Orange County

    ADU Construction Cost in Orange County (2026): City-by-City Breakdown

    A adu construction in Orange County costs $315–$525 per sq ft, with a typical mid-size ADU running $95k–$189k at the county average. Small projects start around $63k; large or high-end work can reach $473k or more.

    Orange County runs about 5% above the LA County baseline due to coastal demand from Newport to Laguna, master-planned community standards, and concentrated trade labor.

    Get Matched See City-by-City Costs
    OC cost
    $315–$525 per sq ft

    ADU Construction Cost by Size — OC Average

    County-average ranges (1.05× LA County baseline). Individual cities vary — see the table below.

    SizeTypeRangeLowHigh
    SmallJADU / studio150–400 sq ft$63k$137k
    Medium1-bed garage conversion400–600 sq ft$95k$189k
    LargeDetached 2-bed800–1,200 sq ft$263k$473k

    ADU Construction Cost by City in Orange County

    Every city in Orange County, sorted alphabetically. Totals reflect each city's local cost multiplier. Cities in color have full project-specific pages.

    CitySmallMediumLarge
    Aliso Viejo$63k–$137k$95k–$189k$263k–$473k
    Anaheim$58k–$125k$87k–$173k$240k–$432k
    Brea$60k–$130k$90k–$180k$250k–$450k
    Buena Park$57k–$122k$85k–$169k$235k–$423k
    Costa Mesa$65k–$141k$97k–$195k$270k–$486k
    Cypress$58k–$125k$87k–$173k$240k–$432k
    Dana Point$72k–$156k$108k–$216k$300k–$540k
    Fountain Valley$60k–$130k$90k–$180k$250k–$450k
    Fullerton$58k–$126k$88k–$175k$243k–$437k
    Garden Grove$56k–$121k$84k–$168k$233k–$419k
    Huntington Beach$66k–$143k$99k–$198k$275k–$495k
    Irvine$67k–$146k$101k–$202k$280k–$504k
    La Palma$58k–$125k$87k–$173k$240k–$432k
    Laguna Beach$87k–$189k$131k–$261k$363k–$653k
    Laguna Hills$63k–$137k$95k–$189k$263k–$473k
    Laguna Niguel$67k–$146k$101k–$202k$280k–$504k
    Lake Forest$60k–$130k$90k–$180k$250k–$450k
    Los Alamitos$63k–$137k$95k–$189k$263k–$473k
    Mission Viejo$63k–$137k$95k–$189k$263k–$473k
    Newport Beach$90k–$195k$135k–$270k$375k–$675k
    Orange$60k–$130k$90k–$180k$250k–$450k
    Placentia$58k–$126k$88k–$175k$243k–$437k
    Rancho Santa Margarita$63k–$137k$95k–$189k$263k–$473k
    San Clemente$66k–$143k$99k–$198k$275k–$495k
    San Juan Capistrano$66k–$143k$99k–$198k$275k–$495k
    Santa Ana$55k–$119k$82k–$164k$228k–$410k
    Seal Beach$66k–$143k$99k–$198k$275k–$495k
    Stanton$55k–$120k$83k–$166k$230k–$414k
    Tustin$60k–$130k$90k–$180k$250k–$450k
    Villa Park$75k–$163k$113k–$225k$313k–$563k
    Westminster$57k–$124k$86k–$171k$238k–$428k
    Yorba Linda$63k–$137k$95k–$189k$263k–$473k

    Want an exact adu construction price for your home?

    Skip the averages — get up to 3 real bids from licensed OC contractors.

    Get Matched

    What Affects ADU Construction Cost in Orange County?

    • ADU type (JADU vs attached vs detached).
    • Site prep and grading.
    • Utility connections.
    • CA Title 24 energy compliance.
    • City ADU permit timeline.
    • OC market dynamics: coastal demand from Newport to Laguna, master-planned community standards, and concentrated trade labor, which shifts adu construction totals about 5% above the LA County baseline.
    • City variation within OC: coastal and hillside cities can run 15–30% above the county mid-point, while inland labor markets price 10–20% below.

    ADU Construction Sub-Type Comparisons

    Garage Conversion ADU vs Detached ADU

    Garage conversions reuse the existing slab and shell; a detached new-build ADU costs more but unlocks larger floor plans and higher rent.

    Junior ADU (JADU) vs Attached ADU

    A JADU (≤500 sq ft, within the home) shares utilities; an attached ADU is a true second unit with its own entrance and meter.

    How to Get the Best Price on a ADU Construction in Orange County

    1. Get 3 line-itemized bids on the same scope through Keystone Connect — OC adu construction pricing varies 10–25% between contractors.
    2. Compare bids from contractors based in multiple OC cities; inland-based crews servicing coastal jobs often beat coastal-based pricing.
    3. Bid in shoulder seasons (Jan–Mar or Sep–Oct) when OC contractor schedules are open and rush premiums disappear.
    4. Verify CSLB license, insurance, and bond before paying any deposit. California caps deposits at $1,000 or 10% of contract, whichever is less.

    Frequently Asked Questions — ADU Construction in Orange County

    Keep exploring

    Compare adu construction costs across Orange County, or browse other projects and guides.

    Get Matched with Licensed OC Contractors

    Tell us about your adu construction and we'll match you with up to 3 vetted contractors anywhere in Orange County.

    Please provide your details, and we will call you at your preferred time to understand your project scope and guide you through the next steps in getting assigned to the right contractor.

    Privacy Policy·Terms and Conditions