Straight answers
Are granny pods legal in the US?
There is no national yes or no, because nothing is decided nationally. A granny pod is an accessory dwelling unit, and ADUs are governed by state law where it exists and by city and county zoning everywhere else, so the answer changes between two counties in the same state. The dependable permanent-dwelling route is a modular home carrying your state's program insignia, inspected in the factory to the code the state adopted. A unit on wheels is a different legal object: it places under RV and pad rules rather than as a permanent dwelling, which is the part that surprises families buying for a parent.
Figures verified against the sources below · September 9, 2026
01 — The longer answer
How US zoning, code and classification decide the answer
Three questions decide it, in this order
Does zoning permit a second dwelling on the parcel, what does the local building department require for it, and how will the finished home be classified for title, insurance and financing. The third is the one that gets skipped, and it is the one that determines whether you end up owning a house or a vehicle.
Several states now require your city to allow one
Where a state has passed accessory dwelling unit legislation, the answer is usually more permissive than the neighbourhood assumes. Washington's HB 1337 requires jurisdictions planning under the Growth Management Act to allow up to two accessory dwelling units per single-family lot inside urban growth areas, and prohibits owner-occupancy requirements. New Hampshire has allowed one unit, attached or detached, as a matter of right since 1 July 2025, and municipalities cannot restrict it below 750 square feet. Montana requires municipalities to allow at least one. California requires local agencies to permit them ministerially.
A state ADU mandate does not legalize a home on wheels
This is the trap in the category, and Montana's statute states it plainly: the ADU law does not by itself legalize permanent occupancy of a tiny house on wheels or an RV. The mandate obliges your city to permit a dwelling, and a unit titled as a travel trailer is not one. If the plan is a parent living there year-round, the foundation route is the one that survives contact with the building department.
Who lives there is rarely the restriction
Most ADU rules describe the dwelling, not who sleeps in it, and several states have gone further by banning owner-occupancy conditions outright. The unit that houses a parent this decade is the unit that houses a tenant or an adult child the next, so design it as a home rather than as a temporary arrangement.
We publish a guide for every state we cover with the building code in force and the sources it was checked against, and the comparison table draws the distinction most code guides skip: whether the state's code reaches your build on its own, or whether that is a local decision.
03 — Sources
Each figure above links to the authority it came from.
Washington 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 Department of Housing and Community Development Accessory Dwelling Unit Handbook: local agencies must permit accessory dwelling units ministerially
hcd.ca.gov
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