Article

Prefab Cottages and ADUs in California 2026: The Makers

November 13, 2026

Written by

Kai Andrew

If you want a prefab backyard unit in California with installation in the published price, start with Homeplex in Long Beach. Its Casita 550 starts at $214,750 installed for 560 square feet, 1 bedroom, and 1 bathroom, or $383 per square foot. Nestadu delivers fully assembled units in the Bay Area, Sacramento, Los Angeles, and San Diego, from $138,000 for a 200-square-foot Nest, and does not say whether installation, the foundation, or permits are included. kitHAUS builds smaller modules in Southern California from $119,000 with a bathroom and kitchenette, and quotes installation as a share of that price.

Homeplex prices the installed unit. Nestadu and kitHAUS price the unit and leave the rest to a quote. Our prefab ADU guide covers Abodu, Samara, Dvele, Studio Home, and California accessory dwelling unit (ADU) law. This guide covers the other makers that publish California prices, the state program that certifies factory-built homes, and the short-term rental rules in 2 cities.

The California Makers Table

The table ranks each unit by published price divided by published size, lowest first. Each maker’s price covers different work, so read the “What the price includes” column first. For Homeplex, the size is the gross figure the maker lists.

Rank	Model and maker	Price as published	Size	Price per sq ft	Beds and baths	What the price includes, as the maker states it	Where it installs
1	Casita 1250, Homeplex	$336,750 installed, starting	1,260 sq ft	$267	3 bed, 2 bath	Site feasibility, site prep with a standard foundation and utility installation, transportation up to 200 miles, permit management, and installation. City permit fees, third-party reports, and utility or impact fees are excluded	Not published. Office in Long Beach
2	Casita 1050, Homeplex	$316,750 installed, starting	1,050 sq ft	$302	3 bed, 2 bath	Same as the Casita 1250	Not published
3	Casita 805, Homeplex	$276,750 installed, starting	804 sq ft	$344	2 bed, 2 bath	Same as the Casita 1250	Not published
4	Casita 550, Homeplex	$214,750 installed, starting	560 sq ft	$383	1 bed, 1 bath	Same as the Casita 1250	Not published
5	Nest Two, Nestadu	$317,000, starting	638 sq ft	$497	2 bed, 1 bath	Complete interior and exterior finishes, delivered fully assembled. The page does not say whether installation, foundation, permits, or utilities are included	Bay Area, Sacramento, Los Angeles, and San Diego
6	Nest One, Nestadu	$263,000, starting	497 sq ft	$529	1 bed, 1 bath	Same as the Nest Two	Same as the Nest Two
7	Nest, Nestadu	$138,000, starting	200 sq ft	$690	Studio. The bath is optional	Same as the Nest Two	Same as the Nest Two
8	Nest Studio, Nestadu	$270,000, starting	330 sq ft	$818	Studio, 1 bath	Same as the Nest Two	Same as the Nest Two
Not ranked	k5.10 with bath and kitchenette, kitHAUS	From $119,000	11 by 21 ft	Not published	Bath and kitchenette	The module. Delivery is "TBD based on location"	Not published. Built in Southern California
Not ranked	k6.12 with bath and kitchenette, kitHAUS	From $150,000	13 by 25 ft	Not published	Bath and kitchenette	Same as the k5.10	Not published

kitHAUS gives “235 to 330 square feet” for the whole series and no size for each module, so its rows are not ranked. Nestadu’s homepage lists the Nest One at 500 square feet, and its prefab page lists 497. The table uses the prefab page.

What Each Price Leaves Out

Homeplex. Its FAQ lists costs beyond typical site conditions: crane access, a site more than 150 feet from the driveway or street, electrical panel upgrades, demolition or tree removal, retaining walls, required fire sprinklers, and sewer injector pumps. Homeplex says it is the preferred installer of ADU CREW’s prefab ADUs.
Nestadu. The configurator adds finish packages at $15 or $30 per square foot, stucco at $7 per square foot, wood siding at $10 per square foot, and solar at $12,000 for 4 kilowatts or $30,000 for 8 kilowatts with a battery. The lead time is 8 to 10 months. Nestadu says its units are built by “our factory partners” and does not name them. As an example only, the Nest One with the $30 package comes to $277,910 before any site work.
kitHAUS. Its about page says modules are made in its Southern California factory and shipped flat. Its modules page puts installation by the kitHAUS team at about 15% of the module price on a project without a permit and 20% to 24% on a permitted one. As an example only, that is $17,850 on the $119,000 k5.10, or $23,800 to $28,560 if permitted.

If you want a cottage kit that your own crew builds, DC Structures ships pre-cut kits across California at $40.40 to $84.00 per square foot, and says the finished cost can be 3 to 5 times the kit price. Kits that ship to the lower 48 states are compared in our prefab cottages guide.

How California Certifies a Factory-Built Home

Sonoma County’s factory-built housing permit procedure, version 06/23/2025, cites California Health and Safety Code Division 13, Part 6, and Title 25 of the California Code of Regulations. It requires a permanent foundation, and it says that once constructed on site, factory-built housing is a permanent dwelling unit.

County inspectors verify the California Department of Housing and Community Development (HCD) Insignia of Approval on each unit or component. They inspect the parts that are not factory-built, such as foundations, garages, and decks. The county charges no plan check fee for the factory-built components and charges plan check on the on-site construction.

Homeplex’s FAQ says manufactured ADUs are certified by the U.S. Department of Housing and Urban Development (HUD) and modular ADUs by HCD. Its Casita 550 page calls that unit a manufactured detached ADU. Ask each maker in writing whether your unit carries an HCD insignia or a HUD label, because the label decides which rules your county applies.

For pre-approved ADU plans and the rental term in state ADU law, read our prefab ADU guide.

Short-Term Rental Rules in 2 Cities

Each California city sets its own rental rules. These 2 are from each city’s own page.

San Diego. The city’s short-term residential occupancy page says: “The San Diego Municipal Code prohibits using ADUs for short-term rental and will result in a Code violation.” Only companion units permitted before the October 15, 2017, prohibition may be used. Whole-home licenses outside Mission Beach are capped at 1% of the city’s housing units, and a Tier 2 home-sharing host must live on-site.
Sacramento. The city’s ADU resource center says ADUs created under the state ADU standards must be rented for terms longer than 30 days. ADUs and other residential units may be used as a short-term rental for a total of 90 days per calendar year unless the owner obtains a Bed and Breakfast Inn conditional use permit (CUP). Every short-term rental needs a Short-Term Vacation Rental Permit from the Revenue Division.

No maker publishes revenue figures, so the ADU math post shows what a backyard unit earns.

Where to Start

Compare installed prices. Homeplex is the only maker here that publishes one. Its price includes the foundation, utility installation, transportation up to 200 miles, and permit management. Ask Nestadu and kitHAUS for the same items in writing before you compare.

Check the larger Homeplex units. The Casita 1250 adds 700 square feet over the Casita 550 for $122,000, or $174 per added square foot, against $383 per square foot for the Casita 550.

Get Nestadu’s site costs quoted. Nestadu does not say whether installation, the foundation, or permits are included. Its prices run from $497 to $818 per square foot, so get those costs quoted before you use them in a budget.

Read the city’s ADU rental rule before you choose a unit. San Diego prohibits short-term rental in an ADU, and Sacramento allows 90 days a year.

Before You Order

Run these 3 checks before a deposit, in order.

Read the city’s rules. Use the zoning rules guide to find the ADU and short-term rental ordinances for your address. If the city requires terms longer than 30 days, underwrite the unit as a monthly rental.
Price the site work. Run the lot through the site-prep cost estimator. For delivery, permits, and fees, read the cost of prefab homes.
Confirm the loan. Read how to finance an ADU and start with the lender locator. Ask whether the lender finances an HCD modular unit, a HUD manufactured unit, or both.

Finished units from makers outside California are in the 8 best prefab cabins, rated. What works once a backyard unit is in is covered in the Backyard Playbook. For related comparisons, see prefab ADUs and prefab cottages.

Planning a backyard unit in California? Book a free strategy call.

Host Camp is not a licensed tax, legal, or financial adviser. Confirm figures for your situation with a professional.

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