ADU Laws in Connecticut (2026)
Connecticut state ADU law details, key provisions, preemption status, and recent legislative changes for accessory dwelling units.
Law Name
Effective Date
2021-07-01
Preempts Local Ordinances
Yes — state law overrides local restrictions
Has State Law
Yes
Statewide ADU Preemption Applies
State law establishes statewide preemption standards that supersede local regulations. The citation and source below confirm the verified legal basis.
Key Provisions
Requires municipalities to permit accessory dwelling units as of right in all residential zones · Source
Municipalities may not prohibit ADUs on owner-occupied single-family residential lots · Source
ADUs must be permitted ministerially — no discretionary review or public hearing required · Source
Local regulations may set reasonable development standards (setbacks, size limits, design) but may not effectively prohibit ADUs · Source
Municipalities have authority to regulate maximum size of ADUs — typically limited to a percentage of primary dwelling floor area · Source
Owner-occupancy of either the primary or accessory unit may be required by local ordinance · Source
ADUs may be attached or detached from the primary dwelling · Source
Municipalities that did not adopt compliant ADU ordinances by a certain deadline are subject to state override · Source
Legislative History
2021 — Connecticut PA 21-29 · Source
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. · Source
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