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Pre-Designed ADU Plans & How-To Guide

As a part of the County of Santa Cruz's goal to reduce barriers to building affordable housing, we are excited to offer free, pre-designed ADU plans. Plans come in (3) three sizes and each size is offered in (3) three exterior designs: classic bungalow, coastal Mediterranean, and sleek modern. Permit fees vary depending upon the ADU size and your parcel’s characteristics. 

Plan 1:  425 square foot studio or optional 1-bedroom and 1-bathroom with 76 square foot front porch: Permit fees: approximately $5,000*

Plan 2:  637 square foot 1-bedroom and 1-bathroom with 85 square foot front porch. Permit fees: approximately $6,000*

Plan 3:  998 square foot 2-bedroom and 1-bathroom with 62 square foot front porch. Permit fees: approximately $20,000* + Impact Fees**

* School District and Fire Department Review Fees will be due separately. These vary depending on which school district or fire agency serves your parcel. Fees are paid directly to those agencies prior to permit issuance.
** Impact Fees (e.g., Parks, Child Care) only apply to the 998 square foot design and vary depending upon a parcel's location and the scope of the project.

Important Notes:

(1) These pre-designed ADU plans have been checked for building code compliance and basic health and life safety only.  They must still be reviewed by all relevant departments prior to the issuance of a building permit for construction.  Please see "Step 4: Submit Your Application" for more information. 

(2) Foundations for each ADU are designed as typical slab on grade with monolithic footings per CRC/CBC presumptive soils values. Any project site that does not meet the conditions described will need to seek a soils report for their individual site and develop a custom foundation plan and, in some cases, revised structural calculations. The pre-designed plans may not be modified, so if your project requires a custom foundation plan (or any other modification) the pre-designed plans will not be suitable for your project. You may, however, hire the architecture firm that drafted the plans to customize the plans for your project.

Frequently Asked Questions

Q: Can I modify the pre-designed plans?
A: No. To retain the "pre-designed" status, plans may not be modified. The pre-designed plans are approved only for use in Santa Cruz County. No deviations, alterations, or options beyond those specifically indicated in the plans are allowed without prior approval by the issuing jurisdiction and chief building official. Any unapproved plan modifications may be developed through RRM Design Group and the approving jurisdiction, if required. 

Q: Is a soils report required?
A: No, but a soils report waiver is required. One of the first items you should confirm is whether your site qualifies for a soils report waiver. If your parcel does not qualify for a soils report waiver, then a soils report and custom foundation plan will be required. Because the pre-designed plans may not be modified, projects requiring a custom foundation do not qualify to use the pre-designed plans. The following site and project characteristics disqualify a project from using a soils report waiver:  

  • Project site has expansive soils*;
  • Project site has slopes greater than 20%;
  • Project site has existing cut or fill slopes;
  • Project proposes cut or fill slopes;
  • Project site has mapped or known geologic hazards including liquefaction, landslides, expansive soils, or fault zones;
  • Proposal would not meet slope setbacks detailed in Section 1808.7 of the 2022 California Building Code;
  • Foundations would be on or adjacent to slopes; and
  • There is observed structural distress to onsite foundation elements or slabs on grade.

*How to determine if your property is mapped as having expansive soils: Go to the County's GIS, enter your APN or address, click on the magnifying glass. Once your parcel appears, click on the "Layers" button on the left side. When it opens, scroll down to the Geophysical category, and click on the triangle to the left of "Geophysical" to reveal the layers. Find the "Expansive Soils NRCS" layer. Check the box to turn it on. If your parcel has expansive soils, an orange color will appear on it.

Additional information about soils reports and waivers is available on the Soils Report Requirements & Guidelines webpage.

Q: Will I have to provide any other design work / plan sheets?
A: Yes. At a minimum, you will be required to provide a site plan and stormwater management information. You may need to provide grading and civil engineering sheets depending on how extensive the site preparation will be for your project. Fire sprinkler (if required for your ADU) and roof truss information will be required as a deferred submittal. If your project is served by an Onsite Wasterwater Treatment System (OWTS e.g., a septic system), you may need to develop plans for an upgraded or new system.

Q: I live in the Coastal Zone; will my ADU project require a Coastal Permit?
A: Most ADUs are excluded or exempted from requiring a Coastal Permit. When a Coastal Permit is required, it is typically issued with the building permit. For more information, contact Zoning staff by email or by scheduling an appointment.

Q: Where can I get more information about ADUs?
A: Our ADU website has lots of information, including links to regulations and FAQs. 

 

How-To Guide


Use the ADU Eligibility Tool to determine your parcel’s eligibility for an ADU as well as the maximum size ADU allowed on your property. Be patient; after you enter your address or Assessor's Parcel Number, the tool takes a moment to load your parcel's information.

 

 

  • Confirm your ADU's development standards (e.g., setbacks) with Zoning staff by scheduling an appointment here
  • Confirm with Environmental Planning staff that your property is suitable for an ADU and not encumbered by environmental constraints or resources that require protection. Schedule an appointment here
  • Confirm that your project is eligible for a Soils Report Waiver (see FAQ above).
  • If your property is serviced by an OWTS (septic system), confirm with Environmental Health staff whether an upgraded or new system will be required. An Environmental Health Clearance Building form will be required as part of the application package. Schedule an appointment here
  • If your parcel is served by public water, you will need to contact your local water provider to obtain a “will serve” letter for water hookup.

 

 

Once you select an ADU design and download your pre-designed plans, you can start bringing your ADU vision to reality!

(1) Download the plan set you have selected.

(2) To complete your ADU plan set, you will need to provide a vicinity map and site plan of your parcel. You can hire a designer or architect or you can draw your own site plan. Use the Site Plan checklist on the pre-designed plan set.

Here is a list of submittal requirements that must be included in your application package and the pre-designed ADU plans:

APPLICATION FILE

PLAN SET FILE

  • Property site plan & vicinity map.
  • Photovoltaic system (This can be submitted as a deferred submittal* to be completed prior to final inspections.)
  • Fire sprinklers (This is only required if the main house has fire sprinklers and can be submitted as a deferred submittal.*)
  • Stormwater management design
  • Grading plan and civil plan sheets (if required)

SUPPLEMENTAL DOCUMENT FILE

* Deferred submittals are defined as portions of the design that are not submitted for review at the time of the initial permit application.

 

Submit your ADU application using the County’s online ePlan Review systemIf you have any questions about how to assemble the application package, or how to upload, please schedule an appointment with the Building staff by clicking this link: Appointment Self-Scheduler.

After your submittal is accepted for intake, building counter staff will create the permit application and notify you through the ePlan Review portal when intake fees are due. Once fees are paid, your project will be routed to the applicable reviewing agencies for plan review. 

Are you wondering, “Why do I have to pay for a permit application and review fees if my plans are pre-designed?” Although the ADU plans are pre-designed, each property's characteristics are different. This means that your project may need to be reviewed by multiple agencies. For the two smaller ADU sizes, most review fees will be waived, although reviews will still be applicable. Your project may be reviewed by:

  • Building
  • Zoning
  • Environmental Planning
  • Fire
  • Addressing
  • Transportation
  • Stormwater
  • Sanitation (if on Sewer)
  • Environmental Health (if on OWTS)
  • Housing

You will be notified through the ePlan Review portal once reviews are completed and if there are any corrections to address. If corrections are required, you will need to resubmit your project through the ePlan Review portal.  

After all reviews are complete, you will be notified through the ePlan Review portal of final issuance fees to pay and if any school and fire fee receipts are due. If any additional receipt documents are required, you will be able to upload into the ePlan Review portal as a final APP (this will be your last Application file that was reviewed along with all needed documentation). Once fees are paid and any required receipts are uploaded, your plans and inspection card will be available for download in your project in ePlan Review portal.

Once your Building Permit is issued and plans are uploaded into the ePlan Review portal, construction can begin. 


During the construction process, your ADU will require multiple inspections at different stages in the construction process. Often, reviewers place holds on permits to insure compliance with regulations. These holds are required to be released prior to final inspection and a closed and complete permit.  

Once the ADU is complete and the final inspection takes place, your ADU is ready for occupancy.