Two rental units. One detached building. One permit.

If your lot already has a building with two or more attached dwelling units, yes — California Gov. Code § 66323(a)(4) entitles you to add detached ADUs equal to your existing unit count, up to eight, and HCD has confirmed those ADUs do not have to be detached from each other. That means one detached duplex building counts as two ADUs. If you have a single-family house instead, you are on a different pathway: one detached ADU, one conversion ADU, and one JADU. Full rules are on our multifamily ADU guide.

Architectural plans, structural engineering, Title 24 energy compliance, and permit processing through to issuance. What is not included: city plan check and permit fees, which you pay directly at cost, plus any soils or survey reports your jurisdiction requires. Construction is quoted separately by a licensed general contractor.

Because construction cost is genuinely site-specific on a multi-unit building — utility runs, site access, grading, and existing service capacity vary far more than they do on a single backyard ADU. Publishing one fixed build number across every lot would be a number we would have to renegotiate. The plan fee is fixed. The construction range shown is an estimate from an independent licensed GC and gets firmed up once we have your site conditions.

Sixteen feet is the base. You get 18 feet if your existing multifamily building is multistory, or if the property is within a half-mile walking distance of a major transit stop or high-quality transit corridor. Twenty feet is available only through the transit pathway, with a roof pitch matching your primary building. This is the single fact that determines whether the stacked plan is available to you, and it is the first thing we check.

No. Local agencies may not impose parking requirements on ADUs created under Gov. Code § 66323. You are also not required to replace parking you remove — if you demolish a garage or carport to make room, no replacement is required. One caution specific to tenanted Los Angeles properties: taking a parking space from an existing tenant on an RSO property may require a corresponding rent reduction.

The agency must determine whether your application is complete within 15 business days, then approve or deny within 60 days of a complete application. Miss the 60 days and it is deemed approved by operation of law. Review is ministerial — no public hearing, no design review. The practical variable is completeness, which is where multi-unit projects lose time.