Attached ADU

Attached ADUs in Orange County

An ADU that shares a wall with your home — or sits above your garage — when lot space is tight.

An attached ADU connects to your existing house (or sits above the garage), sharing a wall and often utilities. It’s an efficient way to add a legal unit when a fully detached build won’t fit. Here’s when it makes sense and how it’s permitted.

When attached makes sense

On smaller lots, an attached unit fits where a detached one can’t, usually costs less because it shares a wall and utilities with the main house, and still gives a private entrance and full living space.

The above-garage option

A second-story unit built over the garage adds a full ADU without giving up yard — a popular above-garage ADU layout on tight Orange County lots.

Permits & design

Attached and above-garage units have specific fire-separation and egress requirements; we design to them and clear the city approvals for your address.

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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

Attached vs detached ADU?

Attached shares a wall with your home and suits tighter lots at lower cost; detached is fully separate, more private and higher-rent but usually a larger investment.

Can I build above my garage?

Yes — an above-garage ADU is a second-story unit over the garage. It adds living space without using up yard, subject to height, egress and fire-separation rules we handle.

Is it cheaper than detached?

Often, yes, because it shares a wall and utilities with the main house — though final cost depends on size, finishes and structural work.

Does it share utilities with the house?

It can share connections with the main home, which helps keep cost down; we confirm what your city requires for separate metering.

What are the permit requirements?

Attached units must meet fire-separation, egress and energy (Title-24) codes. We package and clear the full city submittal as part of the build.

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.

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