san jose adu requirements

What Are San Jose ADU Requirements?

Recent events have shown us the importance of keeping families together. Today one in four Americans live in multigenerational households. This is an increase of 15% in the last ten years!

If you live in the San Jose area, adding an ADU to your property could be a great solution. San Jose’s mayor is committed to expanding the local housing supply by building backyard homes.

ADUs allow you the very best of multigenerational living. Family members are close by while still maintaining independence.

Let’s explore the San Jose ADU requirements to find out what you need to know about adding an ADU to your home.

San Jose ADU Requirements: An Overview

ADU stands for Accessory Dwelling Unit – a separate dwelling within the boundary of an existing family home. You may be more familiar with the term granny flat or secondary unit.  Everyone in the family gets their own private space while still being in close proximity to one another.

An ADU can be fully detached from the existing property. It can also be attached, joined either by a wall or by sharing a roof structure.

It’s important to note that JADU requirements are not discussed in this article. A JADU is created within the walls of an existing family residence. 

In order to build an ADU in San Jose, you must first obtain a permit from the City of San Jose. The City of San Jose requires that all ADUs meet the California Building Code and the San Jose Municipal Code.

In addition, the City of San Jose has specific requirements for ADUs, which include but are not limited to:

  • Maximum size
  • Placement on the property
  • Setback from the property line

Let’s dig into the requirements in more detail.

San Jose’s Accessory Dwelling Unit Regulations

The City of San Jose has created an ADU Universal Checklist. This combines state laws for adding an ADU in California with San Jose Municipal Code.

This should be the starting point for any homeowner or developer considering adding an ADU to an existing or new-build property. It includes the following areas:

  • Properties that qualify
  • Property designations
  • Development Standards
  • Fire safety & emergency access
  • Miscellaneous

Before creating building plans, it’s important to complete the checklist. This will help you to determine whether your ADU project is likely to be green-lighted. 

Properties That Qualify

Your property must be in the correct area and zone to be suitable for ADU development. Contact the San Jose Permits Office to determine whether:

  • Your property is within the jurisdiction of the City of San Jose
  • Your property is within a residential zone starting with R-1, R-2, R-M, or PD

Other General Plan designations also permit the construction of ADUs, including:

  • Residential Neighborhoods
  • Mixed-Use or Mixed-Use Commercial Neighborhoods
  • Urban Residential / Transit Residential / Rural Residential neighborhoods
  • Downtown or Urban Village

If your home does not fall into one of these zones, you cannot build an ADU on your property. If you are still unsure about the designation of your home, speak to a San Jose City Planner. 

In a single-family home, you can construct one ADU. In duplex or multifamily homes, two detached ADUs may be permitted. 

On a multifamily lot, it may be possible to build multiple ADS. For example, a building with 8 units may receive permission to build 2 ADUs, as the current rate is set at 25% of the existing units).

Property Designations

In addition to zoning requirements, you need to check additional property designations. This doesn’t mean that you can’t build an ADU, but you will need to meet extra requirements. These designations include:

  • Flood zones
  • Geohazard zones
  • Historic designation
  • Easements

There are four affected flood zones – A, AE, AH, and AO. Zones D and X are not affected by these requirements.

Bulletin #211 – ADU Building Plan Requirements sets standards for these homes. Your architect will need to set out:

  • Height of the floodplain
  • Lowest floor elevations
  • Flood vent calculations
  • Location and height of all machinery and equipment

If your home is in a geohazard or landslide zone, you will need to obtain a Geologic Hazard Clearance. You can obtain this from the Department of Public Works. Homes in Historic Districts have to comply with simplified design standards. 

Check the copy of your title to see whether there are any dedicated easements on your property. An easement gives rights to a third party to use or access land on your property. This could allow a utility company access to sewers, power lines, or gas mains on your property.

The easement may dictate that there can be no construction over the easement. It’s important to check these first before creating building plans.

Development Standards

As well as complying with the ADU zoning guide, all San Jose ADUs must meet development standards. These vary depending on the style of your home.

Single-family properties:

  • An attached ADU must share a wall or roof structure with the main residence
    • An attached ADU cannot have its front door on the same street-facing facade as the primary residence
  • A detached ADU must be either in the rear yard or 45 feet from the front property line
    • Must have 6 feet separation from the main home
    • Can be converted from an existing detached garage or accessory building, or be built to attach to a detached garage

Duplex and multifamily properties:

  • Attached ADUs must be converted from an existing office, basement, garage, or attic
  • Detached ADUs must be 45 feet from the front property line or in the rear yard
    • Must have a 6-foot separation from the main home

Size and Height Restrictions

The permitted size of an ADU depends on the size of the lot and the rear yard coverage limitation.

The rear yard (the area from the rear of the property to the rear boundary) must not exceed 40% coverage with structures or 800 sq. ft. 

The permitted sizes of ADUs on single-family lots are:

  • Lots of up to 9,000 sq. ft.:
    • Detached ADU – 1,000 sq. ft. maximum
    • Attached ADU – up to 800 sq. ft. or 50% of primary residence area, but not greater than 1,000 sq. ft
  • Lots of 9,000 sq. ft. or greater:
    • Detached ADU – 1,200 sq. ft. maximum
    • Attached ADU – up to 800 sq. ft. or 50% of primary residence area, but not greater than 1,200 sq. ft

If a lot already has an existing JADU, a detached ADU of up to 800 sq. ft. is permitted. If the home already has a JADU, you cannot add an attached ADU.

For duplex and multi-family lots, attached and detached ADUs of a maximum of 800 sq. ft. are permitted.

Setback Requirement

Setback requirements are simple for attached ADUs for single-family homes. They are the same as the main dwelling unit. Attached ADUs cannot be built on to existing duplex and multi-family homes, so there are no setback requirements.

For a single-family home, a detached ADU must be:

  • Set back at least 45 feet from the front property line
  • Have rear and side setbacks of 3 feet minimum, or else comply with fire mitigation measures
  • Two-story or new ADU with more than 40% yard coverage must be 4 feet from rear and side property lines

For a duplex or multifamily property, a detached ADU must be:

  • Situated in the rear yard or 45 feet from the front property line
  • Rear and side setbacks of a minimum of 4 feet
  • No second story allowed

There are additional requirements if:

  • The lot is greater than 1/2 acre and runs along a riparian (watercourse) corridor:
    • Minimum 100-foot setback
  • ADU has a deck, unenclosed entry landing, or second story balcony:
    • Minimum 15-foot rear/side setback needed
    • Not along building walls nearest rear and side property lines
  • Corner lots
    • 10-foot setback required on the street side

Height Limitations

In a single-family home, an attached ADU must comply with the same height limitations as the main dwelling.

Single-story detached ADUs have a maximum height of 18 feet. Two-story ADUs can reach a maximum height of 24 feet. If the property already has a JADU, the maximum height is 16 feet by state law.

Duplex or multifamily homes may build detached ADUs to a maximum height of 16 feet.

Sleeping Areas, Kitchen, Bathroom, and Storage

Your ADU may have a maximum of 2 bedrooms. Bedrooms must not exceed 400 sq. ft. in size. 

Kitchens must include permanent cooking facilities, such as:

  • A cooktop and oven or range
  • Counter space for food preparation
  • Sink
  • Cabinets for food storage

An ADU may have up to two bathrooms, including a sink, toilet, and bathing/showering facilities.

Any storage areas provided may not exceed 60 sq. ft.

Additional Requirements

Additional requirements apply to preserve the peace and privacy of the neighborhood. These include:

  • Second Story Window Sill – must be a minimum of 5 feet from the floor for walls nearest to rear and side property lines
  • Parking – check state law to find out whether you can receive an exemption.
    • If you must provide parking, it must have a minimum driveway length of 18 feet and be on a surface free of mud and dust
    • If you convert a garage into an attached ADU, you do not have to provide replacement parking

Fire Safety

Your ADU design must comply with the California Fire Code (CFC). It’s important to check the following before starting on building plans:

  • Hydrant water flow – a minimum flow of 1,00 gpm at 20 psi is required from the nearest hydrant
    • Write to the water company for this information. Include their response with your building permit application
  • Hydrant proximity – all exterior walls must be within 600 feet of a hydrant
  • Fire sprinklers – if the main property has sprinklers, the ADU must have them as well
  • Attached ADU sprinkler regulations
    • If ADU is greater than 500 sq. ft. and the overall area with the main unit exceeds 3,600 sq. ft. then the whole property needs a fire sprinkler system
  • ADUs must have their own address that is visible and legible from the street
  • ADUs with the following must apply for a Fire Variance:
    • Exterior walls greater than 600ft from a fire hydrant
    • Distance from the street curb to the ADU greater than 200ft


The final consideration is tree removal. You will need a permit to remove a heritage tree or an ordinance-size tree. In San Jose, an ordinance-size tree measures:

  • Single trunk – 38 inches or more in circumference at 4.5 feet above the ground
  • Multi-trunk – 38 inches combined circumference for all trunks at 4.5 feet above the ground

Your application will need to demonstrate that the tree restricts the economic development or improvement of the lot. 

Pre-Approved San Jose ADUs

Pre-approved ADUs have already been reviewed by the City of San Jose and are ready to build. You already know they have met the standards for code compliance and engineering, meaning that you save time and money.

The floorplan and design cannot be altered. However, there is a lot of scope to personalize these homes through bespoke interior design packages.

To qualify for this program, you must:

  • Be planning a detached ADU project
  • Be in a residential zone and have a single-family home or duplex on the plot
  • Not be in a geohazard, landslide, or flood zone
  • Not located in a WUI (Wildland-Urban Interface) area

Simply talk to an approved vendor to discuss pre-approved designs and how to obtain the right ADU permits. The city advises that contractors pull the permits for the projects on your behalf.

Meeting the San Jose ADU Requirements

The City of San Jose makes it as easy as possible for homeowners to determine whether ADU permits will be issued. Complete the Universal Checklist before making building plans. Once this is done, you can arrange a free consultation with a city planner to discuss the viability of your proposed design.

Creating Your San Jose ADU

There are many San Jose ADU requirements that homeowners must meet. But rest assured that the city is supportive of people’s efforts to add to the current housing stock in this way.

If all of this seems overwhelming, the simplest choice is to work with a trusted ADU contractor. One that has experience in meeting and exceeding the San Jose Municipal Code.

At Acton ADU, we keep up to speed with San Jose and California state regulations so you don’t have to. You can choose from one of our pre-approved designs or work with us to create your own bespoke ADU. 

The first step is a consultation with one of our ADU specialists. Call us today at (408) 819-2844 or contact us online to get started.

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