Olmsted County, MN Accessory Structures: ADU Rules (2026)

Olmsted County zoning is administered under Chapter 1400 (County Zoning Ordinance) pursuant to Minn. Stat. Ch. 394 (county planning and zoning enabling act). The Olmsted County Planning Department administers zoning for unincorporated areas and the four contracting townships of Eyota, Marion, Oronoco, and Quincy; other townships and the City of Rochester operate their own ordinances. In the County's R-1 (Single Family Residential) district, accessory buildings must be at least 6 feet from the principal dwelling, 5 feet from side property lines, and 8 feet from rear lot lines, with no individual accessory building exceeding 1,000 square feet. The City of Rochester regulates ADUs through the Unified Development Code (UDC) Section 60.300.020G, which became effective January 1, 2023. Under the UDC, ADUs are an allowed accessory use in all residentially zoned districts. Each lot may contain no more than one ADU, and an ADU must not exceed 1,000 sq ft of gross floor area. Detached ADUs are limited to the rear or side yard and must be architecturally compatible with the principal dwelling. The City also operates an ADU Pilot Program offering up to $20,000 in fee/cost reimbursements for qualifying property owners. Minnesota has no statewide ADU preemption statute - the 2024 omnibus housing legislation expanded various housing tools but did not impose a uniform ADU mandate, leaving local zoning authority intact under Minn. Stat. §394.25 (county) and §462.357 (city).