Custom ADU

Custom ADUs in Orange County

A backyard home designed around your lot, your family and your budget — not a catalog box.

A custom ADU is drawn from scratch for your property — its setbacks, sun, access and how you’ll actually use it — so every square foot earns its place. Here’s how we design, size and build it.

Designed for your lot

We start with your lot’s setbacks, sun path, privacy and access, then shape the unit around them — so it fits the site, protects your main-house views, and makes the most of natural light.

Sizes & layouts

From a compact studio to a full 1,200 sq ft two- or three-bedroom, we design for how the space will be used — a rental that maximizes income, or a multigenerational suite that lives like a real home.

One team, fixed schedule

Architecture, engineering, permits and our own build crews sit under one contract, so your custom design moves on a fixed schedule from first sketch to move-in — with no architect-versus-builder gaps.

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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 can a custom ADU cost in OC?

Custom ADUs cover a wide range because size, finishes and site conditions all move the number. We give you a firm, written quote after seeing your lot — along with financing options — rather than a misleading one-size figure.

How big can I build?

California allows ADUs up to 1,200 sq ft, and at least 800 sq ft is widely permitted regardless of local limits. The right size depends on your lot, budget and whether it’s for rental or family.

Studio vs 1-bed vs 2-bed — what rents best?

It depends on your area and tenant pool. Studios and 1-beds cost less and rent quickly; 2-beds command higher rent and suit families. We help you weigh income against build cost for your lot.

Can you match my main house?

Yes. We design the ADU to complement your home’s style, materials and roofline — or create a deliberate modern contrast if you prefer.

How long from design to move-in?

Most custom ADUs run roughly 6–12 months from first design through permits and construction, depending on size and city timelines.

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

Ready to start
your ADU?

Get a free, no-pressure quote from a licensed Orange County design-build team — and a plan drawn around your lot.

Get your free quote→ (949) 374-7980