A simple guide to building ADUs the right way
Accessory Dwelling Units (ADUs) are a great way to increase the living space, rental income, and property value of your home. With California's push for more housing, it has become easier than ever to build ADUs in the state.
But before embarking on a project, it's important to understand the zoning regulations. These regulations ensure that ADUs are safe, functional, and meet local community standards.
Here is a simple list of the basic requirements for ADU zoning in California.
ADU-Friendly Laws
California has passed several laws to make ADU construction easier, including:
SB 13, AB 68, and AB 881 – These laws streamline approvals, reduce fees, and limit restrictions from local governments.
State vs. Local Rules – While state law sets minimum standards, cities can have additional requirements, so always check local zoning codes.
Where Can You Build an ADU?
ADUs are allowed in most residential zones across California, including:
Single-family zones – Almost all single-family properties can add at least one ADU and one Junior ADU (JADU).
Multi-family zones – Properties like duplexes and apartment buildings can often add multiple ADUs, depending on lot size and existing units.
Lot Size & Coverage
No minimum lot size – State law does not require a certain lot size to build an ADU.Lot coverage rules apply – Your ADU and primary home must not exceed local lot coverage limits (varies by city).
ADU Size Limits
Detached ADUs – Up to 1,200 sq. ft.
Attached ADUs – Up to 50% of your main home’s size (max 1,200 sq. ft.)
Junior ADUs (JADUs) – Up to 500 sq. ft.
Local governments must allow at least an 800 sq. ft. ADU, even if local rules are stricter.
Setback Requirements
Setbacks are the distance between the ADU and your property lines. California law sets minimum setback rules:
Side & Rear Setbacks – At least 4 feet
Front Setbacks – Varies by city
Converted Structures (Garages, Basements, etc.) – Often no additional setbacks required
If you’re converting an existing structure into an ADU, you may be exempt from setback rules.
ADU Height Limits
State Minimum – ADUs must be allowed to reach at least 16 feet in height.
Local Rules Apply – Some cities allow taller ADUs, especially above garages or in multi-story buildings.
Parking Rules for ADUs
Do You Need to Add Parking? Not always! California has reduced ADU parking requirements, and no extra parking is needed if:
Your ADU is within ½ mile of public transit.
The ADU is part of an existing structure (like a garage conversion).
The property is in a historic district.
A car-share service is available within one block.
Even if parking is required, tandem parking (stacked in a driveway) is allowed.
Owner Occupancy Rules
No owner-occupancy required (until 2025) – You do not need to live on the property to rent out your ADU.
This may change in the future, so keep an eye on legislative updates.
ADU Fees & Costs
Impact Fees – If your ADU is under 750 sq. ft., NO impact fees can be charged.
Larger ADUs – Fees must be proportional to the size of your main home.
This rule significantly reduces the cost of building an ADU!
Design & Appearance Rules
Cities may have architectural guidelines to ensure ADUs blend into the neighborhood. These can include:
Roof styles & materials
Exterior colors & finishes
Window placement & design
Some cities have pre-approved ADU designs that speed and simplify the approval process.
Final Thoughts: Making ADU Zoning Simple
Building an ADU in California is easier than ever, but zoning regulations still apply. Understanding the basic rules, such as size restrictions, setbacks, parking and permits, will help you plan your ADU with confidence.
At EG Modern Construction, we specialize in the design, permitting, and construction of ADUs. Our team will take over the zoning process, providing you with a seamless and enjoyable experience.
Need help with zoning and ADU building permits? Contact us today for a free consultation and let's make your ADU project a reality!