SB9 vs ADU

Posted in   Uncategorized   on  April 13, 2023 by  admin0

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:

  • Increased housing supply: SB9 could potentially lead to the creation of more housing units in areas with high demand, which could help alleviate the state’s housing shortage and make housing more affordable for residents.
  • Improved transportation: By encouraging development near transit hubs, SB9 could make it easier for people to use public transportation and reduce reliance on cars.
  • Economic benefits: Increased development could stimulate the economy by creating jobs in construction and related industries.
  • More vibrant neighborhoods: Higher density could lead to more diverse and active neighborhoods, with more shops, restaurants, and community spaces.

Here are some cons of SB9:

  • Negative impact on neighborhoods: Some residents may be concerned that increased density and taller buildings could negatively impact the character of their neighborhood, such as by blocking views or changing the feel of the area.
  • Increased traffic: More people living in an area could lead to increased traffic and congestion, especially if infrastructure improvements are not made to accommodate the new residents.
  • Reduced parking availability: Higher-density development may require more shared parking arrangements, which could lead to reduced parking available for residents and visitors.
  • Environmental concerns: Increased development could lead to more pollution and greenhouse gas emissions, especially if transportation infrastructure is not improved to accommodate the increased density.

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.

 ADU Pros and Cons

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

  • Elevated Real Estate Worth: By constructing an Accessory Dwelling Unit, you can boost the value of your property by increasing its livable area, which could also result in supplementary revenue from rent. Additional Revenue Stream: Renting out your ADU is an excellent method to generate additional income. This additional income can assist property owners in paying their mortgages or financing other expenses.
  • Additional Revenue Stream: Renting out your ADU is an excellent method to generate additional income. This additional income can assist property owners in paying their mortgages or financing other expenses.
  • Multigenerational Living: ADUs can provide an alternative to senior living facilities or assisted living for elderly parents or family members, allowing them to live close by and maintain their independence.
  • Housing Affordability: ADUs can be used to address housing affordability issues by providing an additional unit on an existing property.

Here are some pros of ADUs:

  • Cost: The cost of building an ADU can be significant, depending on the size, design, and location. The cost may also vary based on the materials used and the type of construction.
  • Zoning Laws: Some cities or municipalities have strict zoning laws and regulations regarding the construction of ADUs, which can make the process challenging.
  • Maintenance: Maintaining two separate living units can be challenging, especially if you are renting out the ADU.
  • Neighborhood Concerns: Some neighbors may be concerned about the impact an ADU may have on parking, traffic, or property values in the neighborhood.
  • Overall, ADUs can be a beneficial addition to a property, but it is important to weigh the pros and cons carefully before deciding to build one.

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:

  • Zoning

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.

  • Budget

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.

  • Privacy

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

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.

  • Purpose

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

  • Construction

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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