ADU Laws in Connecticut (2026)
Connecticut state ADU law details, key provisions, preemption status, and recent legislative changes for accessory dwelling units.
Law Name
Connecticut Public Act 21-29 — An Act Concerning Zoning and Affordable Housing
Effective Date
2021-07-01
Preempts Local Ordinances
Yes — state law overrides local restrictions
Has State Law
Yes
Key Provisions
Requires municipalities to permit accessory dwelling units as of right in all residential zones
Municipalities may not prohibit ADUs on owner-occupied single-family residential lots
ADUs must be permitted ministerially — no discretionary review or public hearing required
Local regulations may set reasonable development standards (setbacks, size limits, design) but may not effectively prohibit ADUs
Municipalities have authority to regulate maximum size of ADUs — typically limited to a percentage of primary dwelling floor area
Owner-occupancy of either the primary or accessory unit may be required by local ordinance
ADUs may be attached or detached from the primary dwelling
Municipalities that did not adopt compliant ADU ordinances by a certain deadline are subject to state override
Legislative History
2021 — PA 21-29
Required all Connecticut municipalities to permit ADUs by-right on owner-occupied single-family lots in residential zones. Municipalities must adopt local ADU ordinances compliant with state law. Eliminated the ability of towns to ban ADUs outright in residential zones.
Official Sources
What Does Preemption Mean for Local Cities?
Because Connecticut law preempts local ordinances, individual cities cannot impose restrictions stricter than the state standard. A city may still have additional administrative requirements, but cannot deny ADU applications that comply with state minimums.
Learn about Connecticutzoning preemption →Source: Connecticut Public Act 21-29 — An Act Concerning Zoning and Affordable Housing. Last verified April 5, 2026. View source