City guide · Windsor, Connecticut

Windsor ADU regulations.

ADU zoning guide for Windsor, CT. Find out about permitted ADU types, size limits, zoning rules, and building permit process.

Last reviewed 2026-04-27

  • ADUs allowedYes — Windsor permits accessory apartments under §4.4.17 of the Zoning Regulations
  • ApprovalAdministrative zoning and building permit
  • Owner occupancyRequired

Windsor has established clear ADU guidelines that, while having specific requirements, provide a pathway for homeowners to build on their existing property. Whether you're considering a primary residence for a family member, a rental income source, or an independent square footage for your growing family, understanding the local zoning rules is essential to moving forward with confidence. We've reviewed Windsor's zoning regulations in detail and outlined the key requirements below. Rules can change, so confirm details with the Windsor Planning Department or book a free consultation with our team before starting your project.

Status

Currently allowed
Yes — Windsor permits accessory apartments under §4.4.17 of the Zoning Regulations (adopted January 11, 2022)
Form of approval
Administrative zoning and building permit (checklist-based; no special permit or public hearing) for conforming proposals
Governing ordinance section
Sections 4.4.1 and 4.4.17 of the Windsor Zoning Regulations (adopted 01/11/22), incorporating CT Public Act 21-29 HB6107
Last amended
January 11, 2022 (most recent known amendment)

Eligibility

Where ADUs are allowed

Zoning districts permitted
All residential zones (per checklist: zone designation required; zones listed include AAA, R-13, R-11, R-10, R-8, with different lot coverage standards)
Lot type / use restrictions
Single-family residential lots
Minimum lot area required
Must meet zone minimum lot size
Limit per property
1 ADU per property

Types allowed

Attached
Yes
Interior conversion
Yes
Garage conversion
Yes — total footprint of accessory structures (including garage) shall not exceed 1,000 sq ft unless otherwise permitted

Size and placement

Size limits

Maximum size — ADU
30% of the principal dwelling's habitable floor area OR 1,000 sq ft, whichever is LESS
Maximum total accessory-structure footprint on lot
1,000 sq ft (a separate accessory-structure rule, distinct from the ADU size cap)

Setbacks

Setback requirements
ADU must meet all setback requirements for the applicable zone
Specific distances
Not listed in checklist; refer to zone dimensional tables in Windsor Zoning Regulations

Rules for use

Parking

Required
Accessory apartment shall utilize the existing dwelling's driveway

Owner occupancy

Required
Yes — "Will the owner reside on the premise?" is a required Yes/No on the checklist, and compliance is mandatory
Affidavit required
Yes — "At the time of certificate of occupancy and every two years thereafter, the applicant shall present an affidavit, executed by the property owners, stating that the owner continues to reside on premise and neither dwelling unit is used for short term rentals."
Short-term rental prohibition
Neither dwelling unit may be used for short-term rentals — this is confirmed in the biennial affidavit
Caveat
The CT Affordable Homes Act (2024, effective February 2025) removes municipal authority to require owner-occupancy. Whether Windsor has amended §4.4.17 is Not confirmed — flagged — see §14.

Rental use

Long-term rental allowed
Yes
Short-term rental (Airbnb/VRBO)
Expressly prohibited — affidavit confirms neither unit is used for short-term rental
Caveat on STR prohibition
CT state law changes may affect this; confirm with P&Z.

How to apply in Windsor

Approving body
Building Department / Planning & Zoning (administrative, checklist-based)
Application type
Building permit with zoning compliance checklist; simplified site plan and floor plan required
Public hearing required
No
Required documents
Simplified site plan (property lines, structures, setbacks, utilities, parking)
Certificate of Occupancy
Required; biennial owner-occupancy and no-STR affidavit required at CO and every 2 years
Typical timeline
Administrative — typically 1–4 weeks
P&Z contact
Town of Windsor Planning & Zoning | 275 Broad Street, Windsor, CT 06095 | 860-285-1974 | https://www.windsorct.gov/263/Planning-Zoning
Contact
Windsor Planning & Zoning Department | windsorct.gov | (860) 285-1980 (per the Windsor FAQ; some older listings show 860-285-1974)

Recent and pending changes

  1. January 11, 2022
    Windsor adopted §4.4.17 Accessory Apartment provisions as part of updated Zoning Regulations in response to CT PA 21-29
  2. Post-February 2025
    CT Affordable Homes Act removes owner-occupancy and may affect STR prohibition in biennial affidavit. Whether Windsor has updated its checklist and regulations is Not confirmed.

Important details

  • Biennial affidavit: Windsor is unusual in requiring a Certificate of Occupancy affidavit AND a renewal affidavit every two years confirming owner-occupancy and no short-term rental use. The CT 2024 Affordable Homes Act may have changed what can be required, but the biennial affidavit is still on the books as of April 2026.
  • Shared driveway and utilities: The accessory apartment must use the existing dwelling's driveway and utilities (electric, gas, water) — no separate utility meters or new driveways allowed. A single mailbox is required.
  • Accessory structure total footprint cap: All accessory structures combined cannot exceed 1,000 sq ft (except per §4.5.16), regardless of whether they are used as an ADU. This limits the size of ADU that can be created through garage conversion or addition on properties with existing outbuildings.
  • Coverage varies by zone: Windsor's lot coverage maximums vary by zone: 15% (AAA and R-13), 20% (R-11), 25% (R-10 and R-8), with some zones allowing up to 30%. The ADU will count toward this coverage.
  • State law explicit reference: Windsor's checklist explicitly references CT Public Act 21-29 — meaning Windsor intended to comply with the state mandate rather than create more restrictive local rules. This is important for understanding the legal baseline if a homeowner believes Windsor is being more restrictive than allowed.

Frequently asked questions

Does Windsor allow ADUs, and what are the basic requirements?

Yes, Windsor permits ADUs with guidelines on their size and use to ensure they remain accessory to the primary residence while providing additional living space.

What are the Connecticut state baseline requirements that apply to Windsor?

Since Windsor follows Public Act 21-29, state law allows ADUs with a maximum size of 1,000 square feet or 30 percent of the primary home's floor area, whichever is smaller, with no more than one required parking space.

What independent features must an ADU have in Windsor?

A legal ADU in Windsor must have its own kitchen, bathroom, and entrance to qualify as an independent dwelling unit.

Sources (4)

More city guides

Last reviewed 2026-04-27. Local rules can change — verify the latest details with the Windsor planning department, or book a free consultation with our team before starting your project. This page is informational and is not legal advice.