Straight answers
Can you put a tiny house in your backyard in the US?
Often yes, when it is permitted as an accessory dwelling unit, and the dependable route is a unit on a permanent foundation that the local building department treats as a building. Zoning is set by your city or county, but several states now oblige municipalities to allow a backyard home: Washington requires up to two accessory dwelling units per single-family lot inside urban growth areas, New Hampshire allows one, attached or detached, as a matter of right, Montana requires municipalities to allow at least one, and California requires them to be approved ministerially. A tiny house on wheels is a different legal object. It is usually titled like a vehicle, and a state ADU mandate does not by itself make it a place someone can live full time.
Figures verified against the sources below · September 21, 2026
01 — The longer answer
What decides whether a backyard tiny house is allowed
Wheels or foundation decides it before zoning does
The first question is not your lot, it is what the home is. A unit built on a trailer and titled as a travel trailer or recreational vehicle is regulated as a vehicle, and zoning treats a vehicle parked in a backyard differently from a dwelling. Montana's accessory dwelling unit statute says so plainly: it does not by itself legalize permanent occupancy of a tiny house on wheels or an RV. The mandate obliges the city to permit a dwelling, and a vehicle is not one. A factory-built home carrying your state's modular program insignia, or a home built on site under the local residential code, is reviewed as a building, and that is the version accessory dwelling unit laws were written for.
What makes a backyard building a dwelling
California's statute is a useful model because it spells out the test most codes apply in some form. Government Code section 66313 defines an accessory dwelling unit as an attached or detached residential dwelling unit providing complete independent living facilities for one or more persons, with permanent provisions for living, sleeping, eating, cooking and sanitation on the same parcel as the primary home. The definition expressly includes an efficiency unit and a manufactured home. Read the other way, it tells you what a building needs before the law treats it as a home: a kitchen, a bathroom and somewhere to sleep, all permanent.
Backyard guest house or ADU: often the same building
A backyard guest house with a kitchen and a bathroom meets that definition, so it is usually permitted as an accessory dwelling unit whoever ends up staying in it: guests this year, a parent or an adult child next, a tenant later where the rules allow. A building without cooking facilities is typically reviewed under a jurisdiction's accessory structure rules instead, and those rules vary enough that the only reliable answer is your building department's. Decide whether you want a kitchen before you apply, because it changes the category, the inspections and the servicing, not just the floor plan. A modular guest house built to your state's program is reviewed the same way as any other building of its kind.
State laws set a floor, and your city sets the rest
Where a state has an accessory dwelling unit statute, the answer is usually more permissive than neighbours assume. New Hampshire's version bars municipalities from restricting the unit below 750 square feet of living space, Washington's prohibits owner-occupancy requirements, and California's removes discretionary review. None of them settles setbacks, height, utility connections or design standards, which stay local. Our state guides publish the building code in force in each state we cover, with the sources each figure was checked against, and the granny pod laws page sets out what the four clearest statutes actually oblige your city to allow.
What a backyard tiny house for sale actually includes
A listed price usually buys the unit, not the installed home. Delivery, the foundation, water, sewer or septic, electrical service and permits sit on top of it, and your lot sets most of that cost rather than the home. Classification follows the unit into financing as well: a home permanently set on a foundation is real property and takes the mortgage path, while a home on wheels stays personal property and is financed like a vehicle. Ask which standard a unit is built to before comparing prices, because that decides whether the building department and the lender treat it as a house.
If your backyard is in Canada the rules are municipal in the same way, but the categories have different names, garden suite, laneway home or secondary suite depending on the city. The British Columbia version of this question has its own answer, and the free lot check reads the municipalities we have published guides for.
03 — Sources
Each figure above links to the authority it came from.
California Government Code 66313(a), as amended by Stats. 2025, Ch. 520 (SB 543), effective 1 January 2026: an accessory dwelling unit is an attached or detached residential dwelling unit providing complete independent living facilities for one or more persons, with permanent provisions for living, sleeping, eating, cooking and sanitation on the same parcel as the single-family or multifamily dwelling, and includes an efficiency unit and a manufactured home
leginfo.legislature.ca.govWashington HB 1337, RCW 36.70A.680 to .696: cities and counties planning under the Growth Management Act must allow up to two accessory dwelling units per single-family lot inside urban growth areas, with owner-occupancy requirements prohibited
app.leg.wa.govNew Hampshire RSA 674:71 to 674:73 as amended by HB 577, effective 1 July 2025: one accessory dwelling unit, attached or detached, allowed as a matter of right where single-family dwellings are permitted, and municipalities may not restrict the unit below 750 square feet of living space
nhmunicipal.orgMontana SB 528, MCA 76-2-345, effective 1 January 2024: municipalities must allow at least one accessory dwelling unit on single-family lots
archive.legmt.govCalifornia HCD Accessory Dwelling Unit Handbook: local agencies must permit accessory dwelling units ministerially
hcd.ca.gov
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