SB 543 – Bigger ADUs Through Smarter Math
More space inside, less confusion outside
SB 543 brings a small but impactful change to how Accessory Dwelling Units (ADUs) are measured in California—using interior livable space instead of exterior wall dimensions. That means slightly larger floor plans, lower development fees in some areas, and more clarity for homeowners and designers alike.
The bill also standardizes Junior ADU (JADU) size limits statewide, clearly defining the maximum as 500 square feet of livable interior space. This consistency makes it easier to design efficient and functional layouts, especially in tight urban lots.
What This Means for You
If you’re planning to:
Add an ADU or JADU to your property,
Maximize space on a narrow or oddly shaped lot,
Or reduce your project’s impact fees or cost per square foot,
SB 543 is great news. By shifting from outer-wall measurements to actual interior livable space, it gives you more usable room within the same footprint—and in some cities, could also lower how your project is assessed for impact fees.
Key Benefits:
More usable square footage within the same allowed footprint,
Lower fees in cities where impact fees are based on livable space,
Clear statewide guidance on JADU sizing—no more jurisdiction-by-jurisdiction confusion,
Easier to design layouts that feel livable, not cramped.
It’s a technical fix, but one that can have real-world impact on how livable, affordable, and flexible your ADU turns out to be.
How New Avenue Homes Can Help
New Avenue has always prioritized designing efficient, elegant ADUs that maximize comfort and value within compact spaces. SB 543 gives us a little more room to work with—and we know how to make the most of it.
Here’s how we help you:
We incorporate updated size rules into every new design, ensuring you get the maximum livable space possible.
We reduce fee exposure by aligning our plans with your city’s definitions for interior square footage.
We specialize in JADU and ADU layouts that feel open and functional—even at 500 square feet or less.
We manage the whole process from site evaluation and zoning to permitting and construction—so nothing is left to chance.
With SB 543 in place, every square foot counts even more—and we’re here to help you make it count.
Want to Build an ADU That Feels Bigger Without Costing More?
Schedule your free consultation today to learn how SB 543—and New Avenue’s smart design approach—can help you create a more spacious, livable ADU that fits your needs and your budget.
