Are you a homeowner or real estate investor in Willow Glen, San Jose? If so, you have likely considered building an accessory dwelling unit (ADU). These small homes offer a fantastic way to expand your living space, house family members, or generate rental income. In this post, we will explore Willow Glen’s ADU regulations, costs, and the many benefits these units can bring.
What is an ADU?
An ADU, or Accessory Dwelling Unit, is a secondary housing unit on a residential property. These units can take various forms, including detached buildings, garage conversions, additions, or converted rooms within the primary residence. ADUs are celebrated for their versatility and ability to provide additional living space without the need for new land.
Why ADUs Are Important for Homeowners and Real Estate Investors
ADUs have surged in popularity due to their many advantages. For homeowners, they offer a cost-effective solution to house aging parents, college-age children, or guests. For real estate investors, ADUs represent a significant opportunity to increase property value and generate rental income. The additional unit can be rented out long-term or used as a short-term rental on platforms like Airbnb.
Overview of Willow Glen ADU Regulations
San Jose has seen a rise in ADU permits since 2015, driven by state legislation aimed at easing housing shortages. The city of San Jose has an ADU permit program led by an "ADU Ally" to streamline the application process. This program has been very successful, particularly in District 6, which includes Willow Glen.
San Jose's ADU Permit Program
San Jose launched its ADU permit program in 2019. The program assigns an ADU Ally to guide residents through the application process. The aim is to simplify the construction of ADUs and make it easier for homeowners to comply with local regulations. This has encouraged many residents to submit applications to build ADUs.
Key Legislation Impacting ADUs
Several pieces of state legislation have made it easier to build ADUs in California:
- Senate Bill 1069 prohibits parking requirements if the ADU is within half a mile of public transit.
- Assembly Bill 2406 allows junior accessory dwelling units (JADUs) of no more than 500 square feet within a single-family residence, without additional parking requirements.
- Assembly Bill 2299 relaxes regulations around ADUs, including limiting parking requirements and setback requirements.
Local Regulations in Willow Glen
In Willow Glen, ADUs are permitted in most single-family residential zones (R-1, R-2, and R-M) and planned development (PD) districts. Homeowners must comply with the standards outlined in the Municipal Code, including size, height, and setback requirements.
California's ADU Law as of January 1, 2020
The state of California has introduced legislation to reduce costs and burdens associated with developing ADUs:
- ADU applications must be approved within 60 days without a hearing or discretionary review.
- Cities and counties cannot require the owner to live at the property for ADUs permitted by 2025.
- No impact fees are required for ADUs under 750 square feet.
- ADUs can be developed simultaneously with a primary dwelling under most of the same rules.
Automatic and Ministerial Approval
Certain categories of ADUs are eligible for automatic approval, meaning cities and counties must permit them without applying local development standards. Examples include:
- An ADU or JADU converted from existing space in a home or another structure, provided it has exterior access and sufficient setbacks for fire safety.
- New detached ADUs under 800 square feet, 16 feet in height, with 4-foot side and rear setbacks.
Other ADUs must be approved ministerial, meaning their approval is straightforward and subject to minimal local limits.
Costs of Building an ADU in Willow Glen

The costs of building an ADU can vary widely based on the type and complexity of the project. Here is an overview of the typical costs:
Detached ADUs
Building a detached ADU can range from $110,000 to $300,000. These units are separate structures from the main house and require their own foundation and utilities.
Garage Conversion
Converting an existing garage into an ADU can cost between $110,000 and $290,000. This option is often less expensive than building a new structure because it utilizes existing space and infrastructure.
Above Garage
Building an ADU above an existing garage typically costs between $120,000 and $325,000. This option can be more complex due to structural requirements and the need to integrate the unit with the existing garage.
Home Addition
Adding an ADU to the existing home can cost between $85,000 and $225,000. This involves expanding the current living space to include the new unit.
Room Conversion
Converting a room within the existing home into an ADU is the most affordable option, costing between $30,000 and $80,000. This option requires minimal construction and utilizes existing infrastructure.
Benefits of ADUs
ADUs offer numerous benefits for both homeowners and real estate investors:
Increased Property Value
ADUs can significantly increase the value of a property. The additional living space and potential rental income make homes with ADUs more attractive to buyers.
Rental Income
ADUs provide an excellent source of rental income. Homeowners can rent out the units to long-term tenants or use them as short-term rentals. This additional income can help cover mortgage payments and other expenses.
Flexibility and Versatility
ADUs are incredibly versatile. They can serve as guest houses, home offices, or living spaces for family members. This flexibility makes them a valuable addition to any property.
How to Get Started with Building an ADU
Building an ADU involves several steps. Here's a brief overview of the process:
Research and Planning
Start by researching local regulations and understanding what is allowed in your area. Consider how the ADU will be used and what type of unit will best meet your needs.
Permitting Process
Submit an application to your local planning department. The application will include detailed plans for the ADU, including its size, location, and design. Work with your ADU Ally to ensure your application meets all requirements.
Construction
Once your application is approved, you can begin construction. Work with a reputable contractor to ensure the project is completed on time and within budget.
Conclusion
Building an ADU in Willow Glen can be a rewarding investment for homeowners and real estate investors alike. These units offer increased property value, rental income, and flexibility. With the support of local regulations and state legislation, building an ADU has never been easier.
If you're considering building an ADU, now is the perfect time to get started. Contact your local planning department or an ADU Ally to learn more about the process and begin your application.
By understanding the regulations, costs, and benefits of ADUs, you can make informed decisions and take full advantage of this valuable opportunity. Whether you're looking to house family members, generate rental income, or simply add more space to your home, an ADU is a smart and practical solution.
If you'd like personalized guidance and support, consider scheduling a consultation with our ADU experts. who specializes in ADU construction and planning. They can help you navigate the process and ensure your project is a success.