Frequently Asked Questions

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What does it cost? 


While the price for every project is different, it’s a good idea to budget for ~$400 per square foot.

To get a better estimate, use our calculator tool.

How long does the process take? 


Building an ADU is not only a financial investment but an investment of time as well. Typically, it takes homeowners one to three months to get started and assemble their team. It then takes the project team another one to six months to develop plans, meet with the city, and submit the application. Depending on how many rounds of review are required and how quickly a homeowner and their project team can respond to comments, make changes, and resubmit plans, it will likely take one to six months to get permits. Construction usually takes 6-12 months.

In total, most projects take one to two years to complete.

How am I going to pay for an ADU?

There are five main options available to homeowners to finance their ADU. Many homeowners use a mix of these options. As you’re doing financial planning for your ADU, remember to include the rental income you’ll receive in your calculations. Some lenders will not consider this income when evaluating you for a loan, but it’s important for you to consider it in your calculations.

1) Cash savings or other liquid assets

2) Cash-out refinance

3) Loans from friends or family

4) Home equity loan or home equity line of credit (HELOC)

5) Renovation loans

How will it affect my taxes? 

Adding an ADU will affect your property taxes and the resale value of your home. Your primary house will not be reassessed, and your property taxes will only increase based on the added value of your ADU. If you have low property taxes because you have owned your home for many years, your base assessment will not be affected. The assessor will only review the value of the improvement. For example, if a new home buyer pays would pay $150,000 more for your property because of your ADU, and your property tax rate is 1.1%, your taxes will increase by 1.1% x $150,000 = $1,650 per year. Plus you will continue to pay what you were paying before. 

Junior ADUs or interior conversions have much less (or in some case, no effect) on your taxes.

How do I find an architect and a contractor? 

The Marin Builders Association publishes a free Home Resource Guide and provides a Find Your Contractor directory on their website.

Also consider reaching out to friends, family, and/or neighbors for recommendations. Because contractors are busy, the personal connection can sometimes help.

What do I need to know about becoming a landlord? 

Some folks choose to manage tenants on their own, and others hire a property management firm to take care of everything from collecting rent to maintenance requests.

How much will an ADU increase my property value?

Your ADU will likely add to your home’s value, though the exact amount is difficult to predict because there are few comparable homes to give definitive rules. A very rough rule of thumb provided by Bay Area Realtors is that your new construction ADU will add 100 times the monthly rental value to your home.

For example, if your ADU rents for $1,800, it should add about $180,000 to the value of your home. Other options, such as interior conversion, home sharing, or creating a junior ADU (JADU), will have a smaller impact on value. Home sharing will not increase the assessed value of your home at all, while JADUs will impact the assessed value less than a traditional ADU (or potentially not at all). Since JADUs are a relatively new form of housing, there is currently little data on them. 

How do I get started? 

The first things to figure out are if you’re eligible to build and if you can afford it.