Pre-Approved ADU Plans in California

What are pre-approved ADU plans?

A pre-approved ADU plan is a building design that has already been reviewed by a local jurisdiction for code compliance. You may also see the same general idea described as shelf-ready, permit-ready, pre-reviewed, or pre-engineered, but those phrases are not always used the same way.

The key point is that pre-approval applies to the building design. It does not mean your entire project is approved for your specific property. Your lot still needs site-specific review for placement, utilities, foundation conditions, energy compliance, fees, and other local requirements.

For California homeowners, the phrase usually has three different meanings. First, a city or county may publish a shelf-ready catalog of pre-reviewed ADU plan sets. Second, AB 1332 created a statewide preapproval pathway where plans can be submitted once and reused on multiple lots. Third, a builder or manufacturer may offer standardized, pre-engineered models that reduce custom-design work even when the local permit still has to be processed.

How does California's AB 1332 pre-approval program work?

AB 1332 added Government Code section 65852.27. It requires every California city and county to establish a program for the preapproval of ADU plans by January 1, 2025.

The law does not let a local agency limit who can submit plans for preapproval. Homeowners, architects, engineers, designers, and ADU companies can all submit plans. Once a plan is preapproved, the agency must post the preapproved plans and the submitter's contact information on its website, and it must remove a plan within 30 days if the submitter asks for removal.

AB 1332 also improves the permit review timeline in a specific situation. If a complete application is for a detached ADU and uses a preapproved plan, or a plan identical to one the agency approved during the current triennial code cycle, the agency must approve or deny the application within 30 days. That is faster than the standard ministerial ADU review baseline, which is 60 days for a complete application.

The 30-day rule is not a blanket promise for every ADU. It depends on the project being a detached ADU, using an eligible preapproved or identical plan, and being submitted as a complete application.

See also:Read the statewide ADU law guide Use this for the broader California ADU rules that sit alongside AB 1332.

How much faster and cheaper is a pre-approved plan?

A pre-approved plan can reduce the time spent on building-design review because the plan has already been checked for code compliance. In real projects, market experience often puts plan check for a preapproved plan around 4 to 6 weeks instead of using the full 60-day review window, but homeowners should verify timing with the specific city or county.

The larger savings may be before permit submittal. A shelf-ready or standardized plan avoids a full custom-design phase, so it can cut design time and design cost. The tradeoff is that the plan may not fit every lot, family need, rental strategy, or architectural preference.

Custom design can still make sense when the site has tight constraints, the homeowner wants a specific layout, or the ADU needs to match an existing home closely. Pre-approved plans work best when speed, predictability, and a known layout matter more than one-off design flexibility.

See also:Compare ADU timeline steps Use this to understand where permitting fits into the full project schedule. · Compare ADU cost drivers Use this to separate design cost from construction, utility, permit, and site costs.

Which Sacramento-area jurisdictions offer pre-approved or shelf-ready plans?

The City of Sacramento runs a Preapproved Accessory Dwelling Units (AB-1332) program through its Community Development and Building division. Sacramento County has also launched a Shelf-Ready ADU Program, live since 2025: a set of free, pre-reviewed detached ADU plans (from a ~460 sq ft studio up to a 1,184 sq ft three-bedroom), funded by a state HCD grant and available for unincorporated-county properties.

Those are examples of the first meaning of pre-approved plans: a local catalog or shelf-ready program. They are useful because homeowners can start from a plan set the jurisdiction has already reviewed rather than commissioning a fully custom building design first.

Other California cities and counties must also have a plan preapproval program under AB 1332. That does not always mean a homeowner will find a large ready-made catalog on day one. The legal requirement is a preapproval pathway, and agencies must post preapproved plans and submitter contact information on their websites.

Sacramento-area homeowners should confirm the current local program page before choosing a plan. City boundaries, county jurisdiction, special districts, utilities, and site conditions can change what has to be submitted even when the ADU design itself is preapproved.

See also:Check Sacramento ADU rules and permits Use this for local permitting context before choosing a plan. · Check Placer County ADU rules · Check El Dorado County ADU rules · Check Yolo County ADU rules

What does a pre-approved plan not cover?

A pre-approved plan does not approve the ADU for your lot by itself. It only means the building design has already cleared the jurisdiction's plan check for code compliance.

Your project still needs a site plan showing where the ADU will sit on the property. The jurisdiction still has to review the project against the specific lot, including placement and any documents required for that site.

Foundation and soils work may still be required where the jurisdiction or site conditions call for it. A plan that works structurally as a repeatable design still has to be connected to the real ground conditions of the property.

Utility work is also site-specific. Water, sewer, and electrical connections depend on the existing property conditions, local utility requirements, and the way the ADU is placed on the lot.

Title 24 energy compliance is still reviewed for the specific project. Permit fees and any applicable impact fees also still apply. A pre-approved plan can reduce design and review friction, but it does not remove the permit process.

Should you use a pre-approved plan or a custom design?

Use a pre-approved or standardized plan when the layout works for your lot and your priority is reducing design time, design cost, and avoidable permit review friction. This path is strongest when you want a proven ADU design and do not need major customization.

Use a custom design when the property is constrained, the ADU needs a special layout, or the exterior has to respond closely to the main home. Custom work can be the better fit when design control matters more than speed.

Upside's productized ADU models fit the third meaning of pre-approved plans: builder pre-engineered plan sets. They are standardized designs built to reduce the custom-design phase. A local jurisdiction still has to review the project for the specific lot, and homeowners should verify the local permit path before relying on any timeline estimate.

For many Sacramento-area homeowners, the practical question is not simply pre-approved versus custom. It is whether a repeatable plan can pass the real property constraints: setbacks, access, utilities, foundation assumptions, energy compliance, and budget.

See also:View Upside's productized ADU models Use this to compare standardized model options. · See published ADU pricing Use this to understand budget ranges before selecting a plan path. · Review the ADU process Use this to see how feasibility, design, permitting, and construction fit together. · Request a free feasibility check Use this to confirm whether a pre-approved or standardized plan fits your lot.