ADU Pass
Baker
ADU Pass helps homeowners in Baker, Fallon County, Montana navigate the permit paperwork for building an accessory dwelling unit. This area covers 1 ZIP code.
Map
Fallon County — county ADU rules and overlays
County ADU ordinance
Fallon County (Baker county seat; far southeastern Montana on the North Dakota line; ~3,000 residents — one of the smallest counties by population in the state) does not maintain a comprehensive countywide zoning code. Fallon County operates under Montana's permissive default for rural counties: parcels in unincorporated territory have no county-imposed zoning unless a special zoning district has been formally created under MCA Title 76, Chapter 2, Part 1 (county zoning) or Part 2 (planning-and-zoning districts). Montana SB 528 (MCA § 76-2-345) preempts municipal zoning to require ADUs by-right inside city limits — but only Baker is incorporated in Fallon County, with population under 1,800 (well below SB 323's 5,000-resident duplex-preemption threshold). SB 528 ADU preemption applies to Baker as a city of any size; SB 323 duplex preemption does NOT (Baker is below the 5,000 threshold). For unincorporated parcels, the only land-use constraints are typically subdivision review under the Montana Subdivision and Platting Act, on-site sewage rules under MCA Title 75 Ch. 5, and any voluntary covenants on the parcel. An ADU on an unincorporated Fallon County parcel is generally permissible without county zoning approval, subject to building-code (state-adopted IRC) compliance and septic permitting through the local sanitarian. Oil and gas development is the major non-ADU land use in the county (eastern edge of the Cedar Creek Anticline / Baker oilfield; older legacy field with continued production but not Bakken-scale activity).
State-floor overlay: Montana SB 528 (MCA § 76-2-345) establishes a state floor for ADU permissibility in incorporated cities; the county's lack of a comprehensive zoning code in unincorporated territory means ADUs face no county zoning bar there.
County regulatory overlays
Fallon County's overlay footprint is light. FEMA NFIP floodplain along Sandstone Creek, Beaver Creek, and the Little Missouri River drainage tributaries is the dominant mapped overlay, but the prairie / shortgrass terrain keeps SFHA areas narrow. No WUI designation has been formally adopted; grassland fire risk is real but not codified at the county level. No coastal or seismic overlays. Oil and gas activity in the Cedar Creek Anticline imposes setback considerations from active wellbores under Montana Board of Oil and Gas Conservation rules but does not directly regulate residential or ADU construction.
- FEMA NFIP Special Flood Hazard Areas - Sandstone Creek, Beaver Creek — SFHA areas are narrow on the prairie. A new ADU in a mapped SFHA must be elevated to or above the Base Flood Elevation; impact varies but is generally lower-cost than river-bottom counties.
- Grassland and prairie fire risk areas — No WUI permit required, but voluntary defensible-space practices recommended.
- Oil and gas wellbore setbacks — Severed mineral estates are common; mineral owner has access rights to the surface for development but new residential buildings can constrain pad placement. Confirm chain of title.
County permitting (unincorporated parcels)
Fallon County does not operate a county building department. Montana law does not require small rural counties to administer the building code, and Fallon County (population ~3,000) has not opted in. For unincorporated parcels, building permits are generally not required by the county for residential construction outside any formally-created zoning district. The state-adopted Montana Building Code (based on IBC/IRC) applies as a technical floor, but enforcement in counties without a building department falls back to the State Building Codes Bureau on complaint or to point-of-sale inspection requirements from lenders and insurers. The single permit most likely to be required for an ADU is the on-site wastewater (septic) permit issued by the County Sanitarian under MCA Title 75 Ch. 5 and ARM Title 17 Ch. 36. Subdivision review by the County Planning Office applies if the ADU project requires creating a new parcel; placing an ADU on an existing parcel does not normally trigger subdivision review.
Montana state — ADU law and programs
State ADU law
Montana has enacted strong statewide ADU preemption through Senate Bill 528 (2023), codified at Mont. Code Ann. § 76-2-345. SB 528 is part of the 2023 'Montana Miracle' housing reform package (also including SB 323 duplex preemption and SB 245 commercial-zone multifamily). SB 528 requires every Montana city to allow at least one ADU by right on any lot containing a single-family dwelling, with size capped at the lesser of 1,000 sq ft or the floor area of the primary dwelling. ADUs may be attached, detached, or internal. Cities are prohibited from requiring additional parking, fees, design-match to the primary dwelling, owner-occupancy, occupant-relationship limits, or impact fees specifically for ADUs. ADUs must still meet building, fire, and public-health codes. Effective 2024-01-01. The Montana Supreme Court (September 2024) lifted a Gallatin County district-court injunction obtained by Montanans Against Irresponsible Densification (MAID), allowing the law to take effect; a Daily Montanan March 2025 ruling confirmed the affordable-housing bills are a 'legitimate government concern.' The 2025 session continued the reform trajectory (HB 533 wildfire-insurance transparency); no rollback bills have advanced as of 2026-04-26.
State HOA preemption
Montana's HOA statute Mont. Code Ann. § 70-17-901 (https://mca.legmt.gov/bills/mca/title_0700/chapter_0170/part_0090/section_0010/0700-0170-0090-0010.html) prohibits an HOA from adopting or enforcing a covenant amendment that imposes more onerous use restrictions than those in place when a member acquired their interest, unless the affected member consents in writing. After 2019-05-09, an HOA also may not enforce a covenant in a way that limits uses that were allowed when the member acquired the property. This is a one-way ratchet protecting existing uses, not an affirmative ADU preemption: an HOA's pre-existing covenant prohibiting ADUs remains enforceable against owners who took title with that restriction in place. SB 528's text expressly addresses municipal zoning, not private covenants, and § 70-17-901(2) carves out covenants required to comply with applicable federal, state, and local laws — but a covenant banning ADUs is not 'required' by SB 528, so the carve-out does not flip pre-existing ADU bans. A homeowner subject to an HOA covenant prohibiting ADUs has no state-law remedy under current Montana law and must seek the consent or amendment process within the association.
State financing programs
Montana Board of Housing (MBOH) under the Montana Department of Commerce does not operate an ADU-specific loan or grant product as of 2026-04-26. Construction or rehab of an ADU on a primary residence may be financed indirectly through MBOH's Regular Bond Loan Program (30-year, low-interest first mortgage geared to first-time buyers under income and purchase-price limits) or the Bond Advantage / MBOH Plus Down Payment Assistance Programs (up to 5% / $15,000 in DPA). All MBOH first-mortgage products require qualifying for an underlying FHA, VA, RD, or HUD-184 loan; an existing ADU on the property is generally permissible. The Department of Commerce's Coal Trust Multifamily Loan Program funds rental housing developments which can include ADU-style units in multi-unit projects but is not a homeowner-facing instrument.
State housing programs
Montana does not operate a statewide pre-approved ADU plan catalog as of 2026-04-26. The 2023 Montana Miracle reform package (SB 528, SB 323, SB 245, SB 382) established the country's most aggressive state preemption of single-family-only zoning, but did not pair the preemption with a state plan library, impact-fee waiver fund, or per-ADU rebate. SB 382 (the Montana Land Use Planning Act, https://archive.legmt.gov/bills/2023/BillPdf/SB0382.pdf) restructures comprehensive-planning requirements for cities of 5,000+ residents toward a more streamlined, plan-then-permit model. Implementation by the Department of Commerce and the Department of Environmental Quality continues; the DEQ Energy Code office published an ADU best-practices guide in fall 2023.
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.
ZIP Code
- 59313
Post Office
- 130 S 1st St W, 59313