Reducing the Cost of ADUs

SB 1117 will make it less costly to build ADUs by removing an arbitrary financial penalty that many jurisdictions impose on ADUs over 750 square feet.

Under current law, an ADU of 750 square feet or less is exempt from most local impact fees. However, in many jurisdictions, ADUs over 750 square feet must pay the full impact fee per square foot – including the first 750 square feet that would otherwise be exempt. The inconsistency makes many ADUs more expensive to build than they would otherwise be.

SB 1117 fixes this by switching to a marginal fee structure. Instead of charging fees based on the entire ADU’s size once it exceeds 750 square feet, local governments can charge proportionally for the square footage above 750 square feet. This reduces a cost barrier that has limited ADU flexibility.

Updates

  • SB 1117 was introduced in the Senate on February 17, 2026.

Author

  • Sabrina Cervantes (SD 31)

Sponsors

  • California YIMBY

Resources