ADU Zoning

Which zones allow ADUs:

ADUs are allowed in residential zoning districts R-2, R-1, R-1/2, R-1/3, or R-1/5. A single ADU may be established on any lot with an existing or proposed single-family dwelling.

What types of ADUs are allowed:

Attached or Detached.

What are the size/floor area requirements:

Maximum ADU sizes and floor area

• 700 square feet if part of or attached to the principal dwelling.
• 1,000 square feet if detached and separate from the principal dwelling.
• Less than 30 percent of the total finished floor area of the principal dwelling plus the ADU.

How many parking spaces:

Darien requires one parking space for a studio or one bedroom and one additional parking space for each additional bedroom in the ADU.

What are the rental requirements:

Long-term and short-term rentals that are greater than 90 days are allowed.

Owner-occupancy is required.

What about utilities, sewer or septic:

Utilities and sewer tie into the main house. Septic is job-specific. New and separate utilities are allowed.

Which zones allow ADUs:

Attached ADUs: Permitted as an accessory use in Single-Family Residence Districts (AAA, AA, R-3, R-2, and A) and Multi-Family Residence Districts (B and C).

Detached ADUs: Permitted as an accessory use only in Single-Family Residence Districts AAA, AA, and R-3.

What are the size/floor area requirements:

The ADU cannot exceed 40% of the originally existing residence's floor area or 1,500 square feet, whichever is less.

How many parking spaces:

At least one off-street parking space is required specifically for the ADU.

What are the rental requirements:

Neither the primary house nor the ADU can be rented for a period of less than 60 consecutive days.

Occupancy is limited to a maximum of two persons, unless the unit is contracted as “affordable housing,” in which case up to three persons may occupy it.

A principal owner (holding at least 50% interest) must reside in either the primary dwelling or the ADU for the duration of the permit.

What about utilities, sewer or septic:

If public water and sewer are unavailable, private systems must be approved by the Department of Health. The unit must comply with all housing, building, fire, and health codes.

Which zones allow ADUs:

In RA-4, RA-2, RA-1, R-20, R-12, and R-7 zones, both detached and attached ADUs are allowed. There is no minimum lot size requirement for ADUs.

What types of ADUs are allowed:

Attached, Detached, or Converted ADUs

What are the size/floor area requirements:

The maximum floor area for detached ADUs is 700 sq. ft., but this can be increased to 800 sq. ft. if there is a demonstrable need.

Accessory Apartments shall not exceed 1,200 square feet in floor area or 35% of the primary home’s square footage, whichever is less. Max Height is 25 feet.

How many parking spaces:

Greenwich requires one parking space per Accessory Apartment. If you plan to add an ADU to a Greenwich property, plan to accommodate three parking spaces within the bounds of your property.

What are the rental requirements:

Long-term and short-term rentals are allowed.

Owner-occupancy is required.

What about utilities, sewer or septic:

Utilities and sewer tie into the main house. Septic is job-specific.

Which zones allow ADUs:

All zones for single-family dwellings.

What types of ADUs are allowed:

Attached, Detached, or Converted ADUs

What are the size/floor area requirements:

Detached accessory dwelling units shall not exceed 700 square feet in floor area.

Attached accessory dwelling units shall not exceed 1,000 square feet in floor area.

What is the max height:

15 feet when located 20 feet or less from a side or rear property line;

20 feet when located more than 20 feet from a side and rear property line.

How many parking spaces:

Norwalk requires one parking space for the ADU. If you plan to add an ADU to a Norwalk property, plan to accommodate three parking spaces within the boundary of your property.

What are the rental requirements:

Owner-occupancy is required and the tenant has a minimum six-month rental agreement.

What about utilities, sewer or septic:

Utilities and sewer tie into the main house. Septic is job-specific.

Which zones allow ADUs:

All single-family residential zones provided the lot meets the minimum size requirement for that specific zone.

What types of ADUs are allowed:

Attached or Detached ADUs.

What are the size/floor area requirements:

Detached Units: For lots 1.5 acres or smaller, the maximum footprint is 650 square feet, with 350 square feet not counted toward coverage. For lots larger than 1.5 acres, the maximum footprint is 1,000 square feet, with no deductions.

Attached Units: The accessory apartment’s floor area cannot exceed 1,500 square feet or 25% of your primary home’s total square footage, whichever is smaller. The allowed floor area is based on the size of your primary residence and property.

How many parking spaces:

Westport requires one parking space for the ADU. If you plan to add an ADU to a Westport property, plan to accommodate three parking spaces within the boundary of your property.

What are the rental requirements:

Owner-occupancy is required and only long-term rentals are permitted.

What about utilities, sewer or septic:

Utilities and sewer tie into the main house. Septic is job-specific.