Building permits, zoning and septic rules across Montana's counties

At a glance

Residential building permits

37 counties without; 14 with limited requirements; 5 requiring them¹⁶⁷

Countywide zoning

22 counties without countywide zoning; 25 with zoning²⁸

No residential permit and no countywide zoning

19 counties meet both conditions⁹

Septic permits

Local health department drainfield permit; DEQ subdivision sanitation review where applicable³¹⁰

RV living

12 counties have an answer: 4 allowed as a county land-use matter and 8 limited; 44 unanswered⁴

Tiny homes

14 counties have an answer: 10 allowed as a county land-use matter and 4 limited; 42 unanswered⁵

Owner-builder

Contractor-license exemption for qualifying owners; applicable construction permits still apply¹¹

Domestic wells

Permit exception may apply at no more than 35 gpm and 10 acre-feet annually; Notice of Intent required before use¹²

Who to call

Contact details are copied from each office’s official page and were checked against it on October 10, 2026.

Which Montana counties don't require a residential building permit?

Montana has 37 of 56 counties without a residential building-permit requirement for unincorporated homes; city rules differ from these county counts.¹ The highest-scoring counties in that group are Lewis and Clark County, Broadwater County, Mineral County, Lincoln County, Meagher County, Glacier County, Judith Basin County, Pondera County.¹ Another 14 counties require residential building permits only in certain cases, and 5 require them.⁶⁷

Use the Montana counties without building permits list to narrow the search, but a missing residential building permit does not remove separate electrical, plumbing or mechanical permit requirements.¹¹³ In state jurisdiction, farm and ranch buildings and residential buildings containing fewer than five dwelling units are exempt from state building permits, except residential buildings serving transient guests; certified local programs have their own requirements.¹⁴ Qualifying owners have a contractor-license exemption, which does not waive applicable construction permits or inspections.¹¹

Which Montana counties have no zoning?

Montana has 22 counties without countywide zoning, including Broadwater County, Mineral County, Sanders County, Judith Basin County, Pondera County, Beaverhead County, Teton County, Fergus County.² Montana also has 25 counties with zoning.⁸ The Montana no-zoning list is a starting point for comparing those county land-use answers.²

For buyers seeking both conditions, 19 counties have neither a residential building-permit requirement nor countywide zoning; Broadwater and Mineral lead that group by Index score.⁹ See the combined no-building-permit and no-countywide-zoning list for the full group.⁹ Montana law allows county zoning for all or part of a jurisdictional area, with regulations that can differ between districts, so ask the county planning office whether the specific parcel lies in a zoning district.¹⁵ A county without countywide zoning still needs the separate drainfield and designated-floodplain checks described below.¹⁰¹⁶

Who issues septic permits in Montana?

Montana DEQ handles covered subdivision sanitation review, while the local health department issues the drainfield permit.³ A Certificate of Subdivision Approval, commonly called a COSA, does not replace the drainfield permit needed to install a drainfield.¹⁰ The county authority pattern lists 47 counties with county-issued septic permits, 7 served by a health district and 2 with state-agency permitting.¹⁷ Because that pattern differs from DEQ's general description, confirm the actual drainfield office on the county page before applying.¹⁷³

DEQ's Subdivision Program reviews land divisions comprising less than 20 acres, plus condominiums and recreational camping vehicle and mobile home parks regardless of parcel size.¹⁸ For a land purchase, request the existing COSA and ask the local health department whether the planned dwelling needs a new or changed drainfield permit.¹⁰ DEQ's on-call engineer is the state contact for subdivision-review questions.¹⁸

Can you live in an RV or tiny home on your land in Montana?

Montana RV occupancy has county-level answers in 12 counties: 4 allow it as a county land-use matter and 8 impose conditions; the remaining 44 are unanswered, not automatically allowed or prohibited.⁴ The allowed group is Fergus County, Musselshell County, Carter County, Petroleum County, with septic, floodplain and other applicable requirements still separate.⁴ Compare the Montana RV-living county list before choosing a parcel.⁴

Tiny-home occupancy has answers in 14 counties: 10 allowed as a county land-use matter, 4 limited and 42 unanswered.⁵ The highest-scoring allowed entries include Judith Basin County, Pondera County, Teton County, Fergus County, Musselshell County.⁵ The Montana tiny-home list links the county-specific conditions.⁵ Some limited RV answers concern rental spaces or RV parks, so ask the county planning office specifically about a personal RV on a private parcel.⁴ DNRC's state-trust-land camping rule applies to recreation on state trust land and does not answer private-land residency.¹⁹

Where are the best Montana counties for a bolthole?

Lake County leads the Montana Index at 79, with limited residential building-permit requirements, zoning and county septic permitting; Gallatin County follows at 77 with the same authority pattern.²⁰ Lewis and Clark County also scores 77, with no residential building permit, zoning and county septic permitting.²⁰ Broadwater County and Mineral County each score 75, with no residential building permit or countywide zoning and county septic permitting.²⁰

The next counties by score are Lincoln County at 74, with no residential building permit and zoning; Sanders County at 74, with limited residential building permits and no countywide zoning; and Meagher County at 73, with no residential building permit and zoning unconfirmed; all have county septic permitting.²⁰ Montana's median county farmland value is $1,283 per acre, a farmland benchmark rather than a specific homesite price.²¹ The median county effective property-tax rate is 0.7%, and the median county property-tax bill is $1,719 annually.²²

What water-right and well rules apply to Montana land?

Montana follows prior appropriation, and 17 counties contain a special groundwater-management regime.²³ A new groundwater use of no more than 35 gallons per minute and 10 acre-feet annually may qualify for a permit exception, but eligibility is not automatic.¹² Combined appropriations from the same source exceeding 10 acre-feet require a permitted water right regardless of flow rate; multi-phase subdivision lots share the combined limit to qualify for the exception.¹²

Beginning January 1, 2026, a buyer developing exempt-well water use must file a Notice of Intent with DNRC before using the water; the filing fee is $400.¹² DNRC reviews a correct and complete submission within 10 business days, and an authorization gives the applicant 5 years to complete the project, put water to use and file a Notice of Completion.¹² Ask the DNRC Water Resources Regional Office for help and check the Water Rights Query System for parcel-specific Notices of Intent before buying.²⁴

Watch-outs

• County building-permit counts apply to unincorporated land; certified city building-code programs can have different requirements inside city limits.¹²⁵
• Montana's Building Codes Program announces updated codes effective September 26, 2026; confirm the applicable edition with the building-code office for a new project.²⁶
• No residential building permit does not waive a drainfield permit or a development permit in a designated Special Flood Hazard Area; ask the local health department and local floodplain administrator.¹⁰¹⁶
• New or modified approaches onto Montana state highways require an approach permit or right-of-way agreement; a changed use can require a new approach permit through the appropriate MDT District Office.²⁷
• We could not confirm a statewide private-land tiny-home occupancy entitlement; ask the county planning office about the parcel and proposed dwelling.⁵

Sources

1. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Montana counties that do not require a residential building permit in unincorporated areas
2. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Montana counties with no county-wide zoning
3. Montana: Engineering Infrastructure & Subdivisions, quoted and re-checked
4. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Montana counties' answers on living in an RV on your own land
5. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Montana counties' answers on living in a tiny home on your own land
6. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Montana counties that require a residential building permit only in some cases (for example floodplain or certain structures)
7. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Montana counties that require a residential building permit in unincorporated areas
8. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Montana counties with county zoning
9. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Montana counties with neither a residential building permit nor county-wide zoning
10. Montana: Engineering Infrastructure & Subdivisions, quoted and re-checked
11. Montana: Montana Code Annotated, Title 37, Chapter 45, Construction Contractors, quoted and re-checked
12. Montana: Exempt Well Updates and Information, quoted and re-checked
13. Montana: Building Permits, quoted and re-checked
14. Montana: Building Permits, quoted and re-checked
15. Montana: 76-2-201. County zoning authorized, MCA, quoted and re-checked
16. Montana: Stream Permitting, quoted and re-checked
17. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Who issues septic permits across Montana's counties: a state agency, a multi-county health district, or the county
18. Montana DEQ — Engineering Infrastructure & Subdivisions (deq.mt.gov)
19. Montana: Camping, quoted and re-checked
20. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: The 8 highest-scoring Montana counties on the Bolthole Index (off-grid and homestead land score out of 100), with each one's building-permit, zoning and septic answers
21. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Median farmland value per acre across Montana's counties (USDA census, the middle county's value; USD/acre), with the five least expensive counties
22. Bolthole Index county rulebook, 56 Montana counties, as of October 9, 2026: Median of Montana's county effective property tax rates and median county property tax bills
23. Montana water rights and groundwater management: National Agricultural Law Center and Bolthole Index groundwater review
24. Montana DNRC — Water Resources (dnrc.mt.gov)
25. Montana: 50-60-301. County, city, and town building codes authorized, MCA, quoted and re-checked
26. Montana Department of Labor & Industry — Building Codes Program (bsd.dli.mt.gov)
27. Montana: Approach Manual for Landowners and Developers, quoted and re-checked

Written October 10, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.