Abodu
CaliforniaBuilds modular backyard homes and ADUs across California, with state-approved plans and fixed all-in pricing, and says installation can take as little as one day.
Order is editorial. Descriptions come from each company's own website, last checked October 2026. A listing is not an endorsement. How we work.
Villa
Calls itself a leader in offsite construction and offers to handle an ADU, a home build or a development from start to finish.
Samara
Designs and builds homes, backyard ADUs and multifamily housing.
Cover
Southern CaliforniaDesigns, permits and builds custom all-steel homes, ADUs and fire rebuilds in Southern California, installed in weeks.
Dweller
Portland, OregonBuilds ADUs in Portland, Oregon using modular construction and what it calls an innovative ownership structure, aimed at lowering the cost of building and owning.
Studio Home
Prefab ADUs and modern sheds with designer finishes and customizable window and door combinations.
Dvele
High-performance, all-electric prefab homes that the company says exceed Passive House standards.
Hapi Homes
Prefab homes it describes as sustainable and built in 12 weeks.
Method Homes
Architect-designed custom modular homes built with off-site construction.
ideabox
Customizable, energy-efficient prefab homes with flexible floor plans.
Stillwater Dwellings
Luxury prefab and modular homes built with sustainable materials.
Honomobo
Modern prefab and modular homes designed and built in Alberta, delivered across Canada and the United States.
Kanga Room Systems
TexasPrefabricated structures such as guest houses and offices, sold turnkey or as DIY kits, serving Texas and beyond.
kitHAUS
Prefab modules in a range of sizes, from its k3 to its k8 and k9, plus custom work.
BOXABL
Factory-built housing units, including its Casita, under the tagline The Future of Housing.
Den Outdoors
More than 40 cabin and home plans designed to bring the outdoors in. Plans, not a builder.
Mighty Small Homes
Energy-efficient small house kits meant for owners to build themselves.
Wheelhaus
Modular prefab cabins and tiny homes, including models on wheels. Check whether your city treats wheeled units as ADUs.
Clayton Homes
Manufactured, modular and CrossMod home options.
Cavco
Manufactured and modular homes, plus park model RVs.
Skyline Homes
Manufactured, modular and mobile homes and park model RVs, sold through dealers.
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Costs
What an ADU really costs, and where the money goes
The best public numbers we could find, what they include, and why a small unit costs more per square foot than your house did.
4 min read · 3 sources
Costs
Five real ADU projects, broken down line by line
A public housing agency built five ADUs and published every cost. Here is what they paid for permits, surveys, design and construction.
3 min read · 2 sources
Design and build
Prefab vs site-built ADUs
Factory-built units can be faster and sometimes cheaper. The savings depend on your lot, your city and what the quote leaves out.
3 min read · 4 sourcesNewsletter
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