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What an ADU costs in Orange County Honest 2026 pricing for Orange County ADU projects. These ranges are installed cost — design, permit, construction, and standard finishes — based on jobs we've actually closed in this market.
Installed cost ranges
Detached new-build $425–$575/sqft
Garage / interior conversion $250–$370/sqft Why Orange County prices look like this ☐ Master-planned HOA design review pushes architectural / cladding budgets 15–25% higher. ☐ Coastal Zone CDP in Laguna / Newport adds $20–60k in soft costs and timeline. ☐ Alquist-Priolo geotech (Newport-Inglewood) commonly $12–30k. ☐ Irvine / Anaheim labor cost runs at LA County median. How to read these numbers These are total installed $/sqft, not just construction. The detached range assumes a clean 600–900 sqft new-build with mid-range finishes. Conversions price lower because the shell already exists — most cost lives in plumbing, electrical, and the kitchen. Move outside these ranges and we'll tell you why before you sign anything.
Reference
Terms and guides for this page Glossary terms Coastal Development Permit (CDP) Permit required for construction inside California's Coastal Zone, issued by the city or the California Coastal Commission.
Soils Report Engineering study of subsurface soil conditions, required for hillside and certain ADU lots.
Ministerial Review Permit review based purely on objective standards — no public hearing, no discretion.
Setback Minimum distance a structure must be from a property line.
Construction Loan Short-term loan covering construction costs, converted to a permanent mortgage at completion.
HELOC (Home Equity Line of Credit) Revolving credit line secured by your home's equity — common ADU financing path.
Field guides The Los Angeles ADU permit process, step by step Permitting an ADU inside the City of Los Angeles takes about 8–11 weeks of plan check (LADBS) plus 2–4 weeks of pre-submittal prep. State law caps ministerial review at 60 days from a complete submittal. Total city + utility fees for a 700 sqft detached ADU typically run $13,000–$26,000.
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