ADU Design-Build

ADU Design-Build Contractor in Orange County

Architecture, engineering, permits and construction under one contract, one accountable team from first sketch to final inspection.

How does a homeowner check an ADU design-build contractor in Orange County?

Look up the license on the CSLB website, confirm that design, permits and construction are in one written contract, and ask for an itemized price before you sign. L Square holds CSLB #1095476 and runs design through final inspection under one contract. Call (949) 374-7980.

Updated September 24, 2026

Get your free quote→ (949) 374-7980

California fixes the clock on an ADU application: under Gov. Code 66317 a complete application is approved ministerially, with no hearing and no discretionary review, and the city has 60 days to approve or deny it. Design-build matters because one contract owns everything that clock depends on: the drawings, the structural engineering, the Title-24 package and the plan-check responses. When those sit with separate firms, every correction has to travel between them before anyone can answer it, and that waiting is time you pay for.

How long does ADU approval take, and what does design-build change?

The short answer

Sixty days, by statute. Gov. Code 66317(a)(3) gives a permitting agency 60 days to approve or deny a complete ADU application once there is an existing dwelling on the lot, and if it does not, the application is deemed approved. The approval itself is ministerial under 66317(a)(1): no hearing, no discretionary review. What design-build changes is not the deadline but who answers plan check. Under one contract a correction is answered by the same people who drew it, rather than forwarded between an architect and a builder who each wait on the other.

What state law fixes	Section	The number
Approval is ministerial, no hearing, no discretionary review	Gov. Code 66317(a)(1)	By right
Decision deadline once the application is complete	Gov. Code 66317(a)(3)	60 days
If the agency misses that deadline	Gov. Code 66317(a)(3)	Deemed approved
Parking the ADU itself must provide	Gov. Code 66314(d)(10)(A)	One space at most
Replacing parking lost when a garage converts	Gov. Code 66314(d)(11)	Cannot be required

Read the full Orange County permit path →

Real project examples

Real ADU build examples from the Orange County & Los Angeles area

Browse L Square ADU work across multiple completed examples, including exterior details, interiors and finish inspiration.

View real ADU construction examples

Real ADU build example by L Square Design and Build

Completed ADU example from L Square project work

Finished ADU project example from L Square Design and Build

Why design-build beats design-bid-build

With one contract you get a single point of accountability. There’s no handoff between a separate architect and builder, the design is drawn to be buildable on budget, and the schedule is fixed up front. Homeowners comparing a garage conversion ADU and a custom ADU can evaluate both paths before committing to plans.

Our process

Five clear stages (consultation, design, permitting, construction and handover) with weekly updates so you always know where your project stands.

What’s included

Architectural drawings, structural engineering, Title-24 energy compliance, the full city submittal, and construction by our own crews, packaged in one contract. Review the California ADU cost guide and Orange County permit guide before requesting a scope.

Design-build across the different ADU types

The contract structure matters more on some projects than others. A garage conversion hides most of its risk inside an existing structure, so having the designer and builder on the same side of the table is what keeps discoveries from becoming change orders. A detached build front-loads its risk into siting and utilities instead. A junior ADU is small enough that the coordination overhead is the main cost. Same contract, different places where it earns its keep.

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Why build with L Square

Design, permits and construction under one roof. L Square is a licensed Orange County design-build team (CSLB #1095476). One contract covers architecture, engineering, city approvals and our own build crews, so your ADU moves on a fixed schedule from first drawing to final inspection, across Orange County and Los Angeles.

01 · Architect-grade design: Every unit is drawn around your lot, light and privacy.
02 · Permit-ready, OC-savvy: We know each city’s ADU rules and clear the approvals for you.
03 · Built once, built right: Our own crews deliver on a fixed schedule, foundation to finishes.

Licensed · Insured · Bonded · CSLB #1095476 · Orange County & Los Angeles

Frequently asked questions

What does ADU design-build include?

Design-build means one team is responsible for the ADU from feasibility through final inspection. For L Square, that typically includes site review, concept layout, architectural drawings, structural coordination, Title 24 energy documentation, city submittal, plan-check responses, construction scheduling, inspections and the actual build. The goal is to catch budget and buildability issues while the plans are being drawn, not after an owner has already paid for drawings a builder cannot price cleanly.

Why is design-build useful for ADUs?

ADUs are small buildings with a lot packed into them: kitchen, bath, utilities, HVAC, egress, fire separation, setbacks and rental or family-use goals. When the designer and builder work separately, cost problems often show up late. In design-build, we talk about utility routes, sewer or septic, access, finish allowances and city comments while the plan is still flexible. That usually produces a cleaner scope and fewer surprises.

Do you handle the permit process?

Yes. We prepare the permit set, coordinate engineering and energy documents, submit to the city or county, answer plan-check comments and schedule inspections during the build. We do not promise that every city will approve on the same timeline, because plan check depends on jurisdiction workload and correction rounds. What we do control is submittal quality, fast responses and clear communication when the agency asks for changes.

How do you keep the price from changing after design?

We price from a defined scope: plans, known site conditions, utility assumptions, finish allowances and written exclusions. If a survey, soils report, panel upgrade, sewer issue or field discovery is outside the base scope, we flag it instead of burying it. Owner-driven changes are handled in writing before work proceeds. That discipline is the difference between a realistic construction contract and a vague early estimate.

Is design-build better for a rental ADU or a family ADU?

It works for both, but the priorities change. A rental ADU needs durable finishes, privacy, storage, straightforward maintenance and a layout that fits the local renter. A family ADU may need accessibility, quiet, daylight and easier connection to the main house. Design-build keeps those goals tied to cost and construction details from day one, so the finished unit fits the reason you built it.

Does an Orange County ADU design-build contract include architecture and the city submittal?

Yes. L Square's design-build contract includes site review, concept layout, architectural drawings, structural coordination, Title-24 energy compliance, the City or County submittal package, plan-check responses and construction by our own crews. One accountable team owns the ADU from feasibility through final inspection, so corrections are answered by the same people who drew them rather than forwarded between a separate architect and builder.

How long does an ADU design-build project take under California law?

Under California Government Code Section 66317(a)(3), the permitting agency has 60 days from receiving a complete ADU application to approve or deny it, and the approval itself is ministerial under Section 66317(a)(1) with no hearing and no discretionary review. L Square's design-build schedule front-loads design so the submittal is complete the first time, then runs construction on a fixed timeline from foundation to final inspection.

What does design-build change versus a separate architect and builder on an ADU?

Design-build changes who answers plan check, not the 60-day deadline in Section 66317(a)(3). Under one contract a correction is answered by the people who drew the drawings, instead of being forwarded between an architect and a builder who each wait on the other. For small buildings with kitchens, baths, utilities, egress and fire separation all packed in, that single point of accountability is what keeps discoveries from becoming change orders.

How can a homeowner verify an ADU contractor's license in California?

Enter the contractor's license number on the Contractors State License Board Check A License page at cslb.ca.gov to see the license status and complaint disclosure. CSLB recommends doing this before hiring a contractor or signing a contract. L Square's license number is 1095476, so a homeowner can run the same lookup on us as on every other contractor on the shortlist.

Building an ADU in your Orange County city

ADU rules vary by city. We handle the specifics for your address. Statewide, California allows ADUs up to about 1,200 sq ft with 4-ft side and rear setbacks (CA HCD); your city may add its own details. For the statewide rules, see the CA HCD ADU Handbook.

Irvine ADU rules Anaheim ADU rules Santa Ana ADU rules Huntington Beach ADU rules ADU cost guide All areas we serve

Related guides & articles

ADU cost guide (2026)Honest ranges by type + the 7 things that move the price. California ADU laws 2026What changed this year for Orange County homeowners. OC permit requirementsSubmittals, fees and inspections, city by city. How long does an ADU take?Real timelines by phase: design, permits and build. Casita vs ADUWhat the words mean and how it affects permits. Is an ADU worth it?Rental income, resale value and the real ROI. How to hire an ADU contractorThe CSLB check and what to look for before you sign. What is an ADU?ADU meaning, the four types, and why California made them easy. Above-garage ADUThe apartment over the garage: height rules and the structural truth. Prefab vs custom ADUWhat factory prices leave out, and which lots favor which path. SB 9 vs an ADULot splits explained, and why the ADU usually wins. Building an ADU in Los Angeles?How LA & LADBS differ. Our LA design-build hub.

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