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SB9 vs ADU


California has been facing a housing crisis for several years, with rising home prices and rents making it difficult for many individuals and families to find affordable housing. As a result, policymakers have been exploring various options to increase the housing supply, including SB9 and ADUs.

SB9, or Senate Bill 9, is a recently passed bill that allows homeowners to build two units on their property, such as a duplex or two detached homes, as long as the property is zoned for residential use and meets a certain size and other requirements. Conversely, ADUs, also known as accessory dwelling units, are diminutive residential structures that can be erected on the identical property as an established single-family abode, frequently located in the rear yard or garage.

In this article, we will explore the key differences between SB9 and ADUs, as well as the pros and cons of each option. We will also provide some considerations for homeowners and municipalities when deciding which option to choose.

SB9 vs ADU: The Key Differences

The key differences between SB9 and ADUs can be listed as follows:


  1. Size and Configuration: SB9 allows for larger units such as duplexes or two detached homes, while ADUs are generally limited to a maximum size of 1,200 square feet or less.
  2. Zoning Requirements: SB9 requires that the property is zoned for residential use, while ADUs may be allowed in other zones such as commercial or mixed-use. However, ADUs often have more specific requirements related to setbacks, height limits, and other design considerations.
  3. Permitting Process: SB9 requires a ministerial review process, which means that the local government must approve the project as long as it meets certain requirements. ADUs, on the other hand, require a discretionary review process, which means that the local government has more discretion in approving the project and may require additional design or environmental review.
  4. Setbacks, Open Space, and Parking: SB9 has specific requirements for setbacks, open space, and parking, which can vary depending on the property’s location and zoning.
  5. Cost: The cost of SB9 and ADUs can vary depending on the size, design, and location of the units. SB9 may be more expensive due to its larger size and more complex design, while ADUs may be less expensive due to their smaller size and simpler design.

SB9 Pros and Cons 


SB9 has several potential benefits for homeowners and communities. Here are some potential pros of SB9:

Here are some cons of SB9:

It’s important to note that many of these potential pros and cons are speculative, as the bill has not yet been implemented and its impact is not yet known.

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 ADU Pros and Cons

ADUs also has several potential benefits for homeowners and communities. Here are some pros of ADUs:

Here are some pros of ADUs:

How to choose between SB9 and ADUs?

When considering whether to build an SB9 unit or an ADU, homeowners should take several factors into account:


Check with your local zoning laws to see if ADUs are allowed in your area. Some cities have specific requirements, such as size limitations or parking requirements.


ADUs can be expensive to build, so consider your budget before making a decision. SB9 can be a more affordable option, as it allows for two residential units on a single-family lot.

Size of property

If you have a larger property, an ADU might be a better option as it can be built separately from your primary residence. However, if you have a smaller lot, an SB9 might be the only option available.

Rental income

If you’re looking to generate rental income, an ADU may be a better option as it can be rented out as a separate unit.


Consider how much privacy you need. An ADU provides more privacy as it’s a separate dwelling, whereas SB9 means you’ll share a property with tenants.


Maintenance of an ADU can be more expensive as it’s a separate structure, while an SB9 is likely to share a lot of maintenance costs with the main dwelling.

Resale value

An ADU can increase the value of your property, but an SB9 may have a limited appeal to buyers who don’t want to share their property with tenants.


Consider the intended purpose of the additional unit. An ADU can serve as a home office, guesthouse, or rental property.


ADUs require separate construction, while SB9 can utilize existing structures, like a garage or basement, to convert into an additional unit.


SB9 and ADUs are two options for increasing the housing supply in California. While SB9 allows for larger and more complex housing units, ADUs are smaller and less expensive to build. Ultimately, both SB9 and ADUs can play an important role in addressing California’s housing crisis and promoting more sustainable and livable communities.

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