ADU Pass
Garfield County
ADU Pass helps homeowners in Garfield County, Montana navigate the permit paperwork for building an accessory dwelling unit. We cover 6 cities and 6 ZIP codes in this county.
Map
County ADU details
County ADU ordinance
Garfield County (Jordan county seat; northeast-central Montana; ~1,300 residents across 4,668 sq mi - one of the most sparsely populated counties in the lower 48 with population density well under one person per square mile; badlands and Missouri River breaks terrain dominated by the Charles M. Russell National Wildlife Refuge and the Upper Missouri River Breaks National Monument; Hell Creek Formation badlands have produced some of the most significant Cretaceous dinosaur fossils ever discovered, including the type specimen of Tyrannosaurus rex) does not maintain a comprehensive countywide zoning code. Land use in Garfield County is essentially unregulated by the county itself; oversight comes from federal land management (BLM Upper Missouri River Breaks NM, USFWS Charles M. Russell NWR, US Army Corps of Engineers Fort Peck Reservoir), state-level subdivision review under the Montana Subdivision and Platting Act (MCA Title 76 Ch. 3), and state-level building, sanitation, and water-rights oversight. Garfield County contains NO incorporated cities or towns - Jordan, the county seat, is a Census-Designated Place (~340 residents) and is unincorporated. As a result, Montana SB 528 (2023, Mont. Code Ann. § 76-2-345) HAS NO APPLICATION in Garfield County: SB 528 preempts MUNICIPAL ADU restrictions for incorporated cities, and Garfield County has none. ADU construction proceeds under state-level oversight only.
State-floor overlay: Montana SB 528 establishes a state ADU floor for incorporated cities ONLY. Garfield County has NO incorporated cities, so SB 528 has no application here. ADU permissibility is determined by state-level oversight only (subdivision review, septic, well, floodplain, building code where applicable).
Adopting body: Garfield County Board of County Commissioners (no zoning ordinance; commissioners administer subdivision, floodplain, and roads only)
County permitting (unincorporated parcels)
Garfield County issues no countywide building permits for residential construction; like nearly all sparsely populated eastern-Montana counties, building-code enforcement is delegated to the State of Montana (Department of Labor & Industry, Building Codes Bureau) only for certain commercial or state-jurisdiction projects. Single-family residences and ADUs in Garfield County are typically constructed without municipal-style plan review. State-level oversight applies to on-site septic (DEQ Subdivision review for parcels created after 1973) and well construction (DNRC water rights). Floodplain development requires a permit through the county floodplain administrator under MCA Title 76 Ch. 5 - applicable along the Missouri River corridor (Fort Peck Reservoir backwater) and Big Dry Creek. Note: SB 528 has NO application here since Garfield County contains no incorporated cities. Note: Federal land use (BLM Upper Missouri River Breaks NM, USFWS Charles M. Russell NWR) is governed by federal management plans; private parcels adjacent to federal land may face access, water-rights, and ESA-compliance considerations (especially for sage grouse, prairie-fish, paddlefish, and pallid sturgeon habitat).
Impact fees: Garfield County levies no impact fees of any kind. Note: SB 528's prohibition on ADU-specific impact fees has no application here since SB 528 only reaches incorporated municipalities and Garfield County has none.
County assessor
Property assessment in Montana is centralized at the Montana Department of Revenue (DOR), not the county. The Garfield County DOR field operations are administered through the Lewistown / Miles City regional offices. ADU additions are captured as improvements to the host parcel on the next biennial residential reappraisal cycle - capture is delayed by the absence of a county building department feeding shared permit data. Mont. Code Ann. § 15-6-134 establishes Class 4 residential property and taxable-value calculation. MCA § 15-6-222 establishes a homestead exemption for principal residences. Montana operates on a two-year reappraisal cycle for residential property under MCA § 15-7-111. Garfield County property values are among the lowest in Montana on a per-parcel basis but ranch tracts span thousands of acres; agricultural class rates (under MCA § 15-7-201 et seq.) dominate the county tax base.
Assessment policy: Improvement value for an ADU is added to the parcel record on the next biennial revaluation. Without a county building department, capture relies on field discovery, satellite imagery, or owner self-report - delays of 2-4 years are common. Montana applies a residential class rate (Class 4, currently ~1.35% of market value, adjusting per legislative session) to compute taxable value. Homestead / principal-residence treatment under MCA § 15-6-222 (and HB 231 2025 adjustments) shields the existing structure but new improvement value is fully captured. Appeals run first to the Garfield County Tax Appeal Board (CTAB) and then to the Montana Tax Appeal Board.
County overlays (5)
Garfield County's overlay landscape is dominated by federal land management - the Charles M. Russell National Wildlife Refuge and the Upper Missouri River Breaks National Monument together occupy a large fraction of the county's area, with associated ESA Section 7 considerations for sage grouse, paddlefish, pallid sturgeon, and other listed species. FEMA NFIP floodplain regulation applies along the Missouri River corridor (Fort Peck Reservoir backwater) and Big Dry Creek. Wildland-Urban Interface considerations are present but limited - the county is largely treeless prairie and badlands rather than forested. There are no county-administered historic-district overlays. No tribal trust lands lie within Garfield County (the Fort Peck Indian Reservation borders to the northeast in Roosevelt and Valley Counties; Northern Cheyenne and Crow Reservations are far to the south).
- FEMA NFIP Special Flood Hazard Areas - Missouri River / Fort Peck Reservoir backwater, Big Dry Creek — Most of Garfield County's habitable parcels sit on uplands away from SFHAs; floodplain compliance is a localized concern affecting a small fraction of county parcels. Fort Peck Reservoir is managed by the US Army Corps of Engineers; Corps-managed shoreline easements and access agreements apply to lakefront parcels.
- Wildland-Urban Interface - limited; mainly grass/sage rather than forest — No county WUI ordinance; voluntary defensible-space practice recommended around any forested parcels. Insurance underwriters increasingly price wildfire risk into premiums but Garfield County's grass-fire profile is closer to standard than to the catastrophic crown-fire profiles of the western Montana mountain zones.
- Charles M. Russell National Wildlife Refuge (USFWS) - federal land management overlay — CMR NWR adjacency drives some of the most distinctive ADU economics in Garfield County - hunting/wildlife outfitters and limited tourism create niche short-term-rental demand around Jordan and the Hell Creek area, but baseline residential demand remains very low.
- Upper Missouri River Breaks National Monument (BLM) - federal land management overlay — Monument-adjacent ADUs face access constraints typical of remote BLM-adjacent parcels. River-corridor private inholdings carry premium recreation value.
- No tribal trust land within Garfield County
Known county issues (4)
- other — ADU construction is regulatorily simple but distinct from the SB 528-driven ADU rights elsewhere in Montana. Builders should not rely on SB 528 framing in marketing or permit narrative for Garfield County parcels.
- other — Total ADU project budget should account for substantial logistics premium. Self-build / owner-build is more common here than in any other Montana county.
- other — Cash and conventional-financed ADU projects on private parcels face minimal federal-overlay friction. Federally-financed ADU projects on federal-adjacent parcels can face significant timeline impact.
- other — Garfield County ADU projects face minimal regulatory cost but maximum construction-quality variance. Resale and refinancing may be constrained by lack of permit history.
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.