Plan Your Dream ADU Today with Accurate Cost Estimates
Build smarter, not harder! Use our California ADU Construction Cost Calculator to get precise cost estimates tailored to your property and preferences. Whether you’re planning a guest house, home office, or rental unit, we’ll help you calculate costs and make informed decisions.
Here’s what impacts the total cost of building an ADU in California:
Get a detailed breakdown of costs based on your ADU size, construction type, and finishes.
Calculate costs specific to your location, lot conditions, and preferences.
Plan ahead with clarity and avoid unexpected expenses.
Start your journey now! Get an instant cost estimate, tailored to your unique needs, and take the first step toward creating your perfect ADU.
The size of your ADU is one of the biggest factors in determining cost. Larger ADUs cost more overall but are more affordable per square foot.
ADU Size (sq ft) | Low Estimate | High Estimate |
---|---|---|
300 sq ft | $37,500 | $90,000 |
500 sq ft | $62,500 | $150,000 |
800 sq ft | $100,000 | $240,000 |
1000 sq ft | $125,000 | $300,000 |
1200 sq ft | $150,000 | $360,000 |
The type of ADU project you choose will influence your total cost. Converting existing space is often less expensive than building a new detached unit.
Construction Type | Cost Range (per sq ft) |
---|---|
Conversion (garage, attic, basement) | $125 - $200+ |
Attached ADU | $150 - $250+ |
Detached ADU | $180 - $300+ |
Over Existing Structure | $200 - $350+ |
Building on a sloped lot increases costs due to additional work like grading, retaining walls, and limited access. Expect a 25% higher cost for sloped lots.
The finish level you choose will directly impact costs. Here’s a breakdown:
Finish Level | Description | Average Cost / sq ft |
---|---|---|
Basic | Entry-level fixtures, carpet flooring, vinyl windows. | $10 - $20 |
Standard | High-quality finishes, granite countertops, stainless steel. | $20 - $40 |
Premium | Top-tier finishes, custom woodwork, and ceramic tiles. | $50+ |
These planning and administrative expenses are essential for any ADU project:
Service | Average Price |
---|---|
Design | $2,000 - $30,000+ |
Architectural Plans | $2,000 - $40,000+ |
Engineering | $0 - $5,000+ |
Permits & Application Fees | $1,500 - $8,000+ |
Impact Fees (over 750 sq ft) | $2,000 - $14,000+ |
Utility Fees | $0 - $20,000+ |
Project Management | $0 - $20,000+ |
We recommend setting aside at least 10% of your construction budget for unforeseen costs like material price hikes or supply chain delays.
"Min managed over 30 tenant improvements, build-out of a restaurant, mixed-use apartment building, and all major capital renovation projects starting from contract negotiation to construction management and close-out."
Adam Nathanson President and CEO"UNI Construction helped my company with getting a permit in the City of LA by providing architectural drawings and helping us with questions that the city was asking. Min was very helpful and very quick to respond, he was able to work on the project with short notice for us, which was incredibly helpful with keeping our client happy. He made sure to continue following up with us regarding the status of the permit."
Yasmine P. Preferred One Plumbing, Los Angeles, CA"Super good. Quality super top, nice person. Got great deal for permit drawing. Highly recommended."
Sandy U. Consultant, Walnut, CACalifornia
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