ADU rules in Winooski

A detached backyard ADU is a permitted use on any lot developed with a single-unit dwelling, and one accessory dwelling is allowed per lot. Section 5.1.A covers units 'located within or appurtenant to a single-unit dwelling', and the Section 2.4 land use table marks Accessory Dwelling Unit as P/CU in Residential A, Residential B, Residential C, and the Central Business (C-1) district; Appendix B (Gateway form-based code) Part 8 also lists Accessory Dwelling as a household living use subject to Section 5.1. A detached ADU is treated as an accessory structure: 10 ft front, 5 ft side, and 5 ft rear setbacks in the residential districts, and up to 20 ft tall. On a lot that already holds two to four units, a detached ADU is still available but only through conditional use review by the Development Review Board (Section 5.1.C), which also requires that all existing units sit in one building and none of them is already an accessory dwelling.

Section 5.1.A defines an ADU as a distinct unit 'located within or appurtenant to a single-unit dwelling', so a basement conversion, an internal unit, or an addition qualifies on the same permitted-use terms as a detached cottage, with no separate standard for attached units. Article IX's definition of Accessory Dwelling is equally broad. Site plan review is expressly waived for accessory dwellings under Section 2.3.C, so an internal conversion normally clears with a zoning permit alone. The one place attachment matters is the multi-unit path: Section 5.1.C.6 requires that an ADU added to a two- to four-unit property be detached from the multi-unit building, so an internal unit carved out of an existing duplex or triplex is not available under that route.

Section 5.1.B.4 caps a permitted-use ADU at 30 percent of the total habitable floor area of the single-unit dwelling or 900 gross square feet, whichever is greater, which mirrors the state definition at 24 V.S.A. 4303(38)(B) and therefore cannot be tightened. On the conditional-use path for two- to four-unit properties, Section 5.1.C.5 measures the 30 percent against the average total habitable floor area of the existing dwelling units. Height is the other binding number: note 4 to the Section 2.5 dimensional table lets an ADU rise to 20 feet unless the primary structure would permit greater height, which is more generous than the ordinary accessory-structure rule (75 percent of the principal structure, never less than 10 or more than 25 feet). The building still has to fit the residential districts' 50 percent maximum lot coverage and the accessory-structure setbacks of 10 ft front, 5 ft side, 5 ft rear.

Vermont removed owner occupancy from the statewide ADU mandate in 2026. Act 179 (S.328), signed June 18, 2026 and effective July 1, 2026, struck the words 'on an owner-occupied lot' from 24 V.S.A. 4412(1)(E), so no bylaw may exclude as a permitted use one ADU within or appurtenant to a single-family dwelling regardless of who lives there. Winooski's printed ULUDR has not caught up: Section 5.1.B.1 still lists 'The property is owner occupied' as a condition of the permitted-use path, and Article IX still defines Owner-Occupied as the owner maintaining principal residency year-round. The city has said on the record that it will not apply it. At the July 13, 2026 City Council public hearing the Director of City Planning reported that the state 'removed the owner occupancy requirements for accessory dwelling units' and that 'State statutes supersede our regulations so we won't be adhering to the owner occupancy requirement that currently exists here'; the Section 5.1 amendment was pulled from the adopted package and sent back to the Planning Commission for redrafting. Note also that even under the unamended text, the Section 5.1.C conditional-use path never required owner occupancy.

The Section 4.12.C minimum vehicle parking table lists Accessory Dwelling Unit (ADU) at 1.0 space per dwelling unit, the same ratio as any other residential unit, and Section 5.1.B.5 makes meeting Section 4.12 a condition of the permitted use. That single space is the statewide ceiling as well: 24 V.S.A. 4414(4) bars a municipality served by municipal sewer and water from requiring more than one parking space per dwelling unit, and Winooski is fully served. Section 4.12 does not apply at all in the Downtown Core district. The reduction incentives in Section 4.12.E (underground parking, EV charging) are aimed at larger projects and will rarely help a single ADU; there is no by-right transit-proximity waiver.

For the ordinary case, a homeowner with a single-unit dwelling, an ADU is a permitted use decided administratively by the Zoning Administrator. Section 5.1.D requires a zoning permit for any ADU, the Section 2.4 legend defines 'P' as permitted by right requiring only administrative approval where no dimensional relief is sought, and Section 2.3.C exempts accessory dwellings from site plan review. Expect a 17 to 30 day appeal period after approval. The use table shows 'P/CU' because a second, discretionary route exists: if the property does not satisfy Section 5.1.B (most often because it already holds two to four units), Section 5.1.C sends the application to the Development Review Board for a conditional use hearing under Section 6.7. Separate Public Works approvals for the water service and sewer connection run alongside the zoning permit.

Nothing in the ULUDR limits who may occupy an ADU or bars renting it long term, and with the state's 2026 repeal of the owner-occupancy condition an ADU can be a straightforward rental unit. Renting it does trigger the Public Building Registry: Chapter 17 requires a yearly registry filing and a Certificate of Fitness before occupancy, on a four-year inspection cycle. Short-term rentals are legal but licensed. Chapter 17 Article V, adopted February 20, 2024 and effective July 1, 2024, requires a city STR license for any unit rented for stays under 30 consecutive days totaling more than 14 days in a rolling year; each unit needs its own license, licenses expire every June 30, and the license number must appear on every public listing. Fees are $250 per unit per year owner-occupied and $1,400 non-owner-occupied. Since July 1, 2025 the number of non-owner-occupied STR licenses is capped, and City Council Resolution of June 16, 2025 set that cap at 50, first come first served with a waitlist. Operators also need a Vermont Meals and Rooms license unless their platform remits the tax.