ADUs in Southern California
The homeowner's guide to ADUs.
A second unit is one of the best ways to add income, house family, and raise the value of your property. Here is how ADUs work, what California allows, and how we take one from idea to finished home.
- Detached
- Attached
- Garage conversion
- Junior ADU
The basics
What is an ADU?
An accessory dwelling unit is a second, independent home on the same lot as a primary residence. It has its own kitchen, bathroom, and entrance, and can be rented, lived in, or used as a studio or office. California recognizes a few main types.
- 01 Detached ADU
- A standalone structure in the yard, from a compact studio to a full two-bedroom home. The most flexible option when you have the space.
- 02 Attached ADU
- An addition that shares a wall with your existing house. A good fit on tighter lots and hillside sites.
- 03 Garage or space conversion
- Turning an existing garage, basement, or unused part of the house into a legal dwelling. Often the fastest and most cost-effective path.
- 04 Junior ADU (JADU)
- A smaller unit created within the walls of the existing home, up to about 500 square feet, with its own entrance. Frequently allowed in addition to a standard ADU.
The upside
Why build one?
- Rental income
- A well-designed unit can generate steady monthly income. For most owners, this is the single biggest reason to build.
- Room for family
- Aging parents, adult children, or a live-in caregiver, close by but independent.
- Property value
- A permitted, professionally built ADU adds usable square footage and can raise what your property is worth.
- Flexibility
- A home office, studio, or guest house now; a rental or in-law suite later. One building, many lives.
The rules
What does California allow?
California has spent several years making ADUs easier to approve. On most single-family lots, cities must review a complete ADU application on a streamlined, ministerial basis, with no discretionary hearing. Many jurisdictions allow a detached ADU alongside a junior ADU, limit how much size can be restricted, and reduce or remove added parking near transit.
The exact rules, setbacks, height, and utility connections still depend on your parcel and your city. That is why we start every ADU with a feasibility study, so you know what your lot allows before you spend a dollar on design.
The process
How we build an ADU.
- 01
Feasibility
We confirm what your lot allows: zoning, setbacks, utilities, and a realistic budget, before you commit.
- 02
Design
We design a unit that fits the site and your goal, whether that is rental income or space for family.
- 03
Permits & Approvals
We prepare the drawings and shepherd the submittal through your city's review.
- 04
Build
We manage construction and the trades through to a finished, permitted home.
Questions
ADU questions we hear most.
How much does an ADU cost?
Cost depends on the type, size, site conditions, and finish level. A garage conversion sits at the lower end; a larger detached unit on a hillside lot costs more. Rather than quote a number that may not fit your project, we give you a real, all-in budget during feasibility, before you design.
How long does it take?
Plan for a few months of design and permitting, then construction. Conversions move faster than ground-up detached units, and city review times vary. We manage the submittals to keep things moving.
Can I rent out my ADU?
Yes. Renting is one of the most common reasons owners build. Short-term rental rules vary by city, so we will flag what your jurisdiction allows.
Do I need extra parking?
Under current state rules, added parking is reduced or waived in many situations, especially near transit. We confirm the requirement for your address during feasibility.
Will an ADU raise my property taxes?
The new construction is typically assessed and added to your property's value, while your existing home is not reassessed. A tax professional can confirm your specifics.
Do you handle everything, or just design?
Everything. PlantekWest is design-build, so one team handles feasibility, design, permits, and construction, and represents you to the city and the trades.
Free download
The ADU & Custom Build Checklist.
The same checklist we use to pressure-test a project before anyone draws a line. Budget, site, utilities, approvals, and the questions that save you from expensive surprises.
- What makes a lot ADU-ready, and what quietly kills a project
- The permits and approvals to expect, in order
- The questions to ask any designer or builder before you sign
Your checklist is downloading now. We will follow up with a note from the team.
Thinking about an ADU?
Start with a feasibility study. We will tell you what your lot allows, and what it will really cost, before you commit to design.