminate parking mandates, and streamline permitting. California and Oregon have the longest track records, while states like Florida, New York, Colorado, and Massachusetts passed major ADU reforms in 2023-2024.

Can I build an ADU in my backyard?

In most US states, yes -- but the specific rules depend on your state and local jurisdiction. In states with statewide ADU laws (like CA, OR, WA, CT, VT), you have a legal right to build an ADU on most single-family lots. In states without statewide laws, check your city's zoning code. You will need to comply with setback requirements, size limits, and building codes regardless of location.

Do I need to live on the property to have an ADU?

It depends on your state and city. Many of the newer statewide ADU laws (California, Oregon, Washington, Connecticut, Vermont, Maine, Montana, Minnesota) prohibit owner-occupancy requirements, meaning you can rent both the main home and the ADU. However, some states and cities still require the property owner to live on-site, either in the main home or the ADU. Check your specific location using our lookup tool.

How long does it take to get an ADU permit?

Permitting timelines vary significantly. States with streamlined ADU laws have maximum review periods: California requires cities to act within 60 days, Vermont within 30 days. In states without mandated timelines, permitting can take 3-12 months depending on local bureaucracy, plan review backlogs, and whether discretionary approval is required. Some cities offer pre-approved ADU plans that can cut permitting time to under 2 weeks.

Can I rent out my ADU on Airbnb?

Short-term rental rules for ADUs vary by state and city. Some states with statewide ADU laws (like California) explicitly prohibit short-term rentals of ADUs. Others (like Arizona and Washington) allow it. Even in states that permit ADU short-term rentals, your city may have separate short-term rental ordinances that apply. Always check both ADU regulations and short-term rental rules for your jurisdiction.

What is the difference between an ADU and a tiny home?

An ADU is a permanent, code-compliant secondary dwelling on an existing residential lot. A tiny home is a small dwelling (typically under 400 sq ft) that may be on wheels or on a foundation. ADUs are regulated under standard building and zoning codes, while tiny homes on wheels are often classified as RVs and face different (usually more restrictive) zoning rules. A tiny home on a permanent foundation on your property would effectively be an ADU and subject to ADU regulations.