ADU & SB 9 Guide
Straight answers about Accessory Dwelling Units and California SB 9 duplexes and lot splits, for property owners in Los Angeles County and Ventura County.
What is an ADU (Accessory Dwelling Unit)?
An Accessory Dwelling Unit, or ADU, is a secondary, independent housing unit built on the same lot as an existing single-family or multi-family home. ADUs can be detached (a standalone structure in the backyard), attached to the main house, or converted from existing space such as a garage. In California, an ADU must include its own kitchen, bathroom, and separate entrance, and can be used for family members, long-term tenants, or rental income.
What is SB 9, and how does it apply in Los Angeles and Ventura Counties?
California Senate Bill 9 (SB 9) is a state law that lets eligible single-family lots be split into two parcels, developed with up to two primary residential units per parcel, or both, allowing up to four units total on a property previously zoned for one. SB 9 applies statewide, including throughout Los Angeles County and Ventura County, but individual cities can still apply their own objective zoning standards, such as setbacks, minimum lot size, and parking, on top of the state law. Because these local standards vary by jurisdiction, every SB 9 project should be evaluated against the specific city or county code that applies to your parcel.
Do I need to hire an architect before I can get a cost estimate for my ADU?
No. Brick by Brick Builders uses 3D Revit modeling and photorealistic renderings to draft your floor plans and visualize your project before you commit to paying for a full architectural and engineering plan set. This design-first approach lets you see and adjust your layout early, so you only move into heavier engineering costs once your vision is locked in.
How long does ADU permit approval take in California?
State law requires local jurisdictions to ministerially review complete ADU applications within 60 days in most cases, without a public hearing. Actual timelines can still vary depending on how complete the submitted plans are, the specific city or county's workload, and whether the project also requires other approvals, such as an SB 9 lot split. We manage the permit submission and city coordination process on your behalf to keep your project moving.
What is the difference between an ADU and a Junior ADU (JADU)?
A standard ADU is a separate housing unit, either attached or detached, with its own full kitchen and bathroom. A Junior ADU (JADU) is smaller, generally up to 500 square feet, and is created within the walls of an existing single-family home, typically sharing at least a bathroom with the main house and including an efficiency kitchen. A JADU is often a lower-cost path to adding rentable or family living space when new square footage isn't needed.
Can I combine an ADU with an SB 9 lot split or duplex project?
In many cases, yes, though it depends on your lot's size, zoning, and the specific rules of your city or county, since ADU law and SB 9 are separate legal pathways that can interact differently depending on the jurisdiction. Because these rules are technical and site-specific, we recommend a free on-site consultation so we can evaluate your parcel's actual zoning and confirm which combination of ADU, JADU, and SB 9 options is available to you.
Do I have to live on the property to build an ADU or use SB 9?
Owner-occupancy requirements have changed more than once at the state level in recent years and can also vary by local ordinance, so this is one of the details we confirm against current code before your project moves forward. It should not be assumed either way from general information alone.
How much does it cost to build an ADU or SB 9 duplex in LA or Ventura County?
Cost depends on unit size, finish level, site conditions such as utility connections and grading, and local permit fees, so we don't publish a single flat rate. Because we design your 3D floor plans before you commit to heavy engineering costs, you'll have a clear, visualized scope to base your budget on before major spending begins. A free on-site visit is the fastest way to get a project-specific estimate.
What technology does Brick by Brick Builders use to plan a project before construction begins?
We use Autodesk Forma for early site feasibility, lot placement, and microclimate analysis; Revit for detailed 3D floor plans and photorealistic renderings; and Navisworks to detect structural and trade clashes on screen before they become costly field errors.
Who do I contact to start my ADU or SB 9 project?
Schedule a free on-site consultation and 3D design conversation with our team. We'll evaluate your property, walk through local zoning rules, and outline your options, with no upfront architect fees.
Have a question about your specific property?
Read more about our design-build process on the About page, or talk to our team directly.
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