Residential Guide
ADU Cost & Permits in Kern County
Real build costs from our current pricing, the state rules that override local pushback, and the permit path from feasibility to certificate of occupancy in Bakersfield and unincorporated Kern County.
The Short Version
What an ADU costs here
Most homeowners start with a number they read online, usually somewhere near $150 a square foot. That figure is almost always a shell price. A permitted ADU is a complete dwelling: foundation, framing, roof, a kitchen, a bathroom, HVAC, its own electrical, and a trench back to the house.
The table below is built from our actual per square foot costs, with general contractor markup and contingency already included. It is the same math behind our instant estimator, not a national average.
Cost Table
Kern County ADU cost by type
| ADU type | Typical size | All-in range | Per sq ft |
|---|---|---|---|
| Garage conversion | 400 sq ft | $135,000 – $215,000 | $336 – $538 |
| Attached ADU | 500 sq ft | $200,000 – $316,000 | $403 – $632 |
| Detached, 1 bedroom | 600 sq ft | $282,000 – $444,000 | $470 – $739 |
| Detached, 2 bedroom | 800 sq ft | $366,000 – $581,000 | $457 – $726 |
Ranges span builder-grade to high-end finishes and include contractor markup and contingency. They exclude permit and utility connection fees, which are paid to the jurisdiction. Every project is confirmed with a site visit before a contract number is issued.
Cost Drivers
Six things that move the number
Utility distance
Every foot of trench between the main house and a detached unit adds cost. Sewer depth and panel capacity are the two items that surprise people most.
Panel & service upgrade
Older Bakersfield homes on a 100-amp service usually need an upgrade before a second kitchen and HVAC system can be added.
Site access & grading
Backyard builds with no gate wide enough for a concrete truck or excavator get handled by smaller equipment, which takes longer.
Finish level
The same 600 sq ft footprint swings well over $100,000 between builder-grade and custom millwork with premium appliances.
Fire sprinklers
If the main house has sprinklers, the ADU generally needs them too. If it does not, state law says the ADU does not trigger them.
Soils & foundation
Expansive soil or a sloped pad means engineered footings, which shows up in the concrete line before anything is framed.
Permits
The permit path, step by step
Feasibility
Confirm lot zoning, setbacks, easements, and where utilities actually run. This is the step that decides whether a detached unit pencils.
Design & Title 24
Plans, structural engineering, and a Title 24 energy compliance report. Kern's climate zone drives insulation, glazing, and HVAC sizing.
Plan check
Submit to the City of Bakersfield or Kern County Building Inspection, depending on whether the parcel is inside city limits. Expect at least one correction cycle.
Fees & issuance
Building permit, plan check, school, and utility connection fees are paid at issuance. State law waives impact fees on ADUs under 750 sq ft.
Build & inspections
Foundation, framing, rough MEP, insulation, drywall, and final. Five to nine months from ground to certificate of occupancy.
Fee schedules change and are set by the jurisdiction, not by us. Confirm current amounts with the Kern County Planning & Natural Resources Department or the City of Bakersfield Building Division before you budget. We pull and manage the permits either way.
State Law
What California guarantees you
California ADU law preempts local ordinances, so a Kern County or Bakersfield rule cannot take these away. The details are laid out in the state's HCD ADU handbook.
- An ADU up to 800 sq ft, 16 feet tall, with 4-foot side and rear setbacks cannot be denied on a lot with an existing or proposed single-family home.
- A complete ADU application must be approved or denied ministerially within 60 days. No public hearing, no discretionary review.
- Impact fees cannot be charged on an ADU under 750 sq ft. Above that, they must be proportional to the primary dwelling.
- Owner occupancy of the main house is not required for ADUs permitted under current state law.
- Off-street parking cannot be required when the ADU is within a half mile walking distance of public transit.
- A garage conversion cannot be forced to replace the parking spaces it removes.
This is general information, not legal advice. Rules are amended most legislative sessions, so verify current requirements for your parcel.
Thinking about an ADU in Kern County?
Run the estimator for a real range, then we'll walk the lot and confirm it.