SB 543 could streamline ADU construction across California

California continues to look for solutions to its housing crisis, and accessory dwelling units (ADUs) are at the center of many proposals. A new bill, SB 543, introduced by Senator Jerry McNerney, aims to make building both ADUs and junior ADUs (JADUs) simpler and more consistent statewide.

‍

In late August, the California Assembly approved the measure, moving it to the Senate floor for a final vote before potentially reaching the Governor’s desk.

‍

Why ADUs are part of the solution

‍

ADUs have been steadily growing in popularity as a flexible housing option. These small units, often built in backyards or converted from garages, can provide affordable rental opportunities, multigenerational living, or extra income for homeowners.

‍

According to the California Department of Housing and Community Development, ADUs are one of the fastest ways to add housing in already developed areas. Recent changes in state law have removed many of the barriers that once made it difficult to build them, leading to a surge in applications across major cities like Los Angeles, San Diego, and San Jose.

‍

What SB 543 proposes

‍

SB 543 builds on earlier reforms by tightening up statewide rules and reducing local red tape. Here are some of the key points:

• Size limits: Junior ADUs would be capped at 500 square feet. ‍
• Faster approvals: Cities and counties would have to review ADU and JADU applications promptly and provide clear feedback if anything is missing, instead of dragging projects through lengthy hearings. ‍
• State rules over local rules: If local standards are too strict, state law would override them. At minimum, homeowners would always have the right to build an 800-square-foot ADU with four-foot setbacks. ‍
• Clear fee rules: Small ADUs and JADUs would not be subject to impact fees. Larger ADUs could only be charged fees in proportion to their size compared to the main house. ‍
• Stronger state oversight: Local ordinances would have to be reviewed by California’s Housing and Community Development Department (HCD) to ensure compliance.

By setting consistent rules, the bill is intended to cut through the patchwork of regulations that often frustrate homeowners and slow down construction.

‍

Why SB 543 matters

‍

Accessory dwelling units have become one of the fastest-growing housing types in California over the past decade, largely due to state laws passed since 2016 that reduced barriers to construction (California Department of Housing and Community Development, 2024). SB 543 builds on this momentum by proposing additional changes to standardize rules across cities and counties.

‍

By reducing local variations and delays, the bill aims to ensure that homeowners have a clearer, more predictable path to building ADUs or JADUs on their properties. Supporters argue this could speed up production of much-needed affordable housing units, particularly in areas struggling with rising rents and limited supply.

‍

Timeline & Next Steps

‍

• August 28, 2025: The Assembly approved SB 543, moving it closer to becoming law. ‍
• Next stop: A final vote on the Senate floor. ‍
• If approved: The bill will head to Governor Gavin Newsom’s desk for signature.

‍

If SB 543 passes, it would go into effect statewide and give homeowners a clearer, faster path to adding ADUs or JADUs to their properties.

‍

Quick Tip: If you’ve been considering adding an ADU, keep an eye on SB 543. Should it pass, the permitting process could become more predictable — and potentially less costly across California.

‍

Xavier Rodriguez is the CEO of ADU Geeks, San Diego’s leading ADU consulting and project management firm. In 2024, the company was ranked No. 1 on the San Diego Business Journal’s Fastest Growing Private Companies list in the Small Business category, achieving 594.3% revenue growth.