ADU rules in Hartford

Hartford's form-based Zoning Regulations list Accessory Dwelling Unit as an accessory use permitted subject to use-specific conditions (◐) in the MX-1, MX-2, NX-#, N-#-1, N-#-2 and N-#-3 districts, which are exactly the six districts where a One-Unit Dwelling is itself permitted outright. Section 3.4.2 B. defines that symbol as "permitted by right in the districts in which they are listed," so there is no hearing. Section 3.5.1 A.(3) lets the unit sit "in a detached accessory structure or outbuilding" or in the principal structure, so a backyard cottage or garage conversion is squarely allowed. The lot must contain one, and no more than one, residential structure occupied as a one-unit dwelling, and no property may hold more than one ADU. A detached unit also has to meet the accessory-structure rules of 4.20: side or rear yard only, no closer to the front lot line than the house, 5-foot side and rear setbacks, and only one out building per lot in an N or NX district.

The same provision allows the accessory dwelling unit to be located "in a principal structure," which covers basements, attics, additions and internal conversions, on the same as-of-right footing as a detached unit. The 12-13-2022 text amendment loosened this considerably: it struck the former requirement that an internal ADU have "a separate entrance to the exterior or to an unconditioned porch type space" and the requirement that a detached ADU occupy a structure formerly used as a garage or barn. Two conditions still shape an internal unit: section 3.5.1 A.(6) requires that its exterior entrance not be visible from the front right of way and prohibits a separate numeric address, and section 3.5.1 A.(7) bars a new separate utility connection unless the lot already had more than one connection when the application was filed.

Section 3.5.1 A.(4) caps the ADU at the lesser of 1,000 square feet or 50 percent of the principal dwelling unit's usable floor area, and expressly excludes exterior patios, decks, porches and staircases that provide interior access between the two units. "Usable floor area" is defined in section 1.6 as floor area within the outside walls of a residential building with at least 7 feet of floor-to-ceiling clearance, excluding unfinished cellars, unfinished basements, unfinished attics, garages, open porches and accessory buildings. Hartford's 50 percent share is more generous than the floor CGS 8-2o(a)(3) sets, which is 30 percent of the principal dwelling's net floor area or 1,000 square feet, whichever is less. A detached unit is separately limited in height: accessory structures default to 15 feet under 4.20.2 E., while an out building under 4.20.3 C.(2) may instead be one story lower than the principal building.

Nothing in section 3.5.1 A. or anywhere else in the Zoning Regulations requires the owner to live on the property in order to have or rent an accessory dwelling unit; a full-text search of the regulations turns up owner-residency rules only for bed and breakfasts (3.3.1 B.), home occupations (3.5.1 C.(3)(g)) and short-term room rentals in the N-#-1 districts (3.5.1 E.(3)). Subsection 3.5.1 A.(8) now reads simply "Reserved" because the 12-13-2022 amendment repealed the old 7,500 square foot minimum lot size, which its own explanation described as bringing the regulations "in line with the State statutes Public Act 21-29." This matters because CGS 8-2o does not prohibit municipal owner-occupancy mandates: they are absent from the (a)(6) list of forbidden requirements, so towns are free to impose them. Hartford simply chose not to.

Section 3.5.1 A.(5) says parking for the ADU "must be provided on-site in accordance with the requirements of these regulations as they apply to 2-Unit Dwellings," but that cross-reference resolves to nothing, because Hartford has no parking minimums. Figure 7.2-A is titled "Maximum Parking Requirements" and has only two columns, uses and maximums, and section 7.2.2 B. states that the column "indicates the maximum number of off-street parking spaces allowed." For a 2-Unit Dwelling the ceiling is 2 spaces per unit. Bicycle parking carries "No minimum requirement" for one-, 2- and 3-unit dwellings under Figure 7.2-B. The one real limit is that section 3.5.1 A.(5) allows no additional curb cuts beyond those the building type and district already permit. Because the city requires zero spaces, the CGS 8-2o(a)(6)(C) ceiling of one space for an accessory apartment never binds here, and the separate CGS 8-2p parking opt-out is no longer live law in any event: Nov. Sp. Sess. P.A. 25-1, S. 53 repealed 8-2p effective 1-1-2026, and S. 18 rewrote CGS 8-2(d)(9) effective 7-1-2026 to bar any minimum number of off-street parking spaces for residential development except as S. 19 allows for developments of more than sixteen dwelling units, which only reinforces Hartford's existing zero-minimum posture.

Review is administrative. Section 3.4.2 B. provides that accessory uses marked ◐ "are permitted by right in the districts in which they are listed, provided that they comply with the use-specific conditions of 3.5," and the special permit path in 3.4.2 C. does not apply to accessory dwelling units in any district. Section 3.5.1 A.(1) requires the property owner to file a zoning permit for the unit before it is recognized as an ADU, and under section 1.3.2 C.(1) the Planning and Zoning Commission has delegated zoning permit decisions to the zoning administrator, who retains discretion to refer an application to the full commission. Municipal Code section 35-2 sets the fee for accessory uses and accessory structures not requiring site plan review at $100.00. Because the use is as of right, CGS 8-2o(b) gives the city 65 days to decide.

An accessory dwelling unit is a dwelling unit, and because Hartford imposes no owner-occupancy or minimum-lease term, it may be rented long-term. The city's rental licensing program reaches only housing containing three or more housing units, so a single-family house plus one ADU falls below the threshold (Municipal Code section 18-20 A.). Zoning does cap who may live there: section 3.5.1 A.(9) limits the ADU at any one time to one adult plus that adult's related minor children, or two adults in total plus minor children related to at least one of them, so three unrelated adults cannot share the unit. Renting the whole unit for short stays is governed by Room Rental - Short Term (3.5.1 E.): no more than 21 cumulative days in any 6-month period and no more than 3 such rentals per 6 months, with a zoning permit that expires in 3 years and can be revoked for nuisance, plus a property manager living or working within 10 miles outside the N-#-1 districts. A special permit is required to exceed those limits. CGS 8-2o(a)(7)(B) expressly preserves that municipal power over short-term rentals.