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Accessory Dwelling Units (ADUs) FAQs

Learn the answers to the most frequently asked questions about Accessory Dwelling Units, which are small houses (i.e. “casitas”) added to properties that already have a main house.

Can I have an ADU on my property?

ADUs are allowed in these Residential zone districts:

  • R-A
  • R-1
  • R-T
  • R-ML

Check the zoning on your property on this IDO zoning map by putting your address in the search bar at the top.

Is an ADU feasible on my property?

There are several regulations that limit the size of ADUs that you should consider in deciding whether an ADU is feasible on your property.

  1. ADUs cannot take up more than 25% of the combined area of the side and rear yard of the property.

You may need a survey to calculate the square footage based on your setbacks and the placement of your house. If you have a mortgage, you may have a survey in your paperwork.

  1. ADUs cannot be more than 750 square feet, even if the calculation above would allow a larger square footage.
  2. ADUs must be set back 5 feet from either the rear or one of the sides of the property.
  3. ADUs must be at least 10 feet from existing structures (e.g. the main house or a house on the neighboring property) OR have fire-rated construction (which may be more expensive to construct).

How can I get permission to build an ADU?

  • ADUs are reviewed / decided by City Planning Department staff.
  • The required application is a building permit with a full set of construction drawings and a scaled site plan that shows property lines and existing structures.

How can I finance an ADU?

ADUs are typically financed by conventional banks through a Home Equity Loan, either through refinancing an existing mortgage or using home equity as collateral for a second mortgage.

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