ADU Pricing · 2026
How Much Does an ADU Cost in California? (2026 Prices)
A finished, permitted ADU in California typically runs $180,000 to $560,000 all-in in 2026, depending on size. At Framework First, our 450-square-foot studio is $180,000 and our largest 1,200-square-foot, three-bedroom home is $557,000, and those are total project prices, not a base price you build on top of. A permitting budget, plans, foundation, the factory build, delivery, utility hookups, appliances, and final inspection are all built into that number, with your exact permit costs confirmed for your property in the feasibility study.
That last part matters more than the headline number. The most expensive surprise in ADU building isn’t the home, it’s everything that gets quoted separately and added later.
The short version: A done-for-you ADU in California costs roughly $180K to $560K.
Framework First prices by model (all-inclusive)
| Size | Bed / Bath | All-in price* | Delivery |
|---|---|---|---|
| 450 sq ft | Studio / 1 | $180,000 | 4 months |
| 660 sq ft | 1 / 1 | $287,000 | 5 months |
| 660 sq ft | 2 / 1 | $309,000 | 5 months |
| 945 sq ft | 3 / 2 | $434,000 | 6 months |
| 1,200 sq ft | 3 / 2 | $507,000 to $557,000 | 7 to 9 months |
*Includes a permitting budget, not final permit costs. Permits and property-specific site work (septic, retaining walls, etc.) vary by property and are confirmed in your feasibility study.
See the full model lineup for all 14 configurations, or run the numbers on financing and rental income for any size.
What “all-inclusive” actually covers
When we quote a price, it includes: a permitting budget for the city paperwork and process, the site plan and Title 24 energy compliance, project management, the unit and all finish work, foundation work, appliances and custom cabinets, crane delivery and transportation, the entrance and deck installation, and status updates the whole way. Your exact permit costs are set by your city and confirmed in your feasibility study, and once that’s locked in, your contract price is fixed.
That’s worth comparing line by line against any quote you get, because many ADU quotes leave out permits, foundation, utility hookups, or appliances, each of which can add $15,000 to $50,000.
How prefab compares to site-built
A custom site-built ADU in California commonly takes 16 to 24 months and the all-in cost climbs once permits, foundation, utility hookups, and finish work are added on top of the base build. Building 97% of the home in a climate-controlled factory, in parallel with the foundation work on your property, is how a prefab ADU comes in lower and delivers in as little as 4 months, with no weather delays and no crew on your property for half a year. The advantage isn’t a lower unit cost on paper, it’s that once your feasibility study locks in your property’s permit and site costs, the number on your contract is the number you actually pay.
What drives the price up or down
- Size and bedroom count, the biggest lever.
- Design style, our Classic Craftsman finish is standard; Urban Farmhouse and Ultra Modern are upgrades.
- Site conditions, sloped lots, long crane reach, or sewer/electrical upgrades can add cost. A feasibility study prices these for your specific lot before you commit.
Does the cost pay for itself?
Often, yes. A 660-square-foot ADU rents for roughly $2,500 to $2,900/month in much of the Monterey Bay and Silicon Valley, and an ADU typically adds around 115% of its cost to your property value. The ROI calculator shows financing payment, rental cash flow, and equity gain side by side.
Frequently asked questions
What is the cheapest ADU I can build?
Our most affordable home is the 450 square foot studio at $180,000, which already carries a permitting budget along with foundation, delivery, appliances, and final inspection.
What does “all-inclusive” actually cover?
A permitting budget, plans, the foundation, the factory build, crane delivery, utility hookups, appliances, and final inspection. Exact permit costs are set by your city and county, so they’re confirmed in your feasibility study rather than fixed before we’ve seen your lot, and property-specific site work like a septic upgrade or retaining wall isn’t part of the listed model price, though we can handle it in-house as part of your contract.
Are there hidden costs later?
No. Site-specific conditions like long utility runs or slope are identified in the feasibility study and priced before you commit, not discovered mid-project.
Want a real number for your property, not a range? See if your lot qualifies and we’ll tell you exactly what it would cost to build there.