ADU rules in Fontana

Approved ministerially. Class 1 (state track, Gov. Code sec. 66323): one detached new-construction ADU up to 800 sq ft on a lot with a single-family dwelling; on multifamily lots, up to 2 detached ADUs with a proposed multifamily building or up to 8 with an existing one (not exceeding the number of primary units). Larger detached ADUs, up to 1,200 sq ft, proceed under the Class 2 local standards.

Attached new-construction ADUs are Class 2 (locally regulated): up to 1,200 sq ft but no more than 50 percent of the existing primary dwelling's floor area (800 sq ft protected floor); height up to 25 ft or the underlying zone limit, whichever is lower, maximum two stories. Conversions of existing space inside the primary dwelling are approved under the Class 1 state track.

The code sets no explicit square-footage figure for detached ADUs on multifamily lots; the city ADU info sheet (updated March 2026) lists 850 sq ft, or 1,000 sq ft for units with more than one bedroom, for those, and frames the attached-ADU cap as 50 percent of the main house or 850/1,000 sq ft, whichever is larger, tracking state-law floors. The code text is the operative standard.

ADUs created on or after January 1, 2020 have no owner-occupancy requirement. JADUs require owner occupancy only when the JADU shares sanitation facilities with the primary dwelling; a JADU with its own bathroom carries no owner-occupancy requirement, and the requirement never applies when the property is entirely owned by a government agency, land trust, or housing organization.

The parking standard sits in subsection (g), which applies to locally regulated (Class 2) ADUs; the city's March 2026 info sheet confirms no parking for JADUs and Class 1 units and 1 space with exemptions for attached, Class 2 detached, and multifamily ADUs.

Every ADU and JADU requires an ADU permit and a building permit, considered and approved ministerially without discretionary review or a hearing. Completeness is determined within 15 business days; the City must approve or deny within 60 days of a complete application, and the application is deemed approved if it misses that deadline. Denials must list every defect and how to cure it; completeness and denial appeals go to the planning commission (decision within 60 business days).

The ADU no-separate-conveyance clause cites Gov. Code sec. 65852.26 while the JADU deed-restriction clause cites the recodified Gov. Code sec. 66341; both are quoted as the local text reads.