ADU rules in Burlington

A detached backyard unit is allowed and is reviewed by staff. In the Residential Low and Residential Medium districts a lot may hold one principal structure plus one detached secondary structure, an allowance that took effect November 1, 2024 under Sec. 4.4.5(e). Where the principal structure is an owner-occupied single detached dwelling, adding one unit in a detached secondary structure is expressly routed to administrative review and exempted from impact fees under Sec. 4.4.5(d)4.D. Residential High and Residential Corridor set no cap on the number of structures on a lot, and Sec. 5.1.2(c) permits more than one principal structure in a residential district subject to Sec. 4.4.5. Burlington repealed its stand-alone accessory dwelling unit section effective July 15, 2025, so a backyard unit is now measured against ordinary residential district standards rather than ADU-specific ones.

An interior or attached unit is a permitted use, not a special category. Table 4.4.5-2 allows up to four dwelling units per structure in Residential Low and Residential Medium, and Appendix A lists duplexes and multi-unit dwellings of three or more units as permitted in all four residential districts. Converting a basement, attic, or addition into a second unit at an owner-occupied single detached dwelling is sent to administrative review and exempted from impact fees under Sec. 4.4.5(d)4.D. Every unit must be at least 350 square feet (Table 4.4.5-2 note 2) and must meet the Article 13 dwelling unit definition, which requires separate kitchen, bath, and living facilities.

Until July 15, 2025 the CDO capped an accessory unit at 900 square feet or 30 percent of the principal home's gross floor area, whichever was greater (old Sec. 5.4.5(a)2). ZA-25-02 deleted that section and put nothing in its place, so no percentage or square-foot ceiling applies to a second unit today. What binds now is the district massing table: in RL and RM a detached secondary structure may cover at most 1,100 square feet of ground and a principal structure 1,800 square feet, both up to 35 feet and 3 stories; RC caps principal structures at 3,600 square feet; RH sets no footprint limit and allows 50 feet and 4 stories. Lot coverage still governs total build-out at 45 percent in RL, 55 percent in RM, and 80 percent in RH and RC, and the old 650 square foot lot-coverage waiver for ADUs was deleted by the same amendment. The floor is a 350 square foot minimum dwelling unit size.

The repealed Sec. 5.4.5(b) made approval of an accessory unit contingent on owner occupancy of either unit as a primary residence, voided the permit and required removal of the kitchen within 90 days if occupancy lapsed, and forced a deed notice into the land records. ZA-25-02 deleted all of that effective July 15, 2025, and nothing in the current CDO conditions a second dwelling unit on who lives there. Owner occupancy now only buys advantages: Sec. 4.4.5(d)4.D gives an owner-occupied single detached dwelling administrative review and an impact fee exemption for one added unit, and Chapter 18 charges $80 rather than $120 per unit per year to register a rental in an owner-occupied building with two or fewer units. Short-term rental eligibility is a separate regime and does turn on primary residence.

Sec. 8.1.8 states that minimum off-street spaces are eliminated in all parking districts for all uses, with one exception for applications seeking to house more than four unrelated adults in a dwelling unit. Article 8 now sets maximums instead: Table 8.1.9-1 caps single family detached and duplex parking at 3 spaces per unit in Neighborhood districts, 2 in Shared Use, and 2 in Multimodal Mixed-Use districts. Tandem parking is allowed for every dwelling unit, and Sec. 8.1.14(c) expressly allows stacked parking for single-family detached dwellings and accessory dwelling units with no attendant. This is well below the ceiling in 24 V.S.A. § 4414(4), which forbids a municipality from requiring more than one space per dwelling unit in districts served by municipal sewer and water.

A zoning permit is required for a new unit (Sec. 3.1.2), but the administrative officer decides it, not the Development Review Board. Sec. 3.2.7(a)13 delegates creation of an accessory dwelling unit to staff wherever no other standard would require DRB review, and Sec. 4.4.5(d)4.D repeats that an added unit at an owner-occupied single detached dwelling is subject to administrative review and approval. Burlington had already removed conditional use review for ADUs in the 2020 ZA-20-03 reform, and the 2024 to 2026 Neighborhood Code amendments kept the permitted-use posture. One wrinkle: a detached second building on an RL lot triggers design review under Sec. 3.4.2(b)2.g, which adds elevations, a landscape plan, and photographs to the application, though staff still sign it off unless a conditional use, a variance, a building of three or more units, or a mapped design review area under Map 3.4.2-1 pushes it to the DRB. Expect a 15 day appeal period after approval before the permit issues.

Every rental unit must be registered with Code Enforcement and renewed annually by April 1, and must pass periodic minimum housing inspections (Ch. 18, Secs. 18-15 and 18-16). The fee is $120 per unit per year, $80 for owner-occupied dwellings with two or fewer units, with an additional $120 for a whole-unit short-term rental (Sec. 18-30). Short term rentals are a permitted use in every residential district under Appendix A footnote 33, but Sec. 18-15(f) limits a host to one registered whole-unit STR; in buildings or on lots with fewer than five dwelling units a host may register a unit as a whole-unit STR only if it is the host's primary residence or sits in the same building or lot as it. A whole-unit STR away from the host's residence is allowed only where the assessor lists the property as a seasonal home, or where the host rents another unit in the same building or lot at Article 9 inclusionary affordability or to a tenant on federal or state rental assistance. Renting one or two rooms in an owner-occupied dwelling needs neither inspection nor registration (Sec. 18-16), and converting a long-term tenancy into an STR makes the host liable for the displaced tenant's relocation costs (Sec. 18-29a(d)).