Connecticut ADU Permits: The Opt-Out Map Misleads

Westport opted out of Connecticut's as-of-right accessory dwelling unit law and files more ADU permits than any other town in our Connecticut file. Hartford did not opt out, and across 8,448 records carrying work descriptions it has filed one. The opt-out map tells you which rulebook a town uses. It does not tell you where the work is, and the 2026 bill that would have erased that map died on the House calendar in April.

TL;DR

• Westport opted out of Public Act 21-29 and still leads our file with 57 ADU permits.
• Guilford stayed subject to the law and files 52, with 31 tied to septic review.
• HB 5507 would have repealed the opt-out on October 1. It never got a floor vote.
• Connecticut has no ADU permit type. These jobs hide inside work descriptions.

What did Connecticut's ADU opt-out actually do?

It moved the decision back to town hall in 115 of Connecticut's 169 municipalities, and it did not close a single market.

Public Act 21-29, passed in 2021 as substitute House Bill 6107, required municipalities zoning under Section 8-2 of the General Statutes to allow one accessory dwelling unit as of right on each lot holding a single-family dwelling. As of right means the application is reviewed against the zoning regulations without a public hearing, a variance, a special permit or any other discretionary action beyond site plan conformity. The act also carried an escape clause, codified at Section 8-2o, letting a municipality opt out of that requirement.

Opting out was deliberately hard. It took a two-thirds vote of the zoning commission after a public hearing, then a two-thirds vote of the town's highest legislative body, all completed before January 1, 2023. Most towns did it anyway. The DesegregateCT survey of all 169 municipalities found 115 opted out and 54 did not.

Here is where the reasoning usually goes wrong. Opting out did not ban accessory dwelling units. It returned the question to whatever the town's own zoning regulations already said, and most of those regulations already permitted accessory apartments in some form. The same survey found that 29 of the opted-out towns amended their ADU rules anyway, and that another 29 already had regulations partially matching the state standard. The opt-out was a fight about who writes the rule, not about whether the unit gets built.

Did the 2026 bill repealing the opt-out pass?

No. It was tabled for the House calendar on April 15, 2026 and never voted on.

This matters more than it should, because a large amount of currently published guidance says otherwise. House Bill 5507 of the 2026 session, titled An Act Promoting the Development of Accessory Dwelling Units, would have extended the as-of-right ADU law to every municipality including those that previously opted out, prohibited owner-occupancy and deed-restriction requirements, required regulations to permit units of at least 400 square feet, and directed the Department of Housing to create a pre-approved ADU design program. Its stated effective date was October 1, 2026.

The bill history is short and unambiguous:

Date	Action
March 5, 2026	Referred to Joint Committee on Planning and Development
March 13, 2026	Joint Favorable Substitute, 12 yea to 9 nay
March 30, 2026	Favorable report, House Calendar Number 214
April 13, 2026	Appropriations Joint Favorable
April 15, 2026	Tabled for the calendar, House

Nothing after that. The General Assembly adjourned sine die on May 6, 2026, and no public act number was ever assigned. October 1, 2026 is 34 days away and it is not a Connecticut ADU deadline.

If you sell into this market, that gap is worth knowing about before a homeowner brings it up. A contractor who can say plainly that the opt-out repeal did not pass, and that the town's own rule still governs, is more useful than one repeating a search result.

Which Connecticut towns actually file ADU permits?

Two of them, and their legal status points in opposite directions.

Our Connecticut file holds 28,541 permit records across 51 towns and all eight counties. Searching work descriptions for accessory dwelling, ADU, accessory apartment, in-law and related phrasing returns 116 records. They are not spread evenly.

Town	Opted out of PA 21-29	ADU records	Records with descriptions
Westport	Yes	57	5,000 of 5,012
Guilford	No	52	5,024 of 5,044
Hartford	No	1	8,448 of 9,030
Bridgeport	No	0	0 of 7,483

Read the first two rows together. Westport is on the opted-out list and produces the most ADU permits in the state file. Guilford stayed subject to the law and produces almost as many. If the opt-out were a demand signal, those two numbers would not sit next to each other.

Hartford is the sharper case. It never opted out, so an accessory dwelling unit is available as of right there, and it carries more permit records with work descriptions than any other town we hold. One of them mentions an ADU. Legal permission and homeowner appetite are separate variables, and in Connecticut the second one tracks lot size, septic capacity and shoreline property values far more closely than it tracks a 2022 town meeting.

Bridgeport cannot be read at all. It carries zero work descriptions across all 7,483 records, which is a known limit of that town's file and the reason it appears here with a zero rather than a count. Its ADU activity is unmeasurable from this data, not absent.

Volume is modest and steady rather than spiking. Across the twelve months from September 2025 through August 2026, Westport and Guilford filed 67 ADU records between them, running between three and eleven per month with a May 2026 peak. That is a real, repeating stream in two towns, not a boom.

What work follows an ADU building permit?

Electrical, then plumbing, then alarm, and in Guilford the health department gets there first.

An accessory dwelling unit is a complete second dwelling with its own cooking facilities. That definition is why it generates more downstream trade work than an addition of the same square footage: it needs a kitchen, at least one bathroom, its own circuits, its own heating and often its own smoke and carbon monoxide detection integrated back into the main house system.

The permit trail shows it. Westport's 57 ADU records split by type:

Permit type	Westport ADU records
Building	37
Electrical	13
Plumbing	4
Fire alarm	3

Twenty of those 57 are not the building permit. They are the trades filing after it, and the descriptions are as blunt as they get. One Westport electrical record reads, in full, that the job is to wire the ADU. A plumbing record lists one full and one half bath, kitchen sink, laundry, an outdoor shower and gas piping for a boiler and stove. A fire alarm record describes detection in an ADU integrated into the main house system.

Guilford's file runs the other way. Fifty of its 52 ADU records are building permits, and 31 of them carry septic, soil testing or health department language. Guilford is a shoreline town on private septic, and Connecticut sizes a leaching field by bedroom count, so adding a one-bedroom ADU to a three-bedroom house is a septic question before it is a construction question. Several Guilford records are soil tests and engineered system installs whose health comments name the ADU explicitly. Not one Westport ADU record mentions septic.

The same phrase in a work description is therefore describing two different sales. In Guilford it is a septic installer lead that surfaces months before anyone frames a wall. In Westport it is a finish-trade and kitchen and bath lead on a project already under way.

What can this data not tell you?

Four limits, and the first two shape every number above.

Connecticut carries no project cost on any record and no latitude or longitude, so nothing here sizes an ADU job or maps one. Contractor names appear on close to 1% of Connecticut records, which means this file identifies the property and the work, not the firm that won it. Owner names run about a third.

Work descriptions cover roughly 72% of the Connecticut file and only from January 2025 forward. Every ADU count in this article is a description search, so it can only find what a town wrote down. A town that types a permit accurately but describes it as "residential addition" is invisible to this method, and Bridgeport, with no descriptions at all, is invisible entirely.

The 116 records are also a small number, and small numbers move. Treat the Westport and Guilford patterns as demonstrated for those two towns over 2025 and 2026, and as a hypothesis anywhere else. The 47 remaining towns in our file mostly hold a few weeks of August 2026 records, which is why Essex shows two ADU records and no conclusion follows from it.

Finally, opt-out status came from a 2023 survey, not from a state registry, because Connecticut never required towns to report the decision. A town's current ADU rule lives in its own zoning regulations and should be checked there before anyone quotes a homeowner on setbacks or size limits.

How should you target Connecticut ADU work?

Rank towns by filings, search descriptions rather than types, and split your pitch by what the town's soil does.

Start from the permit file rather than the legal map. The opt-out list is 115 towns long and tells you nothing about where accessory dwelling units are actually being built. Two towns hold 109 of the 116 ADU records we can see, and one of them is on the opted-out list. That inversion is the whole point.

Then search on description text. Connecticut has no ADU permit type and never will, because permit categories are administrative and vary town by town, which is the same reason permit type identifies the town rather than the trade across this entire file. Accessory dwelling unit work lands under building, electrical, plumbing and fire alarm, so a type filter finds a fraction of it and a description search finds the rest.

Watch the follow-on filings, not only the building permit. The electrical and plumbing permits on an ADU arrive after the shell decision, when the general contractor is actively sourcing trades and a homeowner is making finish choices. That is a shorter, warmer window than the original building permit, and it is the reason to work the file continuously rather than pulling it once. The general version of that discipline sits in reactive versus planned permit lead scoring.

Split the pitch geographically. Septic-town ADUs and sewer-town ADUs are different jobs at different stages, and Guilford and Westport prove the split inside one 116-record sample. For anyone underwriting the unit as rental income rather than building it, the real estate investor view of the same filings is a separate read on the same record.

How permits.llc fits in

We hold 28,541 Connecticut permit records across 51 towns and all eight counties, and every count in this article came out of that file, including both tables.

A permit is a signal about the homeowner, not the contractor. A Guilford homeowner who ordered a soil test in June because the health department needed a bedroom count for a one-bedroom accessory unit has already decided to build. The building permit is months out, the electrician is further out than that, and the decision is already made. Whether Guilford opted out of Public Act 21-29 changes none of it.

Pull the file and run the description search against your own towns at the Connecticut permit download. To see where the depth sits before committing a territory, browse Connecticut coverage by county, and if you would rather have new filings arrive than go looking for them, permit alerts will send them as they land. The wider territory logic for this state is in the Connecticut 169-town map.