City guide · Westport, Connecticut

Westport ADU regulations.

ADU zoning guide for Westport, CT. Learn about zoning eligibility, ADU types, size limits, and Connecticut ADU regulations.

Last reviewed 2026-04-27

  • ADUs allowedYes
  • ApprovalBy-right via administrative Zoning Permit for detached ADUs meeting all standards
  • Max size65,340 sq ft
  • Owner occupancyRequired

Westport 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 Westport's zoning regulations in detail and outlined the key requirements below. Rules can change, so confirm details with the Westport Planning Department or book a free consultation with our team before starting your project.

Status

Currently allowed
Yes
Form of approval
By-right via administrative Zoning Permit for detached ADUs meeting all standards; Special Permit required for conversions of existing accessory buildings/structures exceeding the size/height standards listed in §11-2.4.8A
Governing ordinance section
§11-2.4.8A, Accessory Dwelling Unit; §11-2.4.12A, Accessory Apartment contained in the principal building
Last amended
Text Amendment #853 (June/July 2025) — requires 10-foot minimum separation between ADU and principal structure. Text Amendment #865 (proposed 02/24/2026, public hearing 03/30/2026) — status: pending adoption as of April 2026.

Considering an ADU in Westport? Book a free consultation — we’ll watch for ordinance updates and walk through your options.

Eligibility

Where ADUs are allowed

Zoning districts permitted
All zoning districts (Text Amendment #791 permitted ADUs on lots in any zoning district)
Lot type / use restrictions
Single-family lots. ADUs are detached accessory structures. Interior accessory apartments (§11-2.4.12A) are governed by a separate regulation
Limit per property
One ADU per lot

Types allowed

Detached
Yes — this is the primary ADU type regulated under §11-2.4.8A (standalone backyard structure)
Attached
Conditional — if contained within or attached to the principal dwelling, it is regulated as an Accessory Apartment under §11-2.4.12A (up to 1,500 sq ft or 25% of dwelling, whichever is less) (addition to main house)
Interior conversion
Yes — regulated as Accessory Apartment under §11-2.4.12A (basement, attic, garage interior)
Garage conversion / detached accessory conversion
Conditional — existing accessory buildings/structures exceeding the size or height standards may be converted to an ADU by Special Permit from the Planning & Zoning Commission. ADU constructed above a detached garage: permitted, with the garage building area allowed to exceed the maximum ADU building area so long as the ADU itself does not exceed the maximum

Size and placement

Size limits

Maximum sq ft (by lot size)
Lots up to and including 1.5 acres (65,340 sq ft): 850 sq ft maximum building area for ADU
Interior Accessory Apartment (§11-2.4.12A)
Up to 1,500 sq ft or 25% of the principal dwelling's gross floor area, whichever is less
Maximum height
Main roof slope ≥ 6:12: 26 feet

Setbacks

Front, side, rear setbacks
ADU must meet all setback, coverage, grading, drainage and other requirements applicable to the property in the zoning district
Distance from primary structure
Minimum 10 feet between the ADU and the principal structure (excluding a covered pedestrian connection), per Text Amendment #853 adopted June 2025
Coverage / open space requirements
ADU building area counts toward building and total coverage requirements (subject to pending #865 which would remove the 350 sq ft coverage exemption)

Rules for use

Parking

Required spaces
At least 3 off-street parking spaces must be on the lot in total (for both the principal dwelling and ADU combined); proof of adequate parking must be submitted to the P&Z Office
Exemptions
None specified

Owner occupancy

Required
This is an active legal question. Westport's regulations historically included owner-occupancy requirements; however, the CT Affordable Homes Act (2024, Section 7, effective February 2025) removes municipalities' ability to enforce owner-occupancy for ADUs. A Westport Zoning Board discussion in August 2024 confirmed the board acknowledged the new state law removes this ability.
Specifics
As of April 2026, the current §11-2.4.8A text (through Text Amendment #853) does not appear to retain an owner-occupancy requirement. No primary source found confirming the exact current text on this point post-February 2025.

Rental use

Long-term rental allowed
Yes
Sale of ADU separately from primary
No — ADU is an accessory structure; cannot be subdivided or sold separately

How to apply in Westport

Approving body
Planning & Zoning Department (Zoning Permit for conforming ADUs); Planning & Zoning Commission for Special Permit applications
Application type
Administrative Zoning Permit for compliant detached ADUs; Special Permit for conversions of existing oversized/non-standard structures
Public hearing required
No for Zoning Permit; yes for Special Permit
Other inspections / certificates required
Health district (Westport-Weston Health District) approval for septic systems if not on town sewer; proof of sewer hookup if on town sewer
P&Z contact
PandZ@westportct.gov | 203-341-1030 | 110 Myrtle Avenue, Room 203, Westport, CT 06880

Recent and pending changes

  1. June/July 2025
    Text Amendment #853 adopted — introduced mandatory 10-foot minimum separation between ADU and principal structure.
  2. 2023
    Text Amendment #825 — increased ADU building area from 650 sq ft to 850 sq ft for lots under 1.5 acres; clarified roof height rules.
  3. February–April 2026 (pending)
    Text Amendment #865 — proposed to remove the 350 sq ft coverage exemption for lots up to 1.5 acres. Public hearing held 03/30/2026. Not yet adopted.

Important details

  • Detached vs. interior ADU governed by different regulations: §11-2.4.8A covers detached ADUs; §11-2.4.12A covers accessory apartments within the principal building (up to 1,500 sq ft or 25% of dwelling). A homeowner must identify which type they are building.
  • ADU above detached garage is permitted: A detached garage may exceed the maximum building area to accommodate an ADU above it, as long as the ADU footprint itself stays within the maximum.
  • Flood zone ADUs: Any ADU in the Special Flood Hazard Area must comply with §31-11 floodplain regulations; no additional building height permitted for flood-compliance purposes.
  • Historic structures: The dimensional standards may be modified for applications approved under §32-18 (Historic Residential Structures), which may allow larger or differently configured ADUs on historic properties.
  • ADUs do not help meet 8-30g affordable housing threshold unless deed-restricted to affordable rents — Westport does not require this.
  • The 10-foot minimum separation between an ADU and the principal structure was added by Text Amendment #853 (effective July 2025).
  • Pending Text Amendment #865 (proposed February 2026) would remove the 350 sq ft coverage exemption for lots up to 1.5 acres. Not yet adopted.
  • The Westport Zoning Board acknowledged in August 2024 that the CT Affordable Homes Act 2024 limits the town's ability to enforce its owner-occupancy requirement — pending formal amendment.

Frequently asked questions

Can I build a detached ADU in Westport, and if so, how tall can it be?

Yes, detached ADUs are permitted in AAA, AA, and R-3 zones. Maximum height is 16 feet to the peak if the roof pitch is 6:12 or lower, or 26 feet to the peak if the roof pitch exceeds 6:12.

What are the occupancy limits for an ADU in Westport?

Standard ADUs are limited to a maximum of 2 occupants, or 3 people if the ADU is designated as affordable housing. The owner must reside in either the principal dwelling or the ADU. Note: this 2/3-person cap is referenced in older Westport materials but has not been confirmed in the most recent §11-2.4.8A text — verify directly with Westport P&Z before relying on it.

What is the minimum rental term allowed for an ADU in Westport?

The shortest term that an ADU can be rented for is 6 months, which restricts short-term vacation rentals or Airbnb-style arrangements. Note: the 6-month minimum is referenced in older Westport materials — confirm directly with P&Z that this rental-term floor still applies under the most recent text amendments.

Sources (8)

More city guides

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