ADU rules in Waterbury

Waterbury permits no detached accessory dwelling unit. Section 4.06.03 bars more than one principal residential building on a lot in a Residential District except by Special Permit or Special Exception, and adds a flat rule that no building to be used as a dwelling may be constructed or moved to the rear of another building on the same lot, which forecloses the backyard-cottage layout outright. The Master Use Table in Section 4.08 has no accessory dwelling unit or accessory apartment category at all, and Section 4.04 provides that uses not listed are not permitted. This is a deliberate policy, not an oversight: Waterbury opted out of the statewide CGS 8-2o accessory apartment mandate by a Zoning Commission vote on August 24, 2022 and a Board of Aldermen vote on September 19, 2022, both before the January 1, 2023 cutoff in 8-2o(f), and the Commission's resolution states that 'the City's current policy of not allowing Accessory Dwelling Units (ADUs) best serves the City's interests.'

There is no attached, basement or internal accessory apartment use in Waterbury either. Adding a second dwelling unit inside a house does not create an accessory unit under these regulations; it converts the building to a 'Two or Three Family Residence,' a separate principal use on the Master Use Table. That conversion is not available in the RS-12, RS and RL single-family districts, where the two/three family row is marked SP* with the footnote 'two family only, permitted in conjunction with a Planned Residential Conservation Development.' It is available in the RM, RH and RO districts by Zoning Permit under Section 10.02.02, but subject to the district's minimum lot area, its frontage rule (the greater of 60 feet or 25 feet per dwelling unit with exterior access) and its density cap (24 units per acre in RM, 42 in RH, 8 in RO), which is a change of principal use rather than an ADU right. Because the city opted out of CGS 8-2o in 2022, the statute's command that attached and interior accessory apartments be allowed as of right does not reach Waterbury.

Because Waterbury allows no accessory dwelling unit, it publishes no ADU floor-area or height cap. The nearest limits are the accessory-structure standards in Section 4.02.02, which apply to sheds, detached garages and similar buildings: no accessory building on a lot with no principal building, none in a required front or side yard, at least 5 feet from side and rear lot lines and 10 feet from the principal building, no more than 25 percent of the required rear yard occupied by all accessory buildings combined, no below-grade space except for a swimming pool, and no free-standing accessory building over 15 feet in height. For comparison, had the state floor applied, CGS 8-2o(a)(3) would have required an allowance of at least the lesser of 30 percent of the principal dwelling's net floor area or 1,000 square feet; the 2022 opt-out removed that floor.

There is no ADU owner-occupancy rule to report because Waterbury permits no accessory dwelling unit, so the Zoning Regulations contain no ADU occupancy provision. This is not a preemption question in any event: CGS 8-2o never prohibited owner-occupancy requirements, since they are absent from the list of forbidden conditions at 8-2o(a)(6). Waterbury does regulate rental ownership generally rather than occupancy: Code of Ordinances Section 160.06 requires any nonresident owner of residential rental property or a dwelling unit to file and keep on file with the Town Clerk a current residential address, or the address of an agent in charge if the owner is an entity.

Table 2 in Section 9.03.05 requires 1.5 parking spaces per dwelling unit for single family, two/three family and multifamily residences alike, and exempts CBD uses so long as no existing on-site parking is removed. Two 2026 state changes overtake that text. CGS 8-2(d)(9), rewritten by Nov. Sp. Sess. P.A. 25-1, S. 18 effective July 1, 2026, now bars zoning regulations from requiring a minimum number of off-street parking spaces for any residential development except as provided in CGS 8-3n, and 8-3n allows minimums only for residential developments containing more than sixteen dwelling units, capped at one space per studio or one-bedroom unit and two per larger unit or a lower parking-needs-assessment figure, while forbidding rejection of a residential application solely for parking nonconformity absent a specific adverse public health and safety impact that conditions cannot mitigate. Waterbury's 2022 parking opt-out no longer supplies an escape: CGS 8-2p, the opt-out mechanism the Zoning Commission and Board of Aldermen used on August 24 and September 19, 2022 (PL 2022-0235), was repealed effective January 1, 2026 by P.A. 25-1, S. 53. Waterbury has adopted neither of the two 'conservation and traffic mitigation districts' that 8-3n(d) would let it use to keep minimums for smaller projects, so its 1.5-space standard is effectively enforceable only against residential developments over sixteen units, and then only up to the statutory cap.

There is no ADU permit path to classify, because no accessory dwelling unit use appears on the Master Use Table. For context on how Waterbury reviews housing generally: uses marked ZP are acted on administratively by the Zoning Enforcement Officer under Section 11.03, uses marked SP go to the Zoning Commission and uses marked SE to the City Plan Commission under Section 11.04, and Section 11.03.01 requires a Zoning Permit for any new principal structure, any addition of residential units, any expansion of 50 percent or more of a principal structure's gross living area, and any change of use. A homeowner adding a second unit in RM, RH or RO therefore proceeds through the Zoning Permit route for a Two or Three Family Residence, not through an ADU permit.

The Master Use Table's use definitions list 'accessory room rental of not more than 2 non-transient roomers or boarders' among the as-of-right accessory uses of a Single Family Residence, so taking in a lodger is allowed even though creating a separate dwelling unit is not. Short-Term Lodging, defined as facilities offering transient lodging where the average length of stay is less than 60 days, is a distinct principal use permitted by Zoning Permit only in the RO, CO, CA, CG and CBD districts, so whole-house short-term rentals are not a permitted use in the RS-12, RS, RL, RM or RH residential districts, and the city runs no separate short-term rental licensing program. Nonresident owners of residential rental property must register a current address or agent in charge with the Town Clerk under Code of Ordinances Chapter 160, with civil penalties of up to $250 for a first violation and $1,000 for later ones. CGS 8-2o(a)(7)(B) expressly preserves municipal power to prohibit or limit short-term rental use of accessory apartments in any case.