- Dax NollenbergerWait… You Can Potentially Have FOUR ADUs on a Single-Family Property in Santa Cruz County?
Most homeowners, Realtors, and even many contractors still believe the rule in California is simple:
- One ADU
- One Junior ADU (JADU)
For years, that was essentially the standard understanding.
But California quietly expanded ADU laws several times over the past few years, and the rules are now far more aggressive than most people realize.
In fact, according to Santa Cruz County, certain single-family parcels may potentially support up to four accessory dwelling units in addition to the primary home.
That sounds almost impossible at first, so let’s break down how this actually works in plain English.
The Original Rule: One ADU + One JADU
This is still the foundation of California ADU law.
On most single-family residential lots, state law allows:
- One standard ADU
- One JADU
A JADU is a smaller unit created within the walls of the primary house and is typically limited to 500 square feet.
This is the version of the law most people are familiar with.
But then California added another layer.
The Part Most People Don’t Know About: “State Exempt” ADUs
California Government Code 66323 created additional ADU categories that local governments are required to approve ministerially if they meet certain standards.
These are often referred to as:
- “State exempt ADUs”
- “66323 units”
- “By-right ADUs”
Santa Cruz County explains it this way:
“One ADU subject to all the requirements of state law and local ADU regulations, and multiple ADUs subject only to the requirements of Government Code 66323…”
That distinction is incredibly important.
Essentially, California separated ADUs into:
- Standard/local ADUs
- Additional state-protected ADUs
And in some cases, they can stack together.
So How Could Someone Potentially Have Four ADUs?
Here’s the simplified version.
A single-family property could potentially have:
1. One Standard ADU
This is the “normal” ADU most people think about:
- Detached backyard cottage
- Attached ADU addition
- Larger custom ADU
This unit is generally subject to more local development standards.
2. One Conversion ADU
This usually means converting existing space such as:
- A garage
- Basement
- Existing accessory structure
- Portion of the house
Because the structure already exists, California limits how much local governments can restrict it.
3. One JADU
A smaller unit within the primary residence itself.
4. One Detached “State Exempt” ADU
California now requires local governments to allow:
- One detached ADU
- Up to 800 square feet
- With only 4-foot setbacks
- Approved ministerially if it meets state standards
This is where the law became much more aggressive.
Even if local zoning would normally restrict the project, the state heavily limits the County’s ability to deny qualifying units.
So Does Zoning No Longer Matter?
Not exactly.
This is where many people get confused.
California weakened local zoning control over ADUs significantly, but zoning and property constraints still matter in the real world.
The state mostly removed discretionary barriers.
It did NOT remove:
- Septic limitations
- Fire access requirements
- Coastal restrictions
- Environmental review
- Utility capacity
- Physical lot constraints
- Building code requirements
And in Santa Cruz County, those issues are often the real limiting factor.
A property may technically qualify for multiple ADUs under state law while still being completely impractical to develop due to:
- Steep terrain
- Septic upgrades
- Fire access
- Construction costs
- Coastal Commission issues
- Limited usable area
So the legal maximum and the realistic maximum are often very different.
Why Most People Have Never Heard This
There are a few reasons:
- California’s ADU laws changed rapidly over several years
- Different jurisdictions interpreted the laws differently
- Many professionals still operate under the old rules
- Most properties physically cannot support the maximum density anyway
- The economics often do not pencil out
Even today, many homeowners, Realtors, and contractors still think “one ADU plus one JADU” is the hard cap.
But California’s current ADU laws are substantially more expansive than most people realize.
What This Means for Santa Cruz County Property Owners
For some properties, these newer laws may create opportunities that simply did not exist a few years ago.
For others, the physical limitations and costs may still make additional units unrealistic.
But understanding what is actually allowed is becoming increasingly important, especially for:
- Investors
- Multigenerational families
- Owners looking for rental income
- Buyers evaluating development potential
- Owners considering legalization of existing spaces
The key is understanding the difference between:
- What state law theoretically allows
versus - What a specific property can realistically support
If you own property in Santa Cruz County and are curious what may actually be possible under current ADU laws, feel free to reach out. I’d be happy to help point you toward the right resources and professionals to better understand your property’s potential before you spend significant money pursuing plans or permits.
Santa Cruz County ADU Resources:
Dax Nollenberger
📩 dax@sereno.com
📞 831-227-5847
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