La Mesa, CA Accessory Structures: ADU Impact Fees (2026)

Section 24.05.020(D)(8)(h)(v) sets a flat rule: no impact fees can be imposed on an accessory dwelling unit smaller than seven hundred fifty square feet. Once an ADU reaches seven hundred fifty square feet or larger, the city can charge impact fees, but only in proportion to the ADU's square footage relative to the primary dwelling unit on the lot, not the standard flat per-unit fee charged on new houses. The code specifically carves connection fees and capacity charges out of the word "impact fee" for this exemption, meaning water and sewer hookup costs are handled under the separate utilities rules in section 24.05.020(D)(8)(g), which likewise exempts most ADUs converted from existing space with independent access from a new utility connection fee unless the ADU is built alongside a brand-new single-family home.

The fee exemption sits inside the ADU chapter that also caps floor area at twelve hundred square feet, sets four-foot side and rear setbacks, and requires the city to approve or deny a compliant application within sixty days without discretionary review. Junior accessory dwelling units get an even broader break: section 24.05.020(D)(9)(j) bars any sewer or water connection fee for a JADU outright, though an inspection fee may still apply. Because impact fees are tied to development impact on citywide facilities rather than the underlying zoning, this exemption applies regardless of which residential zone the ADU sits in, R1 through R3, RB, or R1A.