ADU Regulations in San Jose: What Homeowners Need to Know

San Jose is a great place to live—but it’s also one of the most expensive. Many homeowners are looking for ways to make better use of their property. One smart option is to build an Accessory Dwelling Unit, or ADU. These small homes can be used for renting, hosting family, or just adding extra living space.

But before you start building, it’s important to understand the city’s rules. San Jose has specific laws about where and how ADUs can be built. This article will explain what ADUs are, why people build them, and the steps you need to take to stay within city guidelines.

🔑 Key Takeaways

1. ADUs Are Legal and Encouraged in San Jose
   You can build one ADU and one Junior ADU (JADU) on most residential lots, thanks to California laws and San Jose’s updated regulations.
   
2. Multiple ADU Types Are Allowed
   San Jose permits detached ADUs, attached ADUs, garage conversions, and JADUs. Each type has its own size and placement rules.
   
3. No Minimum Lot Size Required
   Most single-family and multi-family homes in San Jose qualify for ADU construction regardless of lot size.
   
4. Size Limits Depend on the Type of ADU
   
   • Detached ADUs: Up to 1,200 sq. ft.
     
   • Attached ADUs: Up to 50% of the main home’s size
     
   • JADUs: Up to 500 sq. ft.
     
5. Setback and Height Rules Apply
   Detached ADUs must be at least 4 feet from side and rear property lines. Height is usually limited to 16 feet, with some exceptions.
   
6. Extra Parking May Not Be Required
   Many ADUs are exempt from parking requirements, especially those near public transit or converted from garages.
   
7. Permitting Is Required
   All ADUs need city approval through a building permit. The process takes several months and includes plan review and inspections.
   
8. ADUs Must Follow Building and Energy Codes
   Units must meet standards for safety, utilities, solar, and energy efficiency—just like any other home.
   
9. Cost Ranges from $150,000 to $300,000+
   ADU costs depend on size, design, and site conditions. Financing is available through options like Enhancify.
   
10. Common Mistakes Can Be Avoided with the Right Help
    Working with a knowledgeable local contractor like Elevated Edge Construction helps you avoid delays, redesigns, and added costs.
    
11. ADUs Add Flexibility and Long-Term Value
    Whether for rental income, family housing, or increased resale value, ADUs offer a smart, lasting solution for San Jose homeowners.
    

What Is an ADU?

An ADU is a smaller, second home built on the same lot as your main house. It has everything someone needs to live independently, including a kitchen, bathroom, and sleeping area.

There are four main types of ADUs:

• Detached ADU – A separate building in your yard, like a backyard cottage
  
• Attached ADU – A unit that is connected to your main home but has its own entrance
  
• Garage Conversion – Turning an existing garage into a livable space
  
• Junior ADU (JADU) – A small space inside your home (up to 500 sq. ft.), often using an existing bedroom or part of the garage
  

Example: A homeowner in Cambrian Park has an unused garage. Instead of letting it sit empty, they turn it into a small rental studio.

Why San Jose Homeowners Are Building ADUs

Homes in San Jose are expensive. The average house costs around $1.5 million, and rent is also very high. Because of this, many families are using ADUs to solve everyday problems.

Here are some reasons people build them:

• To earn extra money by renting the space
  
• To give family members—like grandparents or grown children—a place to live nearby
  
• To avoid moving when more space is needed
  
• To increase property value over time
  

Example: A couple in Willow Glen wants their aging parents to live close by. Instead of paying for assisted living, they build a small ADU in the backyard. Now, their parents have privacy, comfort, and support just steps away.

The Basic Rules for Building an ADU in San Jose

San Jose follows California’s laws, which are designed to make building ADUs easier. Still, the city has its own rules too. Here are some of the most important:

• You can usually build one ADU and one JADU on the same lot
  
• There’s no minimum lot size
  
• A detached ADU can be up to 1,200 square feet
  
• An attached ADU can be 50% of your main home’s size
  
• A JADU must be 500 square feet or less and located inside your main house
  

Example: A homeowner in the Rose Garden neighborhood has a 2,000 sq. ft. home. They’re allowed to build a 1,000 sq. ft. attached ADU and a 500 sq. ft. JADU—all within the law.

Zoning and Setback Rules

Even if your property qualifies for an ADU, you still need to build it in the right place. This is where zoning and setbacks come in.

Here’s what you need to know:

• Detached ADUs must be at least 4 feet from the back and sides of your property
  
• Conversions of existing garages may not need extra space
  
• Most ADUs can be up to 16 feet tall, but some may go higher if built above a garage
  
• You must follow your area’s lot coverage rules, which limit how much of your property can be built on
  

Example: A family in Almaden Valley wants a backyard unit. They adjust the layout to meet the 4-foot setback rule, so it fits within city guidelines.

How Big Can an ADU Be?

The size of your ADU depends on the type and your existing home:

• Detached ADU: Up to 1,200 sq. ft.
  
• Attached ADU: Up to 50% of the main home’s floor area
  
• JADU: No more than 500 sq. ft.
  

You also need to follow some basic design rules:

• The ADU must match the style and look of your main home
  
• Rooms must meet certain size and ceiling height requirements
  
• The unit must have its own entrance, kitchen, and bathroom
  

Example: A homeowner with a 2,000 sq. ft. house can build an attached ADU that’s up to 1,000 sq. ft. This is enough for a comfortable one- or two-bedroom unit.

Parking Rules for ADUs

One big concern is parking. But the good news is that extra parking is often not required.

You usually don’t need to add parking if:

• Your home is within half a mile of public transit
  
• You’re converting a garage or basement
  
• You live in a historic neighborhood or an area with street parking restrictions
  

When parking is required, tandem parking (one car parked behind another) is allowed.

Example: A homeowner near a VTA station converts their garage into an ADU. Since they’re close to transit, no new parking is required.

How to Get a Permit

Before building your ADU, you must get permission from the city. This is called a building permit. It makes sure your project is safe and legal.

The steps are:

1. Plan your ADU (size, layout, and location)
   
2. Submit your plans to the city for review
   
3. Make changes if the city requests any
   
4. Get your permit
   
5. Start building
   
6. Pass inspections during and after construction
   
7. Get final approval
   

The entire process usually takes 6 to 9 months. Working with a contractor who knows San Jose rules can help avoid delays.

Construction and Utility Services

Your ADU will need water, electricity, heating, and plumbing—just like your main home. Here’s what to consider:

• You can use the same utility connections as your main home or install separate meters
  
• Solar panels are required for all new detached ADUs
  
• Fire sprinklers may be required, depending on where the unit is built
  
• San Jose also requires energy-saving features, like insulation, good windows, and efficient appliances
  

Example: A homeowner finds out their electrical panel isn’t strong enough to power both the main home and the ADU. They upgrade it to 200 amps to meet the needs of both units.

How Much Does an ADU Cost?

ADUs can be a big investment. In San Jose, they usually cost between $150,000 and $300,000, depending on size, design, and materials.

You don’t have to pay all at once. Here are ways to pay for an ADU:

• Home equity loan
  
• Cash-out refinance
  
• Construction loan
  
• Enhancify financing through Elevated Edge Construction (monthly payments available)
  

Example: A homeowner wants to build a $225,000 ADU but doesn’t want to use all their savings. They use Enhancify financing to pay in smaller, more manageable payments over time.

Common Mistakes to Avoid

Here are a few mistakes that can slow down your project or cost you more money:

• Not checking city rules first
  
• Not budgeting for unexpected costs
  
• Working with a contractor who doesn’t know San Jose laws
  
• Creating a design that’s too big or doesn’t meet code
  

Example: A homeowner designs a loft in their ADU but later finds out the ceiling is too low to meet code. They have to change the plans, which adds more time and cost.

How Elevated Edge Construction Can Help

Elevated Edge Construction is based in San Jose and has over 15 years of experience. We know the local rules, understand the permit process, and build high-quality ADUs that last.

Here’s what we provide:

• Help with planning and design
  
• Permit-ready drawings
  
• Project management from start to finish
  
• Expert construction crews
  
• Flexible financing through Enhancify
  

We’ve helped homeowners across San Jose, Campbell, Los Gatos, Saratoga, and the East Bay turn unused space into beautiful, livable units.

Conclusion

Building an ADU is a great way to add value, create space, and make your property more useful. Whether you want to host family, rent out a unit, or just plan for the future, an ADU gives you new options without having to move.

But the process takes planning, knowledge of the rules, and the right team to guide you. That’s where we come in.

Schedule a free consultation with Elevated Edge Construction today. We’ll help you plan, permit, and build your ADU the right way—from the first idea to the final inspection.

Frequently Asked Questions (FAQs)

This article has been a collaboration between Elevated Edge Construction and OpenAI’s ChatGPT. Created on March 27, 2025, it combines AI-generated draft material with Elevated Edge’s expert revision and oversight, ensuring accuracy and relevance while addressing any AI limitations.

George Shafazand CEO

With over 17 years in the construction industry, George Shafazand has extensive experience in construction management and real estate development. He has successfully led multi-residential, commercial, and retail projects from planning to completion. He specializes in construction administration, project management, land development, and contract negotiations to ensure projects are delivered on time and within budget. As a Project Manager and Owner’s Representative for over a decade, George has overseen feasibility analysis, entitlements, funding, contract negotiations, and construction execution. He holds a Bachelor's degree in Industrial Engineering, multiple property management certifications, and is an active member of the California Bureau of Real Estate.

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