Aliso Viejo, CA Accessory Structures: ADU Rules (2026)

Section 15.14.080 is the City of Aliso Viejo's local ADU ordinance, adopted to comply with state law, and it sorts every project into one of two classes. Class 1 units are approved under Government Code Section 66323 and need only a building permit, filed with the building division along with site plans, floor plans and elevations. Class 1 covers one converted ADU plus one JADU on a single-family lot, and one detached new-construction ADU of 800 square feet of livable space or smaller with side and rear setbacks of at least four feet. On multifamily lots it allows up to eight detached ADUs on an existing multifamily lot, or no more than two on a lot with a proposed multifamily dwelling.

Class 2 units are locally regulated under Government Code Sections 66314 through 66322 and go to the planning division for a development review permit (DRP). That application needs a project narrative, draft deed restrictions and evidence of notice to the HOA, and the city also emails the HOA on record. The DRP is still ministerial, so no hearing is held. The processing fee is set by city council resolution.

Standards for all units include a 16-foot height limit for a detached ADU, 18 feet within one-half mile walking distance of a major transit stop or high quality transit corridor, and 25 feet for an attached ADU. Orange County Fire Authority sprinklers are required in the ADU if the primary residence was required to have them when built. Class 2 units are capped at 850 square feet for a studio or one-bedroom and 1,000 square feet for two or more bedrooms, with four-foot side and rear setbacks, 25-foot front setbacks and 75 percent lot coverage.

The city has 15 business days to rule on completeness and 60 days from a complete application to approve or deny, after which the application is deemed approved unless the applicant asked for a delay. A denial can be appealed in writing to the city clerk, and the Aliso Viejo City Council decides within 60 business days.