ADU rules in Hamden

Section 620(a) expressly allows an accessory dwelling unit 'detached from the proposed or existing principal dwelling and located on the same lot as such dwelling.' Detached units became legal on 12-1-2022 through Zoning Text Amendment #22-989; the pre-2022 text had barred them outright ('No accessory building shall be used or created for the purpose of accommodating an Accessory Apartment'). Table 6.1 lists the Section 620 use as 'P' (Zoning Permit) in the R-1, R-2, R-3, R-4 and R-5 zones and in the T2, T3, T3.5, T4 and T5 transect zones, so no hearing is involved. On a lot not served by both public sewer and public water the lot must be at least 6,000 sq ft or the zone minimum, whichever is greater.

The same sentence in Section 620(a) allows the unit to be 'attached to or located within the proposed or existing principal dwelling,' which covers additions and interior conversions alike. Section 620(h) confirms that 'Expansion of a principal dwelling shall be permitted to accommodate an Accessory Apartment via dormer(s) or an addition beyond the existing foundation.' Two conditions bite on interior conversions: Section 620(e) bars a unit in a garage or basement 'unless one wall opens to grade, and contains a window,' and Section 620(g) forbids any exterior change to the existing front of the principal dwelling except dormers or windows. Section 620(f) also requires the unit to be self-contained with its own separate entrance and cooking, sanitary and sleeping facilities.

Section 620(c) sets 'a minimum floor area of 300 square feet, maximum floor area of not less than 30% of the principal dwelling unit or 1,000 square feet, whichever is less, and a maximum of 2 bedrooms.' The 30-percent-or-1,000 formula was copied from the state floor in CGS 8-2o(a)(3) when the town rewrote the section in 2022; before that the cap was a flat 600 sq ft. The 300 sq ft minimum and the two-bedroom ceiling are purely local: the Town Planner's 11-22-2022 memo lists both among 'the provisions in the existing regulations that are not addressed by Public [Act] 21-29, Section 6.' The regulations impose no separate ADU height limit, so the underlying zone's building standards govern.

Section 620(d) requires that 'One of the occupants of either the Principal or Accessory Dwelling Unit shall be the owner of record for the lot.' The owner may live in either unit, and this is an ongoing occupancy condition, not merely a test at application. The Commission adopted this exact wording on 11-15-2022 after Commissioner McDonagh moved to incorporate a resident's suggested clarification. The requirement survives state law twice over: CGS 8-2o(a)(6) never listed owner occupancy among the things a town may not require, and Hamden in any event opted out of 8-2o. Enforcement is loose in practice: at the 12-5-2022 committee meeting the Town Planner acknowledged the town 'can't really keep track of relatives/family members' and that 'owner of record is in existing regulations.'

Zoning Text Amendment #26-1004, adopted 6-23-2026 with an effective date of 7-1-2026, rewrote both parking tables to say there is 'No minimum requirement for <16 units' (Table 5.5, replacing the residential rows) and '*No minimum parking requirement for developments that have <16 units' (new footnote to Table 3.1, transect zones). A single-family house plus one accessory dwelling unit is well under that threshold, so no space is required anywhere in town. Until 6-30-2026 Table 5.5 required '1 space per dwelling unit' for a Single-Family Accessory Dwelling Unit in the R zones, and Table 3.1 required 2.0 spaces per dwelling unit in T2, T3 and T3.5, 1.5 in T4 and 1.0 in T5. The change tracks state law: CGS 8-2(d)(9), as rewritten by Nov. Sp. Sess. P.A. 25-1 S. 18 effective 7-1-2026, now forbids zoning regulations to 'Require a minimum number of off-street motor vehicle parking spaces for any residential development except as provided in section 8-3n.' CGS 8-3n (S. 19, also effective 7-1-2026) permits a minimum only for a development of more than sixteen dwelling units, or inside up to two locally adopted conservation and traffic mitigation districts, and independently bars any zoning enforcement officer or commission from rejecting a residential application 'solely on the basis that such development fails to conform with any requirement for off-street motor vehicle parking spaces' absent a finding of a specific adverse impact on public health and safety that cannot be mitigated by conditions. Hamden has adopted no conservation and traffic mitigation district, so both the local tables and state law point the same way for an ADU. Separately, the old parking opt-out route is gone: CGS 8-2p was repealed effective 1-1-2026 by P.A. 25-1 S. 53, so no municipality can opt back into higher per-unit minimums.

Section 620 allows an accessory dwelling unit 'in any zone permitting a single-family residence subject to a Zoning Permit,' which is Hamden's staff-level ministerial approval. Table 6.1 marks the Section 620 use 'P' in R-1 through R-5 and in T2, T3, T3.5, T4 and T5; the table's legend reads 'P - Zoning Permit, S - Site Plan Application, SP - Special Permit Application, Blank Space - Not Allowed,' so no Commission hearing, site plan review or special permit is triggered. That standing was reconfirmed when Zoning Text Amendment #26-1004 reprinted the residential block of Table 6.1 effective 7-1-2026 and left the Section 620 row unchanged. The separate regime in Section 620.1 (dwelling units accessory to a non-residential use) does require a Special Permit in the T-3.5 zone.

Section 620(i) states flatly that 'Accessory Dwelling Units cannot be used for short-term rentals,' a ban the Planning and Zoning Commission added in the 2022 rewrite and which CGS 8-2o(a)(7)(B) expressly preserves for municipalities. Long-term tenancy is otherwise unrestricted: nothing in Section 620 limits who may rent, for how long, or at what rent, and no familial or age test applies. The practical limit is Section 620(d), which requires the owner of record to occupy either the principal dwelling or the accessory unit, so both units cannot be rented out at once. The unit cannot be sold separately because it shares the lot with the principal dwelling. Hamden runs a Nonresident Landlord Registration Program through the Planning and Zoning Department, but by its terms it reaches nonresident landlords, which an owner-occupant of an ADU property is not.