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

Significant Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Olmsted County, MN, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Form allowed: mobile home only
Approval required: conditional use permit
A-1 farm-labor condition: 80-acre farm threshold
A.R.C. minimum lot: 35 acres
Qualifying grounds: health care, age 60+, farm work, ownership

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Minnesota under recent ADU streamlining laws. The Olmsted County, MN rules below cover local size, height, and setback requirements.

Summary

Olmsted County doesn't allow garage apartments or backyard ADUs by right on its farm lots; a second dwelling on an agricultural lot is only permitted as a mobile home, approved as a conditional use, and only when the household meets one of four narrow family or farm-labor conditions.

These county ordinances apply to unincorporated areas of Olmsted County. Incorporated cities within the county may have their own rules that take precedence over county-level regulations.

1. One mobile home as a second dwelling on a lot, under one or more of the following circumstances. a) When there is a need to provide services to residents of either of the dwellings for reasons of physical or mental condition; or b) When all adult residents of either of the dwellings are sixty (60) years of age or older; or; c) When at least one of the adult occupants of each dwelling is employed at least seasonally in general farming activities carried out on the parcel; or d) When at least one of the adult occupants of each dwelling has at least a partial ownership interest in the parcel.

View official code

Full Breakdown

" The four qualifying circumstances are a documented need for one household to provide care to the other for physical or mental health reasons; all adult residents of either dwelling being 60 or older; at least one adult occupant of each dwelling working at least seasonally in general farming on the parcel; or at least one adult occupant of each dwelling holding a partial ownership interest in the parcel. C. 06(D)(8)). 02, which reviews traffic, drainage, and compatibility with neighboring property before granting the permit; there is no administrative or by-right path to add a second residence, garage apartment or accessory dwelling unit to a lot in these districts.

Violations & Fines

Placing a second mobile home, or any second dwelling, on an A-1 or A.R.C. lot without an approved conditional use permit is a zoning violation. Ch. 1400 § 3.10 makes any violation of the ordinance a misdemeanor, with each day the unpermitted dwelling remains occupied treated as a separate offense, on top of any order to remove the structure.

Frequently Asked Questions

Can I build a garage apartment or granny flat on my Olmsted County farm lot?

Not as a stand-alone accessory structure. The zoning ordinance only allows a second dwelling on an A-1 or A.R.C. lot in the form of a mobile home, approved case by case as a conditional use, and only when the household meets one of the ordinance's listed family, age, or farm-labor conditions.

What conditions qualify for a second mobile home dwelling in the A-1 district?

Section 5.00(B)(1) lists four: a documented health care need between the two households, all adult residents of either home being 60 or older, at least one adult in each home working seasonally in farming on the parcel, or at least one adult in each home holding a partial ownership interest in the land.

Is the process different in the Agricultural Residential Cluster District?

Yes. Section 5.06(D)(8) requires the cluster lot to be at least 35 acres and narrows the qualifying conditions to three: health care need, both households being 60 or older, or full-time farm employment on the parcel, rather than the four broader conditions available in A-1.

Sources & Official References

[1]Olmsted County Code of Ordinances, Chapter 1400 Zoning Ordinance

Other rules in Olmsted County

Shed & Carport RulesSome Restrictions Noise Ordinances: Decibel LimitsSome Restrictions Parking Rules: Abandoned VehiclesSignificant Restrictions Parking Rules: Loading ZonesSome Restrictions Parking Rules: Commercial & Oversized VehiclesSome Restrictions Parking Rules: Driveway RulesSome Restrictions Animal Ordinances: Veterinary Clinic ZoningLight Restrictions

All Olmsted County rules

How Olmsted County compares: Easiest Cities to Build an ADU·Compare Olmsted County to another location·View the Minnesota accessory structures overview

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