With all the praise and enthusiasm for Accessory Dwelling Units today, you might be surprised by their history. Commonly referred to as in-law units or granny flats by some and infill apartments by affordable housing advocates, they were once highly restricted and outright illegal in many municipalities.

  1. In 2017 a California law (AB68) was enacted that forced local governments to loosen their grip on regulations restricting in-law units, whether they were backyard cottages, converted garage apartments or a living space in a basement, grouped under the umbrella of accessory dwelling units (ADUs).
  2. Units that were once considered illegal can be made legal. Codes and other regulations vary, depending on your location. If your unit was built before 2017, if it meets current state and local codes, you may be able to request amnesty if there are no health or safety violations. If it is an older unit, you may need to invest in structural or other changes that bring it up to code.
  3. Done well, new, or redesigned ADUs can provide much needed affordable housing units, constructed with green building standards in mind, that mutually benefit the property owner and tenant(s). The rents help the property owner pay for the unit and are often reasonable for the tenant compared to renting a conventional apartment or house.
  4. An ADU is a good investment. According to a study done in 2012, entitled “Understanding and Appraising Properties with Accessory Dwelling Units”, published in Appraisal Journal, ADUs can add 51% to your home’s resale value and 25% to 34% of your property’s assessed value.
  5. One-size does not fit all. The size and scope of an ADU project is governed in part by the size of your single-family dwelling. Each municipality retains some control over ADUs, so learning what the codes and guidelines are in your area are still very important.

The state law, AB68 has been aided by further legislation to make it progressively easier to create ADU’s. Each county and the various cities in California, when new laws go into effect require more changes to their regulations.

Staying on top of those changes can prove challenging. Here are a few helpful links to guide your planning.

ADU requirements by City and County:

Once you’ve had an opportunity to review the requirements, you may already be envisioning the kind of structure you’d like to see on your property. If you already have an existing ADU that is not legal, you’ll want to address that by learning what it will take, according to the requirements of the municipality you live within.

Since the ADU requirements are not always simple, you may have more questions about designs and details. If you are just in the imagining stages, this could be a great time to contact a professional who can help you work through the kind of design that would fit best for the size and layout of your current main structure.

If you are older and your children have grown, your questions could revolve around whether it is best to partition rooms for an inner ADU since the rooms are no longer needed by your family. If you are a young couple with little children who truly want to make room for grandparents to move in, you might choose to add on to your current home, or to convert a garage, or build a standalone unit.

Before launching into the creation of an ADU, you may have specific questions about what could work best for you. Please call 415-450-9504 x700 (Marin) or 707-241-4944 (Sonoma) to arrange a complimentary design consultation or press this button to send an email:

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