Should I use a preapproved ADU plan?

A preapproved or standard ADU plan is a repeatable building design that an agency has already reviewed through its program. It is not permission to build on a particular parcel. The useful homeowner question is not simply whether a catalog exists; it is whether an active plan fits the correct jurisdiction, the property constraints, the household brief, the plan-use rights and the total site-specific scope. Start by confirming the authority in the permit directory, then compare the parcel and project paths in the ADU decision guide.

What preapproval covers—and what it does not

Program terminology varies, but the reviewed local materials separate the repeatable building design from parcel-specific approval. A homeowner still needs the responsible agency's current application, site or plot plan, zoning review, foundation response, utility coordination, energy documentation and any property-specific clearances. Agency fees may still apply. Plan acquisition or license terms may also apply when a private designer owns the drawings.

• —Potentially reusable: the reviewed architectural and structural design identified by the program and code cycle.
• —Still site-specific: boundaries, setbacks, height, lot coverage or FAR, easements, existing structures, access and mapped constraints.
• —Still coordinated: foundation and soils response, utility routes and capacity, sewer or septic, drainage, Title 24 and assigned agency referrals.
• —Still a budget question: plan rights, site adaptation, consultants, plan check and permit fees, site work, construction, contingency and exclusions. Use the budget workflow to keep these lines separate.

Beverly Hills: designer-owned plans that remain site-specific

The City of Beverly Hills describes its listed detached-ADU plans as approximately 70% complete for permitting. The designers own the plans, and a homeowner works directly with the selected designer. The City's property-owner checklist still calls for a building-permit application and site information covering items such as property lines, setbacks, easements, parking, utilities, sewer, drainage, sprinklers and emergency access. The City warns that a listed plan may not suit every site or condition.

Before purchasing, ask the designer what the price includes, what project-use license is granted, who prepares and signs site-specific documents, and what happens if the layout, exterior or structure changes. The reviewed City materials do not support assuming that a modified design keeps the same preapproved treatment.

City of Los Angeles: check the live LADBS catalog

LADBS publishes an Approved ADU Standard Plans catalog with city-provided and privately owned entries. Catalog and code-cycle status can change, so verify the chosen plan on the current LADBS listing rather than relying on a saved marketing page. Private plans require coordination with their owner; LADBS identifies its city-provided YOU-ADU plan separately.

LADBS states that possession of a Standard Plan does not waive the building permit. The City still reviews site-adaptation documents, zoning, foundation information and the items in its current ADU building-permit checklist. Confirm proposed changes with both the plan owner and LADBS before treating the project as eligible for that path.

Unincorporated LA County: County plans with fixed modification rules

LA County publishes County-owned Plans A, B and C for homeowners in unincorporated territory. The official materials identify the plans as free to use, but site work, professional services, agency fees, permits and construction are separate. Regional Planning must approve a property-specific plot plan, and Public Works identifies site-specific Title 24 calculations and agency referrals among the remaining work.

The County says these plans cannot be revised and must be permitted as designed, while orientation changes and mirrored floor plans are allowed. That makes desired alterations an early go-or-no-go question. First verify that the parcel is actually unincorporated County territory; a postal city name is not enough.

What a design change can affect

A change can affect more than drawing time. It may alter the plan owner's license, the set that was reviewed, structural and energy coordination, foundation assumptions, product specifications and the agency review path. The exact consequence depends on the program and plan. Get the answer in writing before paying for a plan or using its status in a budget or schedule.

The limited California timing rule

Government Code § 65852.27 requires local preapproval programs and includes a 30-day approval-or-denial rule for a qualifying detached ADU application using a plan preapproved within the current code-adoption cycle—or a plan identical to one used in an application approved within that cycle. The rule is conditional. It is not a universal promise for attached units, altered plans, incomplete submissions, every catalog entry, permit issuance, utility work or construction.

A cautious hypothetical comparison

Suppose a homeowner likes a listed two-bedroom plan but needs to move windows, change the roof and shift structural openings. The catalog option might still be useful as a reference, yet those changes could affect plan rights and review treatment. Compare written answers for the unchanged catalog plan, the modified version and a custom design; include site adaptation, foundation, utilities, energy work, fees and construction in each scope. Do not compare only the catalog-plan price.

Questions to resolve before selection

1. 01Which agency has permit authority, and is the plan active in that agency's current catalog and code cycle?
2. 02Who owns the drawings, what use license is included, and who may modify, stamp and submit them?
3. 03Does the documented footprint fit surveyed boundaries, setbacks, easements, coverage or FAR, access and existing structures?
4. 04Which foundation, soils, energy, fire, utility, drainage and referral documents remain property-specific?
5. 05Which desired changes are allowed, and what would each change do to plan rights and agency review?
6. 06Which costs are known, allowances, excluded or unknown across plan acquisition, adaptation, fees, site work and construction?

Bring the address, assessor parcel number, jurisdiction evidence, survey or dimensioned site information, permit history, known easements and overlays, utility records, household brief, preferred catalog entry and unresolved budget lines to a feasibility conversation. RSA can help organize those questions; only the responsible agency and relevant professionals can determine parcel-specific requirements and approvals.