01
Feasibility check
We review your parcel, zoning, setbacks, and lot size. You receive a fixed-fee feasibility memo within two weeks.
How much does
an ADU cost?
Get an instant, itemized estimate for your ADU project in Southern California. Adjust size, type, and finishes — pricing updates live.
Select your ADU type below — pricing updates instantly.
Detached
Attached
Conversion
Two Story
600 sqft
320 sqft1200 sqft
Total Estimated Cost
$164,588
Base construction$150,000
Design fee$6,750
Lot slope adjustment$0
Finish quality adjustment$7,838
Estimates are for budgeting purposes only and are not a formal quote. Actual costs vary by site conditions, permitting, and material selections. Contact us for an accurate project estimate.
Pricing breakdown
How ADU costs are calculated
ADU pricing in Southern California is driven by four variables: construction cost per square foot, design and engineering fees, lot conditions, and finish level.
Construction cost per sq ft ranges from $220 for garage conversions and attached ADUs up to $255 for two-story builds. Smaller detached ADUs (under 600 sqft) carry a slightly higher per-foot rate due to fixed costs spread across less area.
Design and engineering fees run $6,750 for units up to 600 sqft and $9,700 for larger units — covering architectural drawings, structural engineering, and Title 24 energy compliance documentation.
Finish quality applies a multiplier to the full project cost: standard finishes add 5% and premium finishes add 12% over the baseline.
Cost factors
What impacts your ADU price
ADU type
Ground-up construction costs more than a garage conversion. Two-story units add structural complexity and a second foundation loading path.
Size
Larger units spread fixed costs across more square footage — but very large ADUs (800+ sqft) require more materials and longer build schedules.
Lot slope
Hillside lots require retaining walls, deeper foundations, and additional grading — adding $12,000–$27,000 to the base cost.
Utility hookups
New gas, electrical, and sewer connections vary by distance to the main house. Most LA County lots are within typical range; rural parcels can add cost.
Permitting
LA City, LA County, and incorporated cities each have different fee schedules. Our pricing assumes standard residential permits; ADUs with fire sprinklers or special conditions may cost more.
Site access
Narrow lots or rear-yard ADUs with limited crane access increase labor time and can affect concrete truck access for foundation pours.
Getting started
How to start your ADU project
02
Design phase
Architectural drawings tailored to your lot — or a Nexor pre-approved plan set if you want to move fast.
03
Permitting
We file with the local building department and manage plan check. Typical LA County turn is 8–14 weeks.
04
Construction
Foundation to framing to finishes in 14–18 weeks. Weekly site reports and a dedicated project manager.
05
Final inspection
We shepherd the final inspection, walk you through the unit, and hand you keys with a full closing binder.
Ready to get an accurate quote?
The calculator gives you a ballpark. A 30-minute call with our team gives you a real number for your specific lot.
Book a free consultation