Straight answers
What is a prefab ADU?
A prefab ADU is an accessory dwelling unit built in a factory and installed on your lot, instead of framed stick by stick in your backyard. The dependable permanent route is a modular unit built to the building code your state or province enforces, inspected at the factory stage, and treated by the municipality as a building. The same footprint can also be a park model or a home on wheels, but those place under different rules and are financed as personal property, which is the part that surprises ADU buyers most.
01 — The longer answer
Prefab ADUs, from cost to permission
How much does a prefab ADU cost?
There is no honest single number, because the installed cost is the unit plus delivery, foundation, utility connections, and permits, and the site half of that list is priced by your lot, not by the home. Anyone quoting one figure without seeing your parcel is guessing. KYRAX builds ADU-scale modulars at 10' x 32' and 12' x 44', with launch pricing announced at consultation, and we publish a price transparency index of what other builders actually print so you can see the market before you talk to anyone.
Can I build an ADU on my property?
Zoning decides, parcel by parcel. The direction of travel is with you: Washington requires cities inside urban growth areas to allow up to two accessory dwelling units per single-family lot, New Hampshire has allowed one, attached or detached, as a matter of right since July 2025, Montana requires municipalities to allow at least one, and California permits them ministerially. Our state guides carry the code facts with their sources, and the free lot check reads your municipality against the guides we have verified.
Prefab ADUs for sale: what you are actually buying
A listing price usually buys the unit, not the installed home, so compare what each seller excludes before comparing totals. The other thing to check is the standard the unit is built to, because that decides whether your municipality treats it as a building and whether a lender treats it as real property. KYRAX modulars are built to CSA A277 for Canada and the IBC/IRC modular pathway for US delivery, with certification completed before the home ships.
In Canada the same building goes by different names: a laneway home, garden suite, or secondary suite depending on the city. The rules work the same way, municipality by municipality, and our city guides publish the bylaw figures with sources for six BC and Ontario municipalities.
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