One-time fees charged by cities to fund infrastructure (roads, schools, water, sewer) impacted by new development.
California state law now bars impact fees on an ADU with 750 sqft or less of interior livable space; SB-13 began that impact-fee limit in 2020, and the current code uses the 750-sqft-or-less line. Any impact fees charged on larger ADUs must be proportional to the primary dwelling (typically $4-$30 per sqft where charged); from January 1, 2027, for up to two ADUs on a lot, they may be charged only on the area above 750 sqft. School fees follow a different rule: for Education Code section 17620 purposes, an ADU or JADU with less than 500 sqft of interior livable space is treated as not increasing assessable space by 500 sqft; a school district may charge above that if otherwise authorized.
Part of the BackyardADU California ADU Glossary — plain-English definitions of the regulatory, construction, and financing terms you'll encounter during a California ADU project.