Lake McDonald and the mountains beyond it under a cloudy sky in Glacier National Park, Montana.

Tiny Homes in Montana: Laws, Rules and Communities

Updated November 4, 2026. Some laws may have changed since then. Confirm with your city or county before you buy land or a home.

The short answer

Yes, you can live in a tiny home full time in Montana, on a permanent foundation and where your city or county zoning allows a house. Montana's state building code does not apply to homes with fewer than five units unless your county, city or town adopts it, so whether anyone reviews your plans depends on where you build. On wheels, no Montana law we found defines a tiny home on wheels, and local zoning decides where you can live in one. Cities and towns with zoning have had to allow at least one ADU by right on a lot with a single-family home since January 1, 2024, and a 2025 law extended that to counties that have zoning. Montana has the 15th highest cost of living of the 50 states, an income tax of 4.7 to 5.65 percent, an effective property tax rate of 0.61 percent (16th lowest), and homeowners insurance averaging $3,765 a year.

On this page. Quick facts, the rules in plain words, where to start, living in Montana, communities and common questions.

In Montana, zoning is local, and so is most building code review for houses. A tiny home on a permanent foundation, anchored to a base built into the ground, is a house. A tiny home on wheels, built on a trailer so it can be towed, has no category of its own in the Montana laws we read, so how one is treated once you live in it depends on your county and, for taxes, on the state's mobile home definition.

This guide covers the state building code and where it applies, the tiny house appendix, tiny dwelling unit zoning, homes on wheels, manufactured and factory-built homes, the 2023 and 2025 ADU laws, septic and wells, and what we found when we looked for communities.

Quick facts

On a foundation (anchored to a base in the ground): a house. The state building code uses the 2024 International Residential Code since September 26, 2026, but it does not apply to homes with fewer than five units unless your county, city or town adopts it.
Tiny house appendix: the state applies it to factory-built tiny houses of 400 square feet or less, not counting lofts. A city, county or town with its own certified building code program decides for itself.
Energy code: the state's energy rules still apply to homes. Where no local building code program covers a small home, they are enforced through the state's builder self-certification program.
On wheels (built on a trailer): no Montana law we found defines one. Local zoning decides where you can live in one, and the state's property tax law counts any trailer up to 8 feet in width or 45 feet in length used as a principal residence as a mobile home.
ADUs (a second, smaller home on the same lot as a house): cities and towns with zoning must allow at least one by right on a lot with a single-family home, and so must counties that have zoning.
Septic (an underground system that treats wastewater where there is no city sewer): a permit from your local health department comes first. Lewis and Clark County, for example, requires one before any construction on the parcel.

Can you live in a tiny home full time in Montana?

Yes, on a permanent foundation where local zoning allows a house. On wheels, it depends on your city or county.

On a foundation, a tiny home is a house. It needs sewer or a permitted septic system, and it has to meet the building code if your county, city or town enforces one. The state's energy rules apply either way.
On wheels, we found no Montana law that allows or bans living full time in one. Your county or city zoning decides.
The state sets no minimum house size that we found. A city or county can create zoning districts for "tiny dwelling units" of 350 to 750 square feet, so ask whether yours has one.

The rules in plain words

Building code

Montana's Department of Labor and Industry adopts the state building code. Since September 26, 2026, the state code for houses is the International Residential Code, 2024 edition, with Montana's changes, under ARM 24.301.154.

For most houses, the state code applies only where a local government chooses it. Under MCA 50-60-102, the state building code does not apply to residential buildings with fewer than five dwelling units, farm or ranch buildings, or private garages and storage buildings for the owner's own use, unless the county, city or town makes it apply by ordinance or resolution. The state cannot enforce the code on those buildings itself.

The state's energy conservation rules are the exception. They apply to homes, and for buildings of fewer than five units that are not otherwise under the state code, they are enforced through the builder self-certification program in MCA 50-60-802.

Cities with their own building code programs set their own effective dates for the new code. Bozeman, for example, applies the 2024 codes to applications submitted on and after January 1, 2027, and Helena reviews permit applications received on or after October 26, 2026 under the 2024 codes.

The tiny house appendix

The national residential code has an appendix with rules for tiny houses, often called Appendix Q. In the 2024 edition it is Appendix BB, Tiny Houses.

Montana's rule adopts Appendix BB. A certified city, county or town building code program may adopt it too.
The state applies Appendix BB to factory-built buildings that meet its definition of a tiny house, 400 square feet or less in floor area not counting lofts, intended for a permanent foundation and used as a single-family home.
Under the same rule, appendices do not apply in a certified local program unless the state authorizes them and the local program adopts them.
Bozeman's building division lists the tiny house appendix as adopted under the 2021 code it enforces until it moves to the 2024 codes on January 1, 2027.

What it means for you is that a factory-built tiny house sold in Montana is reviewed by the state under the tiny house rules. A tiny house built on site is reviewed under them only where a local code program has adopted them, and where no local program covers houses, the state code does not apply to it at all, apart from the energy rules. Ask your building department, in writing, which code and appendices it uses before you design or buy.

Tiny dwelling unit zoning districts

Montana's zoning laws let a county (MCA 76-2-202) or a city (MCA 76-2-302) create zoning districts that allow tiny dwelling units. The law defines a tiny dwelling unit as a home of 350 to 750 square feet, on a permanent foundation, used as a single-family dwelling for at least 45 days or longer.

How the building rules for those units work is not settled. The same sections say "Appendix Q, tiny houses, of the International Building Code as it was printed on January 1, 2023, may govern all other requirements" of a tiny dwelling unit. The tiny house appendix is published in the International Residential Code, not the International Building Code, and in the 2021 edition it was lettered AQ. The state building code rule, meanwhile, applies the tiny house appendix only to factory-built homes of 400 square feet or less. We found no state guidance that reconciles the two. If your city or county has a tiny dwelling unit district, ask its planning and building offices which size limit and which code edition they apply.

Tiny homes on wheels

No Montana law or rule we found defines a tiny home on wheels or says where one can be lived in. Local zoning decides.

For property tax, MCA 15-1-101 defines a mobile home to include "any trailer, housetrailer, or trailer coach up to 8 feet in width or 45 feet in length used as a principal residence." The Department of Revenue can treat a mobile home as part of the real property only once it is attached to a foundation that cannot feasibly be relocated and its wheels are removed.
How that tax definition applies to a tiny home on wheels is not settled. On its face it reaches a trailer-sized home used as a principal residence, but we found no Department of Revenue guidance on tiny homes on wheels. What it means for you is that one you live in may be taxed like a mobile home, so ask your county assessor before you buy.
Montana's zoning protections for manufactured housing do not cover a mobile home or housetrailer as defined in that tax law.
The ADU laws do not mention homes on wheels. They define an ADU as a self-contained unit that complies with or is exempt from the building code, fire code and public health rules.

That is a local zoning question everywhere in the state, so call your county or city before you buy a home on wheels to live in.

Modular and manufactured homes

Modular homes and other factory-built buildings must meet the state codes listed in ARM 24.301.1201. Under ARM 24.301.1241, units manufactured, delivered or sold in Montana must carry a state insignia of approval.

Montana zoning cannot treat manufactured housing or factory-built housing differently from any other homes, in counties (MCA 76-2-202) or cities (MCA 76-2-302). A 2025 law, SB 252, amended both sections to require that zoning treat manufactured and factory-built housing the same as other homes.

In a permit or variance request to place one in a residential zone, the law presumes it will not hurt the value of nearby conventional homes. That presumption can be rebutted.
Manufactured housing here means a home built to the federal HUD code, not a mobile home or housetrailer as the state's tax law defines them.
Factory-built housing means a home assembled in a factory, not made to be readily moved, designed for a permanent foundation, not HUD certified, and meeting the state's factory-built inspection rules.
These sections do not limit historic district conditions, local design review standards or existing covenants.

The ADU laws

Montana has two ADU laws, one for cities and one for counties. Both require at least one ADU by right on a lot or parcel with a single-family home, attached, detached or inside the house. By right means approval without a public hearing, a variance or a conditional use permit.

Cities and towns that have zoning (MCA 76-2-345, from SB 528, in effect since January 1, 2024):

A detached or attached ADU can be no larger than 75 percent of the house's gross floor area or 1,000 square feet, whichever is less.
A city cannot require extra parking or fees in place of parking, owner occupancy, matching design, roof pitch or materials, a family or employment relationship between the households, impact fees, or street improvements beyond repairing damage.
Height, setback, lot size and lot coverage rules for the ADU cannot be stricter than for the house.
A city can charge an application fee of up to $250 per ADU, plus its usual building fees, and can require will-serve letters from city water and sewer.

Counties with zoning (MCA 76-2-215, from SB 532, signed May 12, 2025):

The law applies where the county commissioners have adopted zoning regulations.
A county cannot require owner occupancy, matching design, a family or employment relationship, impact fees, or street improvements beyond repairing damage, and its placement rules cannot be stricter than for the house. The county section does not include the city law's size cap or its parking rule.
A county that had not updated its rules by October 1, 2025 must review and permit ADUs under the state law until it does.
The state Department of Environmental Quality must offer a 15-day expedited sanitation review for an ADU added to a parcel with public water and wastewater service that has capacity. That part of the law ends September 30, 2029.

Both laws leave building codes, fire codes and public health rules in place, and both let local governments regulate short-term rentals. In 2024 the Montana Supreme Court reversed a lower court order that had blocked the city ADU law and a companion duplex law, sending the case back for further proceedings. In March 2026, in a second ruling in the same case, the court upheld a lower court ruling that rejected the challengers' equal protection claim against those laws (2026 MT 53). For ideas on building one, see advice for a tiny backyard ADU.

Septic and wells

Where there is no sewer, you need a septic permit before you build. Under MCA 50-2-116, local boards of health set the rules for sewage disposal, so the permit comes from your local health department. Lewis and Clark County, for example, requires a septic permit for any home that needs wastewater disposal and is not on city sewer, and says you must get it before any construction on the parcel, including drilling a well or digging a foundation. Its permits expire one year after they are issued. Ask your county environmental health office or sanitarian about its process before you buy raw land.

For water, MCA 85-2-306 lets you drill a well without a water right permit outside a controlled ground water area if it pumps 35 gallons a minute or less and no more than 10 acre-feet a year, outside a stream depletion zone. Inside a stream depletion zone the limits are 20 gallons a minute and 2 acre-feet a year. Two or more wells drawing from the same source count together, and a combined draw above those yearly limits needs a permit. You file a notice of intent with the Department of Natural Resources and Conservation first, and the department authorizes or denies it. This exception does not apply inside the Flathead Indian Reservation.

Snow and frost

Montana's residential code rule says the building official determines snow loads. Outside certified city, county or town programs, design snow loads are based on the national ASCE 7-22 standard, and the rule sets a minimum design roof snow load of 30 pounds per square foot after allowed reductions, unless a Montana licensed design professional justifies a different figure. Helena, for example, lists a 30 pound minimum snow load and a 42 inch minimum frost depth to the bottom of footings. Ask your building department for the figures where you build, since they affect the foundation and roof of even a small home.

Where to start

Not sure which office covers your land? USA.gov's local government finder points to a directory of Montana's counties and cities, with their websites and contacts.
Call the city zoning office, or the county if the land is outside city limits. Ask whether tiny homes, ADUs and homes on wheels are allowed there, whether there is a tiny dwelling unit district, and get the answer in writing.
Ask whether the city or county has its own building code program. If it does, ask which code edition it enforces and whether it uses the tiny house appendix. If it does not, ask what permits it still requires.
If the land is not on sewer, call the local health department or sanitarian about a septic permit before you buy, and before any work on the parcel.
For a well, check the limits for your area and file the notice of intent with the Department of Natural Resources and Conservation.
For a home on wheels, ask the county assessor how it will be taxed and ask zoning where you can live in it.
Before buying land, check covenants, since private covenants can still limit ADUs and small homes.

Living in Montana

How Montana compares with the other 49 states on the things people weigh before a move. Figures as of November 2026.

Happiness score (WalletHub 2026). 49.51 out of 100, 30th happiest
Cost of living (MERIC, Q2 2026; U.S. average is 100). 106.0, 15th highest
State income tax. 4.7 to 5.65 percent
State sales tax. None
Property tax, effective rate on owner-occupied homes (Tax Foundation, 2024 data). 0.61 percent, 16th lowest
Homeowners insurance, average a year with $400,000 in dwelling coverage (NerdWallet 2026; U.S. average $2,490). $3,765
Health care (U.S. News). 41st
Education (U.S. News). 16th
Average temperature, 1991 to 2020. 42.6 degrees F
Average precipitation, 1991 to 2020. 18.9 inches a year
Sunshine in Billings. 60 percent of possible sunshine, 89 sunny days a year

Montana has no state sales tax, its income tax runs from 4.7 to 5.65 percent, and its effective property tax rate is 0.61 percent. Its cost of living is a little above the national average, 15th highest among the states. Homeowners insurance averages $3,765 a year with $400,000 in dwelling coverage, compared with a U.S. average of $2,490. U.S. News ranks Montana 16th in education and 41st in health care, and WalletHub ranks it 30th happiest.

Rankings mix many factors, and statewide averages hide differences between regions. Mountain valleys, plains and the larger cities differ in land prices, snow, local rules and whether you can get on sewer, so look at the area where you plan to live.

Tiny home communities in Montana

We could not confirm a Montana tiny home community that people can buy or lease into, or an RV park that takes tiny homes or park models for monthly or longer stays, on its own website as of November 2026. The listings we checked were directories, vacation lodging or a plan from years ago that we could not find a current site for. We would rather list none than send you to one that does not exist.

If you find one, check its own website, ask whether you buy or lease the lot, whether year-round living is allowed and which home types it takes, and contact it directly before you plan around it. We will add communities here as we confirm them.

Tours we have filmed in Montana

We do not have a Montana tour to list here yet. When we do, it will be listed here. Our tours from other states are at Tiny Home Tours by State.

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Frequently asked questions

Is it legal to live in a tiny house in Montana?

Yes, on a permanent foundation where local zoning allows a house, with sewer or a permitted septic system. It has to meet the building code if your county, city or town enforces one, and the state's energy rules apply either way. For a tiny home on wheels, local zoning decides.

Can I park a tiny home on wheels on my own land in Montana?

It depends on your county or city. No Montana law we found defines a tiny home on wheels or says where you can live in one, so local zoning decides. The state's property tax law counts any trailer up to 8 feet in width or 45 feet in length used as a principal residence as a mobile home, so ask your county assessor how one would be taxed.

Does Montana use Appendix Q for tiny houses?

Partly. The state building code adopts the tiny house appendix, Appendix BB in the 2024 edition, and the state applies it to factory-built tiny houses of 400 square feet or less, not counting lofts. A city, county or town with its own certified building code program decides for itself whether to adopt it. Bozeman lists the tiny house appendix as adopted under the 2021 code it enforces until January 1, 2027. Ask your building department in writing.

Can I build an ADU in Montana?

Yes, in cities and towns that have zoning and in counties that have zoning. Cities and towns with zoning must allow at least one ADU by right on a lot with a single-family home, up to 75 percent of the house's floor area or 1,000 square feet, whichever is less, with no owner occupancy rule and no extra parking. Counties with zoning must also allow at least one ADU by right, without an owner occupancy rule. Private covenants can still limit them.

Do I need a septic permit for a tiny home in Montana?

Yes, if the land is not on sewer. The permit comes from your local health department, and some counties require it before any work on the parcel. Lewis and Clark County, for example, requires a septic permit before any construction, including drilling a well or digging a foundation.

Sources

This page explains the rules in general terms and is not legal advice. Local rules vary. Confirm with your city or county before you buy land or a home.

Hero photo: Lake McDonald, Glacier National Park, by Karthik Sreenivas on Unsplash.