Where You Can (and Can’t) Build an ADU in Connecticut

Accessory Dwelling Units (ADUs) have rapidly shifted from niche, luxury projects to a key part of Connecticut’s attempts at housing reform.

In 2021, Connecticut passed Public Act 21-29, a statewide zoning reform that required every municipality to allow ADUs by default. But the real story is what happened after: dozens of towns opted out, customized the rules, or introduced limitations.

This guide exists to cut through the confusion that caused. Our goal is a town-by-town, law-by-law breakdown of where you can and can't build and ADU, what you can build, and under what conditions.

Looking for more ADU Guides, or something specific? Check out our other blogs:

• Building an ADU in Connecticut: A Straight-Talk Guide for Homeowners

• ADU Design Styles + Visual Inspiration

• Where You Can (and Can’t) Build an ADU in Connecticut

The Statewide Baseline: Connecticut Public Act 21-29

Effective January 1, 2022, this law:

• Legalized ADUs by default in all residential zones (unless a town opts out)

• Allowed attached or detached ADUs up to 1,000 sq ft

• Eliminated the requirement for additional parking spaces

• Required that ADUs comply with building and health codes

  
  

🧐 What is Public Act 21-29 and how does it affect my property? This law forms the foundation for ADU construction across Connecticut—unless your town has opted out or created its own rules.

However, municipalities were given the right to opt out of the default language if both their local Planning & Zoning Commission and their Board of Selectmen (or equivalent) voted to do so before January 1, 2023. You can read the regulations on The State of Connecticut's website here.

Connecticut Towns That Have Opted Out (Or Modified the Law)

❓ Does my town allow ADUs under the new state law? This section helps clarify where your local zoning stands today.

A growing number of municipalities have chosen to opt out or customize the law to fit their local zoning codes.

Examples of Opt-Outs (as of 2024):

• Guilford: Opted out to "preserve historical character"

• Madison: Opted out but began drafting more limited local rules

• Southbury: Opted out citing septic and density concerns

• Orange: Opted out, reaffirming local zoning control (Source)

Examples of Modified Adoption:

• West Hartford: Allows ADUs with design and lot size restrictions (Source)

• New Haven: Supports ADUs with reduced parking and higher density (Source)

• Hamden: Allows detached ADUs only in select zones, subject to design review

⚠️ Always verify with your local planning department. Many towns have adopted custom ADU rules that differ widely from the state baseline.

The Parking Debate: One Spot or None?

🚗 Do ADUs require additional parking in Connecticut? It depends on your town—even though the state says no.

While Public Act 21-29 prohibits requiring extra parking spaces for ADUs, some towns have reintroduced parking minimums in their local ordinances. For example:

• Westport, CT: Requires one additional off-street parking space per ADU, bringing the total to three spaces for a property.

• Milford, CT: Waives additional parking requirements for ADUs. Milford explicitly rejected new parking mandates.

• Branford, CT: Requires parking unless integrated into the existing structure.

Town-By-Town Overview: Who Allows What?

🗺️ Where can I legally build an ADU in Connecticut? This table offers a quick comparison.

Town regulations change regularly, and unfortunately there's no single source that supplies updated information from each individual town. However, we've put together an updated list, as the regulations have been adopted. Here is a preview of some key examples, with lists of which towns have opted into PA 21-29 in Connecticut:

Town	ADUs Allowed?	Detached?	Opted Out of 21-29?	Notable Restrictions
Cheshire	Yes	Yes	No	Owner occupancy; design review
New Haven	Yes	Yes	No	Encourages near transit; reduced setbacks
Orange	No	No	Yes	Local ordinance prohibits ADUs
Hamden	Yes (Limited)	Yes	No	Only in select zones; design approval
Guilford	No	No	Yes	Zoning change rejected via opt-out
West Hartford	Yes	Yes	No	1,000 sq ft max; compatible design required

Full List of CT Towns Opting Out of PA 21-29

Andover, Ansonia, Ashford, Avon, Barkhamsted, Beacon Falls, Berlin, Bethany, Bethel, Bloomfield, Bozrah, Branford, Bridgewater, Bristol, Brookfield, Brooklyn, Burlington, Columbia, Canaan, Canterbury, Chaplin, Cheshire, Colebrook, Cornwall, Coventry, Danbury, Darien, Derby, Durham, East Hampton, East Hartford, East Haven, Easton, East Lyme, Enfield, Fairfield, Farmington Franklin, Glastonbury, Granby, Greenwich, Griswold, Hamden, Harwinton, Kent, Killingly, Lebanon, Ledyard, Lisbon, Litchfield, Lyme, Mansfield, Meriden, Middlebury, Middlefield, Middletown, Milford, Monroe, Montville, Naugatuck, New Britain, New Canaan, New Fairfield, New Hartford, New London, New Milford, Newington, Norfolk, North Branford, North Haven, Norwalk, Norwich, Old Lyme, Old Saybrook, Orange, Oxford, Plainfield, Plainville, Pomfret, Preston, Prospect, Putnam, Redding, Roxbury, Salem, Salisbury, Seymour, Sharon, Shelton, Sherman, Simsbury, Somers, South Windsor, Southington, Sprague, Stafford, Stratford, Stamford, Sterling, Stonington, Thomaston, Trumbull, Union, Wallingford, Warren, Washington, Waterbury, Watertown, West Haven, Weston, Westport, Willington, Wilton, Windsor Locks, Woodstock

Full List of CT Towns Adopting PA 21-29

Bethlehem, Bolton, Bridgeport, Canton, Chester, Clinton, Colchester, Cromwell, Deep River, Eastford, East Granby, East Haddam, East Windsor, Ellington, Essex, Goshen, Groton, Guilford, Haddam, Hampton, Hartford, Hartland, Hebron, Killingworth, Madison, Manchester, Marlborough, Morris, New Haven, Newtown, North Canaan, North Stonington, Plymouth, Portland, Ridgefield, Rocky Hill, Scotland, Southbury, Suffield, Thompson, Tolland, Torrington, Vernon, Voluntown, Waterford, Westbrook, West Hartford, Wethersfield, Winchester, Windsor, Windham, Wolcott, Woodbridge, Woodbury

Ready To Start? Let Us Build It For You!

I started Peragallo Construction to make a difference for Connecticut's homeowners: I believe in straight talk, helping people out, and bringing back a respect for solid American craftsmanship.

If you're ready to take your ADU from vision to reality, and you're nearby, we're here to help. No big, corporate remodel team, just local contractors that understand just how much it means to let someone build a piece of your home.

More Information on ADU Builds in Connecticut

Schedule an ADU Discovery Call with Peragallo (Free)

ADU FAQs

Do I need a permit to build an ADU in Connecticut?

Yes, in Connecticut, all ADUs require permits. Some towns also require zoning approval and site plans.

What’s the smallest size an ADU can be in Connecticut?

 Most towns require ADUs to be at least 300–400 sq ft. Units usually must have a kitchen, bath, and sleeping area.

Can I build an ADU in (or over) a garage or existing addition?

Yes, ADUs can be built over existing garages and additions, or onto existing parts of the structure as an addition. Attached and detatched ADUs often fall under similar regulations, but be sure to check with the building codes of your specific locale.

What inspections are required to build an ADU

Inspections vary depending on your municipality, but expect inspections for (at least) foundation, framing, plumbing, electrical, HVAC, insulation, and final occupancy.

Do ADUs in Connecticut need a full kitchen?

In Connecticut, a legal ADU must have its own kitchen, bathroom, and entrance. While you can build an ADU without these features, it's unlikely to qualify as a separate residence, and may cause other issues down the line.

Will building an ADU affect my homeowners insurance?

Building an ADU in Connecticut can absolutely affect your homeowners insurance: Increased occupancy limits and larger structures can incur additional costs, so it';s important to update your policy to keep coverage.

Do ADUs increase property taxes in Connecticut?

Yes, in Connecticut, building an ADU increases your assessed value, which raises taxes. The actual financial impact depends on a number of factors, like the Mill Rate in your municipality, local tax codes and building regulations, and more.

Can I live in an ADU and rent out my main home in Connecticut?

Yes, you can usually live in an ADU and rent the main home on the property, but only if your town doesn’t have an owner-occupancy requirement.

Can I rent out my ADU on Airbnb in Connecticut?

In Connecticut, ADUs are generally regulated similar to other rentals. Whether you can rent your ADU long-term, short-term, or at all depends heavily on your location, local regulations, and if your town allows short-term lets or has rules intended to prevent rentals, such as those passed to limit the number of Air BnBs and short-term vacation rentals. Check your town or city's municipal website for specific answers.

📚 Further Reading & Resources

• Public Act 21-29 (CT State Law): Read at CT.gov

• Havenco ADU Guides by Town: Read at HavenCo

• CTiny Homes – List of Towns Allowing ADUs: Read at ctiny.homes

• Connecticut State Department of Housing: Explore the state’s housing policies, including those related to ADUs, to understand the broader regulatory landscape. Website: Connecticut Department of Housing

• “The Accessory Dwelling Units: A Step-by-Step Guide to Design and Development”: This guide from the AARP offers practical advice on planning, designing, and building ADUs, tailored to meet the needs of homeowners and builders. Available on Amazon and local bookstores.

• The American Planning Association (APA) – ADU Resources:The APA provides resources and research on ADUs, including best practices and case studies that can be helpful for Connecticut residents. Website: APA ADU Resources

• AARP’s Guide to ADUs: AARP offers a comprehensive guide that covers the benefits of ADUs, how to navigate local regulations, and tips for planning and building ADUs. Website: AARP ADU Guide

• Local Connecticut Municipal Websites:Check your town or city’s official website for specific ADU regulations, permit requirements, and any local initiatives or incentives related to ADU development. List of CT Municipal Websites