Building an ADU
in Orange County.

What is an ADU?

An accessory dwelling unit (ADU) is a secondary, self-contained home built on a lot that already has a primary residence. Also called a granny flat, in-law suite, backyard cottage, or casita, an ADU has its own kitchen, bathroom, and private entrance — a complete second home on your property.

Homeowners across Orange County build ADUs for rental income, multi-generational living, a private home office, or simply to add long-term value to their property. Thanks to relaxed California state laws and streamlined local permitting, building an ADU has never been more accessible.

Types of ADUs we build

Every property is different. We design and build the full range of ADUs, tailored to your lot, budget, and goals.

Detached ADU

A standalone backyard home, fully separate from the main house — the most private and flexible option.

Attached ADU

An addition connected to your existing home, sharing one wall — efficient on tighter lots.

Garage conversion ADU

Transform an existing garage into a finished, permitted living space — often the most affordable route.

Junior ADU (JADU)

A compact unit up to 500 sq ft created within your home's existing footprint.

Above-garage ADU

A unit built over a garage to add space without giving up yard.

Guest house & casita

A luxury detached suite for guests, family, or a short-term rental.

How much does an ADU cost?

The cost of building an ADU in Orange County depends on its size, design complexity, type, finishes, and site conditions. A garage conversion is typically the most affordable path, while a custom detached unit with premium finishes sits at the higher end.

Rather than a one-size-fits-all number, we give you an accurate, custom quote based on your lot and goals — along with financing options to make your project achievable, with no surprises along the way.

Get your free, custom quote →

How long does it take?

Most ADUs in Orange County take about 6 to 12 months from first design to move-in. Smaller garage conversions move faster; custom detached units take longer due to design and permitting. A typical timeline:

• Design & 3D plans — Weeks 2–5
• Permitting & city approvals — Weeks 5–13
• Construction — Months 4–8
• Final inspection & move-in — Final weeks

Permits & legal requirements

Building an ADU in California requires adherence to state ADU law and local zoning codes — including limits on unit size, setbacks from property lines, and parking. Many Orange County cities have streamlined ADU permitting to ease the housing shortage, and recent state laws have made approval faster than ever.

As a licensed ADU construction company (CSLB #1095476), we package, submit, and clear every city correction — structural, energy, and utilities — so you never have to navigate the Orange County planning department alone.

Benefits of building an ADU

Rental income

A long- or short-term rental that helps offset your mortgage in one of California's most expensive markets.

Increased property value

ADUs add livable square footage and attract buyers seeking rental or multi-generational potential.

Multi-generational living

Keep aging parents or adult children close — with independence and privacy.

Flexible space

A home office, studio, gym, or guest suite that adapts to your life.

Faster approval

Many cities streamline ADU permits compared to new construction.

Sustainability

A smaller footprint and energy-efficient design lower long-term costs.

Why build with L Square

L Square Construction is a licensed accessory dwelling unit contractor serving Orange County and Los Angeles. We handle architecture, structural engineering, interior design, permitting, and construction in-house — one team, one contract, from your first call to your front-door key.

Every build comes with precision craftsmanship, transparent pricing, and weekly progress updates — so you always know exactly where your project stands.

Licensed · Insured · Bonded · CSLB #1095476