Start with the basics
California state law requires cities to allow at least one ADU (and often a Junior ADU on top of that) on most residential lots with an existing or proposed single-family home — see our California ADU laws guide for the full statewide framework. That baseline eligibility is broad. What actually varies from property to property is what type and size of ADU your specific lot can support once you factor in existing structures, setbacks, and any overlay zones.
A quick self-check
If you answered most of these with reasonable confidence, an ADU is very likely realistic for your property in some form. If you're unsure about several of them, that's exactly what a property review is for.
What actually rules an ADU out (rare, but real)
A small number of situations make an ADU genuinely difficult or impossible: a lot too small or oddly shaped to meet setback requirements even for a small unit, unresolved code violations or liens on the property, or specific easements and utility rights-of-way that occupy the only buildable space. These are the exception, not the rule — most single-family lots in our service area can support at least a Junior ADU or a garage conversion, even if a larger detached unit isn't realistic.
The difference between "allowed" and "a good idea for you"
Even where an ADU is clearly allowed, whether it's the right move depends on your goals — added rental income, space for family, or long-term property value — and your budget and timeline tolerance. That's a more personal question than a zoning one, and it's worth thinking through before committing to a specific design. Our ADU Opportunity section covers the general reasons homeowners in our service area build.
Get a definitive answer for your specific property
A self-check can tell you whether an ADU is likely realistic. A free property review is how you get a specific answer for your actual address — reviewing your lot, existing structures, and goals against what's realistic, at no cost and with no obligation to move forward.
Frequently asked questions
Most single-family and multi-family property owners qualify for at least one ADU under state law, though the specific type and size that fits depends on your lot. A small number of properties face genuine constraints — very small or irregular lots, unresolved code issues, or easements that occupy the buildable area.
No — many homeowners finance ADU construction through a HELOC, cash-out refinance, or construction loan against equity in a home they're still paying off. See our ADU financing overview for how these options generally work.
A free property review is the most direct path — share your property details and goals, and we'll review them against what's realistic for your lot, at no cost and with no obligation.