Orange County ADU Design, Permits & Construction Management
Casita manages your project from feasibility and design through permitting, competitive builder bidding, and construction. We bring The Casita Way — Design. Bid. Build. — to Orange County homeowners, from the coast to the foothills, with one point of contact throughout.
- 01Design
- 02Permit
- 03Bid
- 04Build
ADU construction management in Orange County
Casita is a construction management agency, not a general contractor. We manage the whole project on your behalf; licensed Orange County builders you select through competitive bidding perform the work.
Feasibility
Zoning, lot coverage, setbacks, utilities, HOA rules, and Coastal Zone or fire-zone overlays — we tell you what your Orange County lot can carry before you spend on design.
Design
Custom architectural design and engineering sized to your lot and budget, or an adaptation of a pre-approved plan where your city offers one.
Permitting
Complete permit package, submittal to your city (or the County for unincorporated areas), plan-check responses, and HOA or coastal review run in parallel.
Competitive Bidding
Qualified, licensed Orange County builders price the same permit-ready plans. We compare proposals with you line by line and coordinate the selection of your construction team.
Construction Management
We manage your selected builder through construction — schedule, budget, inspections, and quality — to final inspection and keys.
Every city in Orange County
We manage ADU, garage conversion, and JADU projects in all 34 Orange County cities and in unincorporated communities permitted through the County of Orange.
- Anaheim, CA
- Santa Ana, CA
- Irvine, CA
- Huntington Beach, CA
- Garden Grove, CA
- Orange, CA
- Fullerton, CA
- Costa Mesa, CA
- Mission Viejo, CA
- Westminster, CA
- Newport Beach, CA
- Buena Park, CA
- Lake Forest, CA
- Tustin, CA
- Yorba Linda, CA
- San Clemente, CA
- Laguna Niguel, CA
- La Habra, CA
- Fountain Valley, CA
- Placentia, CA
- Rancho Santa Margarita, CA
- Aliso Viejo, CA
- Cypress, CA
- Brea, CA
- Stanton, CA
- San Juan Capistrano, CA
- Dana Point, CA
- Laguna Hills, CA
- Seal Beach, CA
- Laguna Beach, CA
- La Palma, CA
- Los Alamitos, CA
- Laguna Woods, CA
- Villa Park, CA
- Unincorporated Orange County
Permitting an ADU in Orange County
California ADU law applies everywhere, but Orange County adds a few wrinkles of its own. These are the ones that most often change a project's path.
34 cities, 34 rulebooks
Every Orange County city runs its own planning and building department with its own ADU ordinance, fee schedule, and submittal process; unincorporated areas go through the County of Orange. State law sets the floor — cities must act on a complete ADU application within 60 days (Gov. Code § 66317) and must allow at least an 800 sq ft unit — but the details are local, and we do the homework for your city.
Coastal Zone review
Parts of Seal Beach, Huntington Beach, Newport Beach, Laguna Beach, Dana Point, and San Clemente sit in the California Coastal Zone. State ADU law does not override the Coastal Act, so these parcels may need a Coastal Development Permit or a coastal review on top of the building permit. We confirm your status during feasibility and plan the path from day one.
HOA communities
A large share of Orange County housing is HOA-governed, especially in Irvine, Mission Viejo, Aliso Viejo, Rancho Santa Margarita, Laguna Niguel, and Yorba Linda. HOAs can require architectural review but cannot effectively prohibit an ADU (Civil Code § 4751). We prepare the HOA submittal alongside the city permit so neither one waits on the other.
Fire hazard zones
Foothill and canyon communities — parts of Yorba Linda, Anaheim Hills, Orange, Laguna Beach, and south-county canyons — fall in Very High Fire Hazard Severity Zones, which require ignition-resistant construction (California Building Code Chapter 7A). That shapes materials and cost, so we flag it before design, not after.
A growing number of Orange County cities publish pre-approved ADU plan programs. Where your city has one and it fits your lot, we'll tell you — it can shorten design and plan check.
What we check before you spend a dollar on design
A free consultation answers the questions that decide whether an Orange County ADU pencils — and how big it can be.
- Lot size, zoning, and whether the property already has an ADU or JADU
- Setbacks (4 ft side and rear for new detached units statewide) and lot coverage
- Maximum unit size — cities must allow at least 800 sq ft; detached ADUs up to 1,200 sq ft
- Utility capacity: sewer or septic, water, gas, and electrical panel
- Access for construction equipment and where the unit can realistically sit
- Overlays: Coastal Zone, fire hazard severity zone, hillside, and historic districts
- HOA covenants and architectural review requirements
- Impact fees — waived statewide for ADUs under 750 sq ft; proportional above that
Typical Orange County timeline
- Design
- 4–8 weeks
- City permitting
- 2–4 months
- Competitive bidding
- 3–4 weeks (overlaps plan check)
- Construction
- 4–6 months
Most detached and attached ADUs complete in 9–13 months; garage conversions in 6–10 months. Coastal Zone or HOA review can add time, which we plan for up front.
Orange County pricing
Our online cost estimator is calibrated for San Diego County. Orange County costs and fees vary city by city, so we give you a market-specific budget range at your consultation — and real numbers once licensed builders bid on your permit-ready plans.
Building an ADU in Orange County
Straight answers to the questions Orange County homeowners ask before building an accessory dwelling unit.
Yes. Casita manages ADU projects across all 34 Orange County cities and the unincorporated county — from Anaheim, Santa Ana, and Irvine to Huntington Beach, Newport Beach, Mission Viejo, and San Clemente. We are a construction management agency, not a general contractor: we handle feasibility, design, and city permitting, obtain competitive proposals from qualified licensed Orange County builders, help you compare them, and then manage construction on your behalf through final inspection.
Plan on 9–13 months from first design meeting to move-in for a detached or attached ADU, and 6–10 months for a garage conversion. Design takes 4–8 weeks and construction 4–6 months; city permitting is typically 2–4 months, since California requires cities to act on complete ADU applications within 60 days (Gov. Code § 66317). Properties in the Coastal Zone or in HOA communities can add review time, which we build into your schedule up front.
If your home is in an HOA, you will usually need to submit to its architectural review committee, but the HOA cannot stop you from building. California Civil Code § 4751 makes any HOA rule that effectively prohibits or unreasonably restricts an ADU or JADU on a single-family lot void and unenforceable. Because so many Orange County neighborhoods are HOA-governed, we handle the HOA submittal alongside the city permit so the two approvals run in parallel.
Yes, but expect an extra layer of review. State ADU law does not override the California Coastal Act, so properties in the Coastal Zone in cities like Seal Beach, Huntington Beach, Newport Beach, Laguna Beach, Dana Point, and San Clemente may need a Coastal Development Permit or a coastal review in addition to the building permit. We confirm whether your parcel is in the Coastal Zone during feasibility and plan the permitting path accordingly.
Orange County ADU costs vary by city, site, and unit size, and Casita does not quote a number on a web page. Our free online cost estimator is calibrated for San Diego County construction costs and permit fees, so for an Orange County project we give you a market-specific budget range at a free consultation, then real proposals from licensed builders once your plans are permit-ready. Statewide, California waives development impact fees for ADUs under 750 sq ft.
A licensed general contractor that you select through competitive bidding — Casita is not one of the bidders. Once your plans are complete, we prepare the bid package, obtain proposals from qualified, licensed Orange County builders, compare them with you line by line, and coordinate selection and contracting. During construction we manage the builder for you: schedule, budget, inspections, and quality, through final inspection and keys.
Start Your Orange County ADU
Book a free consultation. We'll review your property, your city's rules, and what Design. Bid. Build. looks like for your project.