Completed ADU

What is an ADU?

ADU stands for Accessory Dwelling Unit. It is an additional, self contained housing unit that is secondary to the main residence. ADU’s are sometimes referred to as “Granny Units” or “Mother-In-Law units” since many ADU’s were initially constructed to provide housing for family members. They can take many forms. In some cases, an ADU can be attached as an addition to the house, or as a second story over a garage. The garage itself may be converted to an ADU or the ADU may occupy a basement. An ADU can be a section of the main house that is separated from the main living space, or an ADU can be a stand-alone unit like a small house or cottage. The City of Santa Cruz only requires that an ADU have a kitchen, bathroom, and place to sleep.

How is an ADU different than a duplex?

To legally qualify as an ADU, the owner must reside in either the main house or the ADU. An ADU is also limited in size and is usually smaller than the main residence.


Why would I want to build an ADU?

An ADU can provide a separate living space for family, a home office, or a rental, among many other uses. Many people in the city have a hard time making their mortgage due to the high cost of living in Santa Cruz. Converting a garage or building a new ADU, and then renting it, is one way to make added income while adding value to your property at the same time. If you don't have the savings in the bank, the project can be financed with a loan, and then rent can easily cover the new monthly payments.

Here is an example of how an ADU can make you money:

You have a 480 sf garage that you would like to convert into an ADU. We go through the design and bid process and agree to build the ADU for, say, $125,000. You don't want to dip into all of your savings, so you decide to pay $50,000 out of pocket, and get a loan from a bank for the rest. Interest rates vary over the years and banks offer many types of loans, but for this example, let’s assume you get a $75,000 HELOC, 20 year loan, at a fixed 6%. This works out to be a monthly payment of $537. We build the ADU and then you rent it for $1,800 per month, which is an average rent for this size ADU. If we assume there is a small increase in property tax and insurance of $225/month, you have a net gain of $1,038 per month! At the same time, your property value has risen by at least $125,000.

How large can my ADU be?

In the City of Santa Cruz- you can build up to 10% of your lot size with a maximum allowable ADU of 1200sf.

In the County of Santa Cruz- they allow up to 640sf within the urban services line, where sewer and water utilities are provided. Outside of the urban services line, ADU’s are allowed up to 1200sf depending on your parcel size.

Please contact us to find out more!

How do I find out the size of my lot?

Visit the County Assessor’s Office or call the City Planning Department at: 831.420.5100 


How much will it cost?

The cost to build an ADU varies widely. A garage conversion can be relatively inexpensive, while a custom, stand alone ADU, or ADU on top of a garage, is more expensive. Here is a breakdown of some basic costs.

Soft Costs:

  • $10,000-25,000 for Planning and Building Department fees, depending on the size of the ADU and if it is a conversion or new ADU

  • $5,000-15,000 for water, sewer, and fire sprinkler connection(sprinklers only needed if main house has sprinklers), depends on whether the existing services can be shared or if new services need to be tapped in at the street. Add more if you are in the Soquel Creek Water District

  • $2,000-8,000 for PG&E electric hookup/panel upgrade, depending on if you have a 200 amp panel, or if a new service is required, and how far gas line needs to run from shared meter(or go all electric and add solar!)

  • $10,000-30,000 for architectural plans, structural engineering, title 24 energy modeling, and possible soils report. Garage conversions may not require very large plan sets, while stand alone ADU’s require structural engineering and a soils report.

ADU in Santa Cruz

Building Costs:

  • $60,000-120,000 for garage conversions, depending on the condition of the existing garage, and if you are adding on additional space

  • $150,000-400,000 for stand alone units, depending on size, site, accessibility, finishes, and building department requirements. $400/sf is a good ballpark for building cost. For larger ADU’s over 800sf, the square foot cost may come down because of the economy of scale. 

* A note on cost: If you have a tight budget, a garage conversion is usually the most affordable way to build an ADU, and often has the best return on investment, if used as a rental. For new stand alone ADU’s, costs can be kept to a minimum by doing a simple design, and using affordable but durable finishes. During the planning process, we can advise on how to keep costs down and quality up!

 How long will it take to design, permit, and build?

The design phase is usually about 3 months, depending on complexity. Permitting is usually another 3 months. Construction usually takes 5 months for garage conversions, 7 months for smaller stand alone ADU’s, and up to 1 year for large ADU’s. It may take more or less time depending on the complexity of the project and the time of year the process is started.

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How can I finance building an ADU?

There are many ways that people finance constructions costs. We recommend talking with your current mortgage lender about credit available to you. 

Who can live in the ADU?

Anyone can live in your ADU. Or you can use it as an office. The City of Santa Cruz does require that the owner either live in the ADU or the primary dwelling on the property. The other dwelling can be rented.

 Can I rent the ADU?

You can rent the ADU, or live in the ADU and rent the primary residence. In no case can an ADU qualify as a legal short term vacation rental.

How much can I rent the ADU for?

The University of Santa Cruz Housing Services statistics for 2018 have studio apartments in the City of Santa Cruz renting for an average of $1,428, and one bedroom units renting for $1,995. The actual rental cost for your unit will likely be higher since it will be nice and new, but rents can vary.

I don’t live in the City of Santa Cruz.

The County of Santa Cruz has a ADU plan and an informative website to help you out.

Can I see an ADU that Santa Cruz Green Builders has built?

Yes. Call, email us, or visit the contact page and we will arrange for a visit.

Where should I start?

The first step is to see if you can build an ADU on your property.

Visit our Do I Qualify page to see if an ADU is right for you.

Then the next step is to visit the County of Santa Cruz Planning Department to see if there are any special restrictions that would keep you from building- be sure to have your property address and/or APN# with you. At this point you can also call us and we can do this step for you. We are happy to come out to your property to look at your lot configuration, setbacks, and other buildings, to see if your lot can accommodate an ADU.

Once your property is deemed acceptable for an ADU, it is time to do the design. You can use one of the City’s pre approved ADU designs (which need some updates and engineering) or you can start from scratch and create your own design.We now offer in house design services to streamline your project or you can bring in your own architect or designer. Regardless of who you use, it is important that the property owner, builder and designer all work together on the design. This ensures an efficient building process that is kept on budget and results in a much better finished product. 

How do I get in touch with Santa Cruz Green Builders?

Call us at 831.566.4485 or send an email to


More info:  Do I Qualify?    /    Financing    /    Links

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