A pre-approved plan still needs a plan of the lot
A pre-approved ADU program lets an owner pick a building design the city has already reviewed. The catalog cannot know the lot: where the unit sits, how far it stands from each lot line and from the house, and how it is reached. The programs whose own pages were read for this guide say so. Phoenix states that "A plot/site plan will still be required for permitting" [1]. Scotts Valley says its plans "may not stand alone and must be integrated with a specific site" [2]. Pasadena makes preparing the site plan Step Two of its ADU Standard Plans Program [7].
So the plan set for a pre-approved ADU has two parts: the building, which the catalog supplies, and the site plan, which is drawn for the one lot [5, 7]. The site plan items the cities name are compared in ADU site plan requirements.
The state laws behind the catalogs
California and Arizona both require their cities to run pre-approved plan programs, on different terms [3, 4].
California. Gov. Code 65852.27, added by AB 1332 (2023) and cited as read on October 10, 2026, says each local agency "shall accept accessory dwelling unit plan submissions for preapproval," and the programs were due Jan 1, 2025 [3]. An application for a detached ADU that uses a preapproved plan is decided within 30 days [3]. SANDAG's guidance on the section ties the plans to the state ADU law, citing Section 66313 [8]. California's catalogs are run by its counties and cities, several of them under this section, as the table below shows [2, 9, 10, 11, 12].
Arizona. ARS 9-461.19, enacted by SB 1529 (Laws 2025, chapter 259) and cited here from the enacted text pending codification, as read on October 10, 2026, sets a schedule in two steps [4]. From July 1, 2026, municipalities post Class 4 ADU plans at 200, 600 and 1,000 sq ft, with three elevation options in each class [4]. From Jan 1, 2027 the catalog adds Class 2 and 3 duplex and triplex plans at 400 to 1,000 sq ft per unit [4]. Approval of a submitted plan is administrative, without discretionary review [4]. Arizona's wider rules are on the Arizona site plan page.
Rules that follow a chosen plan
The programs differ less on the building than on the rules attached to it.
- Who may submit a plan. Scotts Valley takes detached ADU plans from licensed professionals [2], and San Ramon from qualified professionals [9]. SANDAG reads California's section as open to any party [8], and under 9-461.19(B)(2) an Arizona municipality "may not restrict who may submit" [4].
- Changes to the plan. In San Ramon any modification disqualifies the plan [9], and Phoenix's library plans must be used "as is" [1].
- The code cycle. A Scotts Valley plan is submitted to the current code cycle and its listing stays for that cycle, during which its licensing fees "may be sold repeatedly until the end of the code cycle" [2]. San Ramon lists a plan with the vendor's contact until new codes are adopted [9].
- Contact details and removal. Both statutes put the applicant's contact information beside the posted plans [3, 4], and an Arizona municipality removes a plan within 30 days on request [4].
- Indemnity. SANDAG notes that a California agency may require an indemnification agreement [8], and Arizona's statute lets a municipality require an indemnity [4].
These are the cities' and the states' programs. An owner picks a plan from the city's catalog or from a designer the catalog lists with contact details [3, 9]; the site plan is the part drawn for the lot.
The catalogs compared
| Program | Basis | What it offers | The lot |
|---|---|---|---|
| Scotts Valley, California | AB 1332 [2] | Detached ADU plans from licensed professionals, listed for the current code cycle [2] | Each plan integrated with a specific site [2] |
| San Ramon, California, Permit Ready ADU | AB 1332 [9] | Plans from qualified professionals, listed with the vendor's contact [9] | The ADU application names the designer and the model [9] |
| Sonoma County, ADU Ready | AB 1332 [10] | Pre-reviewed detached ADU plans [10] | Not stated in the program page read |
| Del Norte County, California | AB 1332 [11] | Designer applications, and a county-owned 600 sq ft plan offered free [11] | Not stated in the program page read |
| Hidden Hills, California | AB 1332 [12] | A program in which "no plans have been preapproved" [12] | No plan to place yet |
| Los Angeles, DBS Standard Plan | Local program [5] | Approved standard plans [5] | A copy of the approved plan, a title sheet and a plot plan with 9 items [5, 6] |
| Pasadena, ADU Standard Plans | Local program [7] | City standard plans [7] | Step Two: prepare the site plan [7] |
| Redwood City, California | ADU ordinance and completeness checklist [13] | A completeness checklist that covers pre-reviewed plans [13] | The checklist asks for the ADU's placement on the lot [13] |
| Phoenix, ADU Standard Plan Library | 2024 City of Phoenix and AIA Phoenix Metro Design Competition [1] | Competition entries, free to residents [1] | A plot or site plan still required [1] |
City context is on the Los Angeles, San Diego and Phoenix metro pages, and California's statewide rules on the California site plan page.
Fitting a catalog plan to the lot
A catalog fixes the footprint, and the lot has to take it. Because San Ramon disqualifies a modified plan [9] and Phoenix's plans are used as is [1], a plan that does not fit a lot in those programs is swapped for another plan rather than edited. The site plan is where that test is made, before the application: the footprint against the side and rear setbacks, the distance to the house, the driveway and walks, the utilities and any easement.
State numbers set the edges of that test, California's cap of 4 ft on side and rear setbacks among them (Gov. Code 66314(d)(7)) [14]. The California geometry is drawn in California ADU site fit, and the state rules are tabled in the ADU laws by state guide.
The studio draws that site plan: the lot lines, the house, the chosen plan's footprint as approved, and the dimensions, access and areas the city's checklist asks for. The plan is preliminary and carries no engineering layer; drainage, grading and utility design are by your engineer of record. The decision clocks above belong to the statutes, and the site plan does not change them. Who may draw each sheet is set out in who can draw ADU plans, the other residential plans are under permit site plans, and the background essay is how ADU legislation is reshaping single-family site plans.
To have the site plan drawn for a pre-approved ADU on your lot, start a project and choose "Residential: ADU (accessory dwelling unit)" as the project type; attach one file, the most useful you have: a survey, or a sketch with measurements, and name the catalog plan you picked under program and stage.
Frequently asked questions
Do I need a site plan if I use a pre-approved ADU plan?
How fast must a California city decide a pre-approved ADU?
An application for a detached ADU that uses a preapproved plan is decided within 30 days under Gov. Code 65852.27, added by AB 1332 (2023) [3].
What sizes are Arizona's pre-approved ADU plans?
Class 4 ADU plans at 200, 600 and 1,000 sq ft, each with three elevation options, posted from July 1, 2026; Class 2 and 3 duplex and triplex plans follow from Jan 1, 2027 at 400 to 1,000 sq ft per unit (ARS 9-461.19) [4].
Can I change a pre-approved ADU plan to fit my lot?
Who can submit plans to a pre-approved ADU program?
Do pre-approved ADU listings expire?
In some programs they run with the building code cycle. A Scotts Valley plan is listed for the code cycle it was submitted to [2], and San Ramon keeps a plan listed until new codes are adopted [9]. The cycle in force is named on city handouts: Milpitas's handout on plans required to be designed by an architect or engineer cites the 2025 California Building Code [15].
Sources
- 1)Accessory Dwelling Units (ADU): ADU Standard Plan Library, City of Phoenix Planning and Development. Accessed 2026-10-10.
- 2)AB 1332: Pre-Approved ADU Program, City of Scotts Valley, California. Accessed 2026-10-10.
- 3)AB 1332, Accessory dwelling units: preapproved plans (Gov. Code 65852.27), California Legislature. Accessed 2026-10-10.
- 4)Laws 2025, Chapter 259 (SB 1529): ARS 9-461.19, pre-approved plans, Arizona State Legislature. Accessed 2026-10-10.
- 5)ADU Standard Plan Program: approved standard plans, Los Angeles Department of Building and Safety. Accessed 2026-10-10.
- 6)ADU Standard Plan Building Permit Submittal Checklist (dated 7.7.2023), Los Angeles Department of Building and Safety. Accessed 2026-10-10.
- 7)ADU Standard Plans Program, City of Pasadena Planning and Community Development Department. Accessed 2026-10-10.
- 8)AB 1332: Preapproval of ADU Plans (Government Code Section 65852.27), San Diego Association of Governments (SANDAG). Accessed 2026-10-10.
- 9)Permit Ready ADU, City of San Ramon, California. Accessed 2026-10-10.
- 10)ADU Ready: Pre-Reviewed Accessory Dwelling Unit Plans, Permit Sonoma, County of Sonoma. Accessed 2026-10-10.
- 11)Pre-Approved Accessory Dwelling Unit (ADU) Program, County of Del Norte, California, Building Inspection. Accessed 2026-10-10.
- 12)Accessory Dwelling Unit (ADU's), City of Hidden Hills, California, Building and Safety and Planning. Accessed 2026-10-10.
- 13)Accessory Dwelling Unit Ordinance and ADU Completeness Checklist, City of Redwood City, Community Development Department. Accessed 2026-10-10.
- 14)Accessory Dwelling Unit Handbook (update): Gov. Code 66310 to 66342, California Department of Housing and Community Development. Accessed 2026-10-10.
- 15)Plans Required to be Designed by Architect or Engineer, City of Milpitas Office of Building Safety. Accessed 2026-10-10.
How these sources were chosen and when the page is reviewed: how we research.