Hill County

Hill County issues no countywide building permits for residential construction in unincorporated areas. Like most rural Montana Hi-Line counties without a full county building department, 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 unincorporated Hill 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 Milk River, Beaver Creek, and other Hi-Line drainages. Havre and Hingham operate their own town permitting processes inside their limits. The Rocky Boy's Indian Reservation operates under tribal land-use authority and federal HUD/BIA permitting; county and state permitting do not reach reservation parcels. Hill County is in IECC climate zone 6B (Hi-Line plains; harsh winter winds; ground snow loads 30-50 psf typical at the plains, 60-90 psf in the Bear's Paw foothills approaching the reservation).

Impact fees: Hill County and its towns levy no impact fees. SB 528 prohibits ADU-specific impact fees in Havre and Hingham; neither has a general residential impact-fee schedule.

Property assessment in Montana is centralized at the Montana Department of Revenue (DOR), not the county. The Hill County DOR field operations are administered through the Great Falls / Havre regional office. 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. Hill County reservation land (Rocky Boy's, ~74,000 acres) is federal trust land and not on the county tax rolls. Off-reservation Hi-Line agricultural land carries Class 3 agricultural assessment under MCA § 15-6-133, providing significant tax relief versus residential classification.

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, owner self-report, or town-permit feeds (Havre / Hingham) - delays of 1-3 years are common. Montana applies a Class 4 residential rate (~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 Hill County Tax Appeal Board (CTAB) and then to the Montana Tax Appeal Board.

Hill County's overlay landscape is dominated by tribal sovereignty and Hi-Line geography: (1) The Rocky Boy's Indian Reservation - ~74,000 acres of sovereign Chippewa Cree tribal land covering the dominant southern half of Hill County including most of the Bear's Paw Mountains - county zoning, county permitting, and state property tax do not apply within reservation boundaries; tribal land-use code governs. (2) FEMA NFIP floodplain along the Milk River corridor (the Hi-Line spine through Havre), Beaver Creek, Big Sandy Creek, and other Hi-Line drainages. (3) Wildland-Urban Interface in the Bear's Paw Mountains (most of which lies within the reservation but a thin slice is off-reservation). (4) Historic-district overlays at Fort Assiniboine NHL (a 19th-century military post south of Havre) and the H. Earl Clack Memorial Museum / Havre downtown. (5) BNSF Railway mainline corridor through Havre (a major division point) - rail-adjacent setbacks and noise considerations apply.

• Rocky Boy's Indian Reservation (Chippewa Cree Tribe) — ADU work on tribal trust land follows BIA leasing under 25 CFR 162, tribal land-use code, and HUD-184 financing. Section 184 Indian Home Loan Guarantee is the dominant federal financing pathway. Free-of-county-permit but subject to tribal review and BIA approval where federal trust status applies. STR economics on reservation are modest; the dominant ADU use case is multi-generational family housing.
• FEMA NFIP Special Flood Hazard Areas - Milk River, Beaver Creek, Big Sandy Creek — Spring snowmelt and ice-jam events drive flooding peaks, especially on the Milk River. Lower Beaver Creek through Beaver Creek Park (the largest county park in the United States) is a popular STR/recreation corridor. New ADUs in mapped SFHA must be elevated to or above the Base Flood Elevation; elevation cost can add $15,000-$30,000 in this market.
• Wildland-Urban Interface - Bear's Paw Mountains (off-reservation slice) — Hi-Line plains carry low forest-fuel load; WUI hazard is concentrated in the Bear's Paw foothills. Insurance markets are stable for plains-level Hi-Line parcels; foothill parcels face moderate underwriter caution.
• Fort Assiniboine NHL; Havre Downtown / H. Earl Clack heritage corridor — ADU work on Havre NRHP-listed contributing properties triggers SHPO consultation only if federal financing or permitting (FHA, USDA RD, HUD-184) is involved. Fort Assiniboine ADU adjacency is rare given the federal-lease status and reservation-boundary geography.
• BNSF Railway Hi-Line mainline corridor / Havre division point — Rail-adjacent ADU economics in Havre are constrained by noise; underwriting on rail-adjacent residential is conservative. Hi-Line CDPs (Inverness, Kremlin, Rudyard, Gildford) sit immediately adjacent to the mainline in their cores - the dominant rural housing pattern on the Hi-Line.