How Much Does an ADU Cost in California?
California ADU cost depends more on your lot and your city than on any price list. Here is what drives the number, and how to finance the total.
- We explain every option, not just one product
- Matched with lenders who finance ADUs
- No obligation to take any offer
How California owners budget for an ADU
Start with the type. A garage conversion reuses an existing slab, walls and roof. An attached ADU shares a wall with the house. A detached or prefab unit needs its own foundation and utility runs. A junior ADU sits inside the home, and the owner has to live on site.
Then get a written estimate broken into cost lines. Lenders want that breakdown.
At a glance
- Biggest variables: type, size, site work and utilities
- Fees: set locally, within state limits
- Property tax: reassessed on the new construction only
- Best number: a written builder estimate
What drives ADU cost in California
Two ADUs with the same floor plan can price very differently in California. Lot slope, soil, distance to sewer and power, and backyard access all land in the bill. Fees vary by city and county, although state law limits impact fees on smaller ADUs. Finishes are the part you control the most. Confirm current fees with your city or county.
| Cost line | What moves it |
|---|---|
| Design and plans | Stock or custom plans, and engineering for the lot |
| Permits and fees | Your city or county fee schedule and the size of the unit |
| Site work and foundation | Slope, soil, equipment access and demolition |
| Utility connections | Distance to sewer, water and power, and panel capacity |
| Construction | Size, type and local labor costs |
| Finishes | Kitchen, bath, flooring and window choices |
Typical price range
A written estimate from a builder who has walked your lot is the most reliable number you can get. Ask for it broken down by the lines above so you can match it to a loan.
Lower cost routes and loans
A garage conversion is often the lowest cost type. A prefab can shorten the build. If the total runs past your equity, a construction loan can lend on the finished value.
Garage conversion ADU cost
Often the lowest cost route, and the loans that fit a smaller project.
Prefab ADU financing in California
How to fund factory deposits, site work and the install.
California ADU construction loans
Paid to your builder in draws as the unit passes inspection.
California ADU cost questions
How much does it cost to build a two bedroom ADU in California?
The lot, the city and the finishes matter more than the bedroom count. Get a written estimate from a builder who has walked your property, broken into the cost lines above.
What happens if you build an ADU without a permit in California?
Your city or county can require you to legalize, correct or remove the unit. Lenders generally will not finance unpermitted work, and it can complicate insurance and a sale.
What are the downsides of ADUs?
Cost and time. Site work and fees can surprise you, and renting the unit makes you a landlord.
Talk to a lender who finances ADUs
Once you have a builder estimate, tell us about your project. We will connect you with a lender who finances ADUs in California so you can compare real terms.
Thanks. We have your details and a lender who finances ADUs will be in touch, usually within one business day.