- Owner occupancyRequired
Trumbull, CT permits accessory apartments under Article II, Section 1.2.2.7 of the Zoning Regulations. The unit must be attached to the principal dwelling and is capped at 30 percent of the principal's livable floor area, with a 300 square foot minimum. Trumbull opted out of Connecticut's Public Act 21-29 and applies its local rule. Most ADU applications require a Special Permit from the Planning and Zoning Commission, except for cases that fit entirely within the existing footprint without exterior changes, which the Zoning Enforcement Officer can approve administratively.
Status
- Adoption status
- Active. Article II Section 1.2.2.7 of the Trumbull Zoning Regulations.
- Governing ordinance
- Trumbull Zoning Regulations, Article II, Section 1.2.2.7 (Temporary In-Law and Accessory Apartments)
- Key differentiator
- Each accessory apartment is treated as an affordable housing unit under CGS 8-30g, with rental rate caps and a 40 year deed restriction.
Eligibility
Where ADUs are allowed
- Zoning districts permitted
- Residential zones (specific zone codes not enumerated in Section 1.2.2.7; broadly applicable across residential districts)
- Lot type
- Single family residential lots
- Limit per property
- One accessory apartment per lot
Types allowed
- Attached ADU (within or adjoining principal)
- Yes
- Basement Accessory Apartment
- Yes (defined sub-type)
- Detached ADU
- Prohibited. May not be located in a detached or accessory building.
- External appearance
- House must keep external appearance of a single family residence; no additional front entrances
Size and placement
Size limits
- Minimum sq ft
- 300 sq ft of livable floor area
- Maximum percentage
- 30 percent of the principal dwelling's livable floor area
Setbacks
- Setback requirements
- Apartment is interior to the existing house; underlying zone setbacks apply to the principal structure
Rules for use
Parking
- Total parking required
- At least 4 off street spaces combining the principal dwelling and accessory apartment
Owner occupancy
- Required
- Yes. At least one dwelling unit in the converted single family home must be owner occupied.
- Notarized letter
- Owner submits a notarized letter committing to occupy one of the units, with bona fide temporary absences permitted
Rental use
- Affordable housing deemed status
- Each accessory apartment is deemed an affordable housing unit under Connecticut General Statutes Section 8-30g
- Deed restriction
- 40 year deed restriction recorded on the Trumbull Land Records
- Utility metering
- Utilities may not be billed separately from the main unit
How to apply in Trumbull
- Default
- Special Permit from the Planning and Zoning Commission under Article XV
- Administrative path
- If proposal is entirely within the existing footprint and there are no exterior changes other than a door or steps, the Zoning Enforcement Officer can approve
- Application materials
- Certified plot plan, Town Sanitarian sign-off on septic and water, floor plan at 1/4 inch equals 1 foot scale
- Contact
- Trumbull Planning and Zoning Department
Important details
- Affordable housing tie-in: Each Trumbull accessory apartment is deemed an affordable housing unit under CGS 8-30g, capping rental rates at the state's affordability standard.
- 40 year deed restriction: Recorded on the Trumbull Land Records as part of the Special Permit conditions.
- Attached only: Detached ADUs and standalone backyard cottages are prohibited under Section 1.2.2.7.
- Administrative path for in-footprint conversions: Pure interior conversions with no exterior changes (other than a door or steps) can be approved by the Zoning Enforcement Officer without a Special Permit hearing.
Frequently asked questions
Can I build a detached ADU in Trumbull?
No. Section 1.2.2.7 explicitly states that an accessory apartment may not be located in a detached or accessory building. The unit must be attached to the principal dwelling, with an internal connecting door, and the house must keep its single family appearance from the outside.
Why is my Trumbull ADU treated as affordable housing?
The local ordinance ties accessory apartments to Connecticut General Statutes Section 8-30g. Each unit is deemed an affordable housing unit, with rental rates capped at the state's affordability standard and a 40 year deed restriction recorded on the Land Records. This applies whether you intend to rent the unit or use it for family.
Do I need a Special Permit?
Usually yes. Most accessory apartment applications go before the Planning and Zoning Commission for a Special Permit under Article XV. The exception is when the conversion is entirely within the existing footprint with no exterior changes other than a door or steps; those cases can be approved administratively by the Zoning Enforcement Officer.
Sources (3)
Last reviewed 2026-04-28. Local rules can change — verify the latest details with the Trumbull planning department, or book a free consultation with our team before starting your project. This page is informational and is not legal advice.