San Jose ADU Requirements 2020: What You Need to Know About Building an ADU

During times of crisis, keeping your loved ones close is more important than ever. And within the last several years, California has weathered several crises–first the affordable housing crisis, and now the coronavirus pandemic.

But when the going gets tough, it’s important to remember that we’re all in this together. And when it comes to your family, you shouldn’t have to settle for anything less than the best option.

If you’re trying to create a home that can truly help your family support each other, an accessory dwelling unit (ADU) is a fantastic investment. But while San Jose has simplified the process for homeowners, navigating the requirements can still be a bit of a headache for those unfamiliar with building requirements.

Here’s a closer look at everything you need to know about San Jose ADU requirements 2020.

The Importance of ADUs in 2020

In these trying times, keeping your family close is more important than ever before.

California homeowners and their loved ones were already facing dire straits prior to 2020 thanks to the affordable housing crisis–especially if you live in San Jose. As of February, described buying a house in San Jose as an almost Herculean feat. It’s one of the most difficult places to buy a home in the U.S., with just four active listings per 1,000 households.

Then, the coronavirus pandemic hit.

Thanks to the housing crisis, finding a property you could afford that also happened to be near your job was a nightmare. Even if you earned a high salary compared to the rest of the country, a huge portion of your paycheck was eaten up by housing.

Now, with the Silicon Valley area bracing for the economic impact of the pandemic, many homeowners and their loved ones are worried about affording their homes in the absence of a steady paycheck.

This is when ADUs are more important than ever as a chance for your family to come together, stay together, and support each other.

Smart Investments in Long-Term Elder Care

Those 60 and older, especially those with pre-existing medical conditions, are at an unusually high risk of severe or deadly coronavirus infections. Tragically, this means that senior care facilities are a dangerous place during the pandemic. In fact, nearly half of California’s reported deaths have occurred among assisted living patients and staff.

Before the pandemic, elder care homes were a resource for families who needed help to provide care to their elderly relatives. Now, elder care homes pose a real danger to your loved ones.

ADUs offer a smarter (and safer) alternative for those who need elder care.

With an ADU, you can create exactly the space your loved one needs. Instead of trying to find a space that meets all of their accommodation needs, such as wheelchair accessibility, senior-friendly showers, or lack of stairs, you can build that space for your loved one.

That way, you’ll get more than just a functional space–you’ll get a space that can grow with your loved one for many years to come.

Better still, ADUs are a more effective way to keep the whole family in quarantine while keeping everyone safe from infection. Your loved one can avoid the hazards attached to elder care facilities, but they can still receive the support they need when at-home visits are non-existent. And for caregivers, it’s that much easier to drop in and provide a helping hand.

Keeping Family Close During COVID-19

More than anything, though, ADUs are a way to keep the family closer during a time of crisis.

The pandemic is especially frightening for seniors, who are at the greatest risk of severe or lethal infections. They’re also more likely than the rest of the population to be isolated, especially if they happen not to live near their relatives (and in California, living on a limited income means seniors may be forced to live a significant distance from their loved ones).

This poses a serious practical concern for seniors who are on their own. It may not be safe for them to travel outside their homes, especially if they happen to have a chronic health condition or are immune-compromised. But they also need to go out for basic necessities.

Using an ADU to house your loved ones is a way to help your vulnerable loved ones stay safe and healthy. By having them stay in an ADU with you, they now have access to the whole family, even if they quarantine separately from the rest of the household.

That way, you can run errands they need–picking up prescriptions, buying groceries–and deliver them without contact. You can also provide each other the emotional support you need to stay strong and keep your hopes up, which is just as important for your wellbeing.

The Care Your Family Deserves

Above all, ADUs provide you the opportunity to give the care that your loved ones deserve, during the pandemic and once the pandemic is finally over.

As the old adage goes, it takes a village. That applies to raising children and caring for your loved ones in equal measure. Families are only as strong as the support they give each other. Like many families, in California and all across the country, you’re doing the best you can with what you have. Through thick and thin, the one thing you can rely on is each other.

ADUs allow you to provide your family with a home–not just a roof over their heads, but a place where they can stay safe, no matter what surprises life has in store. They give families the chance to take care of each other, no matter what that means for your family.

And when it comes to the people who matter most, that’s a priceless investment.

San Jose ADU Requirements 2020

We’re here to help your family build the ADU that you need. Not as a monetary investment, but rather as an investment in the people who matter most in your life.

We also know that making heads or tails of San Jose’s ADU requirements is not for the faint of heart, if only because most homeowners don’t know enough about regular housing laws to be able to make sense of unique ADU requirements.

That’s where we come in.

In light of the recent crises, we’re here to help homeowners like you understand what you need to know to build an ADU for your loved ones.

ADU Universal Checklist

When you’re starting the process of building an ADU, the single best resource at your disposal is the ADU Universal Checklist provided by the City of San Jose.

The checklist was explicitly designed by the city to help homeowners avoid headaches. With the checklist in hand, homeowners can avoid many of the costly and tiresome headaches associated with changing their ADU plans once they’ve already begun the permitting process. It will also help shorten the duration of your project from start to finish.

The list covers everything from qualifying to zoning to building requirements. If there’s anything you need to know about your ADU, it’s likely to be found in the checklist. So save a copy, print it out, and keep it close by throughout the process.

Zoning and Permitting Requirements

With that in mind, let’s talk about zoning and permitting requirements, which are the first bridge to cross in the process of building an ADU.

There are four residential zones in San Jose which are allowed ADUs:

  1. R-1 (single-unit residential, the most common type of zoning in residential neighborhoods)
  2. R-2 (two-unit residential)
  3. R-M (multiple-unit residential)
  4. PD (planned development)

To check your property’s zoning, visit and enter the property address or Assessor’s Parcel Number (APN). You can also check the San Jose Zoning Map and search your address.

Your property must fall under one of those four zoning designations, or must meet one of the following General Plan designations:

  • Residential neighborhood, mixed-use neighborhood, or mixed-use commercial
  • Urban residential, transit residential, or rural residential
  • Downtown or urban village

If your property does not meet one of the above requirements, an ADU is not allowed.

If it does meet one of the above requirements and you have a single-family property, one ADU may be allowed (subject to some standards).

If your property meets one of the above requirements and you have a duplex or multifamily property, two detached ADUs may be allowed. Duplexes may also allow one attached ADU.

Property Designations

The Universal Checklist also outlines four property designations to be careful of:

  1. Easements
  2. Historic designations
  3. Geohazard zones
  4. Flood zones

Your property will have additional requirements if it has a designated easement. The most accurate way to check is by obtaining a copy of the title report that came with the purchase of your home.

If your property has a historic designation, you may still be allowed to build an ADU, but simplified design standards will apply in order to comply with your property’s historic designation.

If your property is in a designated “geohazard” or “landslide” zone, you will need a Geologic Hazard Clearance in addition to your other permits.

If your property is in Flood Zones A, AE, AH, or AO, your plans will have to comply with the appropriate Flood Zone design requirements, which are detailed in Bulletin #211 – ADU Plan Requirements.

Not sure how your property is designated? The best place to start is by checking your zoning. If you’re not sure where to look or what a designation means for your plans, speak with an ADU builder or a City Planner to clarify any questions and ensure your plans are up to code.

Development Standards

Depending on the type of ADU you intend to build and your unique property type, you will also have to navigate additional development standards.


Single-family units may be allowed attached ADUs or detached ADUs. Attached ADUs must share a wall with the main residence, or share a roof structure and be separated by no more than 10 feet. If that ADU is in the front yard, the front door cannot be on the same street-facing facade as that of the primary residence, with some exceptions.

Detached ADUs for single-family units must be either in the backyard or 45 feet from the front of the property line, with a minimum six-foot separation from the main unit. A converted detached garage or detached building may be used for this purpose, or the ADU may be attached to the detached garage or detached building.

Duplex or Multifamily

For duplex or multifamily units, attached ADUs may only be constructed by converting pre-existing non-livable space in the primary unit, such as:

  • Attic
  • Garage
  • Basement
  • Storage room
  • Boiler room
  • Passageway

Detached ADUs follow the same rules as single-family units: they must be either in the backyard or 45 feet away from the front of the property line, with a minimum six-foot separation from the main unit. You may convert a detached garage or detached building to a detached ADU, or attach the ADU to the detached garage or detached building.

Sizing and Height Restrictions

Even if your lot is approved for an ADU, you will have to account for certain sizing and height restrictions in your plans. The plan must be within the maximum limits shown in the ADU Universal Checklist and account for the Rear Yard Coverage Limitation.

The Rear Yard Coverage Limitation states that the cumulative coverage of the rear yard by structures, including the ADU, accessory buildings, gazebos, sheds, etc., may not exceed 40% of the yard or 800 square feet, whichever is greater.

Here are the maximum limits, split by single-family units versus duplexes and multifamily units. Keep in mind that the square footage of all livable areas connected by a door counts toward your allowable square footage.

Single-Family Units

For single-family lots of up to 9,000 square feet, a detached ADU cannot be larger than 1,000 square feet. An attached ADU can be up to 800 square feet or up to 50% of the primary residence square footage without exceeding 1,000 square feet.

For single family lots 9,000 square feet and up, detached ADUs cannot be larger than 1,200 square feet. Attached ADUs can be up to 800 square feet or up to 50% of the primary residence square footage without exceeding 1,000 square feet.

As for height, attached ADUs have the same height limits as the primary residence. One-story detached ADUs cannot exceed 18 feet in height, while two-story detached ADUs cannot exceed 24 feet.

Duplex or Multifamily Units

Fortunately, the sizing for duplex and multifamily units is simpler to navigate.

Regardless of lot size, detached ADUs and attached ADUs both have an 800 square foot maximum.

Because attached ADUs must be created by converting pre-existing non-livable space, the attached ADU must maintain the existing height of that space. Detached ADUs have a 16-foot maximum.


Think you’ve found the perfect spot for your ADU? If you haven’t thought about setback requirements, think again.

For single-family units, attached ADUs have the same setback requirements as the primary residence.

Detached ADUs on single-family lots must be a minimum of 45 feet from the front property line. You may be able to have three-foot setbacks in the rear, but these will be subject to fire mitigation standards.

However, if you have a new ADU with more than 40% rear lot coverage or a second-story ADU, the ADU must be set back at least four feet from the rear and side property lines.

For duplexes and multifamily units, detached ADUs must be in the rear yard or 45 feet from the front property line. There is a minimum four-foot setback for rear and side setbacks, with up to one-foot projection allowed for eaves. A second-story ADU must be set back four feet from the rear and side property lines. Attached ADUs keep their original setback requirements.

However, if you have a corner lot, you are required to have a 10-foot setback, regardless of what type of property it is.

If you have a lot of at least half an acre or more on a riparian corridor, you have a minimum 100-foot setback.

Oh, and if you have any decks, second-story balconies, and unenclosed landings, you have a minimum 15-foot setback from the rear and side property lines.


We’ve spent a lot of time talking about the overall ADU. But under San Jose building requirements, the actual internal contents of the ADU are also regulated and will affect whether or not your plan is approved.

Take sleeping areas, for example. All ADUs, regardless of size or type, are allowed up to two bedrooms, with a maximum bedroom size of 400 square feet. Keep in mind, however, that the ADU must be a fully functional living space, with a kitchen, bathroom, and storage.

The kitchen in detached and attached ADUs must have:

  • Permanent cooking facilities (i.e. stove and oven)
  • Sink
  • Preparation counter
  • Storage
  • Cabinets

The bathroom must have a sink, toilet, and shower and/or bath facilities. ADUs are allowed up to two bathrooms.

Fire Requirements

ADUs must also comply with requirements set by the Bureau of Fire Prevention, in compliance with the California Fire Code. Fortunately, these requirements are often consistent across property and ADU types.

For example, if the primary residence is protected by fire sprinklers, the ADU must also be protected by sprinklers. As for attached ADUs greater than 500 square feet attached to a main unit with more than 3,600 square feet, both the ADU and main unit must have fire sprinklers.

You’ll also have to think about the ADU’s address (so that firemen can easily identify the unit when called). If your ADU’s address is not visible and legible from the street, your project may require a Fire Variance.

Also, if the distance from the curb to your proposed ADU is greater than 200 feet, as measured along a clear three-foot path to all sides of the ADU, you will need a separate Fire Variance.

Then, there’s the fire hydrant.

The closest available fire hydrant must have a minimum flow of 1,000 gpm at 20 psi. You will need to contact your water company for this information and must supply a letter from your water company verifying this information with your application materials. And if any of your exterior walls are more than 600 feet from the nearest fire hydrant, you’ll need a Fire Variance.

Parking Requirements and Exemptions

Last but not least are parking requirements. Unless you qualify for exemptions (many ADUs do) you are required to provide a parking space as part of your ADU.

You are exempt if:

  • Your ADU is within half a mile of a public bus or rail station
  • Your ADU is part of the primary residence or pre-existing accessory building
  • The ADU is built on a street with on-street parking permit requirements, where a permit has not been offered to the ADU occupant
  • The ADU is located within one block of hourly and daily motor vehicle services
  • Your ADU is part of a historic district

If you create an ADU by converting your garage, you are not required to replace the parking spaces.

Navigating San Jose ADU Requirements

When the going gets rough, you want to be there for your family. That’s why we’re here–to help you understand San Jose requirements for ADUs in 2020 and create a residence that is truly a home for the whole family.

We’re ADU builders specializing in designing, building, and permitting ADUs for families just like you. We serve over 20 cities and jurisdictions across the Silicon Valley area, bringing more than 30 years of experience as builders and housing advocates.

Ready to talk about your project? Get in touch today to let us know how we can help.

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