adu san jose

Filling the Gap: A Complete Adu San Jose Guide

So far in 2021, San Jose has issued 364 permits for ADUs. This is already more than the total for 2020.

San Jose is focusing on backyard homes as a way to fill its chronic housing shortage. The city has made the permitting process easier over the last few years. 

Are you looking to add independent living space to your property? Or would you like to invest in your property value or passive income from a rental?

An ADU could be the solution. Learn more about building an ADU in San Jose so you can decide if it’s the right choice for you.

Types of ADUs in San Jose

San Jose allows several types of accessory dwelling units (ADUs). The city has followed changes in state law and relaxed some of the restrictions on ADUs. You have more flexibility when deciding how an ADU will best fit with your existing home.

All types of ADUs need to have a permanent kitchen, bath, and sleeping space.

Detached, Attached, or Junior ADU

San Jose now lets you build a detached, attached, or junior ADU (JADU). A detached ADU is a permanent structure that is separate from the main residence. You can convert a detached garage or accessory building like a shop into an ADU.

An attached ADU shares a wall or roof structure with the main house. An attached ADU is a good option if your property isn’t big enough for a detached one.

A JADU is a separate housing unit in your home. JADUs are often a conversion of your attic, basement, or garage. These are the most uncommon ADUs.

Number of Bedrooms and Bathrooms

You now have more options when deciding how many bedrooms and bathrooms you want your ADU to have. An ADU in San Jose can be a studio, with a combined sleeping and living area.

A one bedroom or two bedroom floor plans are also allowed. The maximum bedroom size is 400 sq ft.

The ADU can have up to two bathrooms. A JADU can share the bathroom with the main residence or have a half or full bath.

Zoning Rules for an ADU

The regulations for ADU zoning have loosened in San Jose, but you still need to be sure your property is eligible. San Jose allows ADUs in four residential zones:

  • R-1 (single-family residential)
  • R-2 (two-unit residential, like duplexes)
  • RM (multi-family residential, like an apartment complex)
  • PD (planned development), if it allows single-family use

You can also build an ADU in a low-density cluster development if:

  • The development meets R-1 standards, or
  • The ADU meets the standards of the low-density cluster

Finally, you can put an ADU on a lot with an existing single-family home with one of the following designations:

  • Residential neighborhood
  • Urban village
  • Transit residential
  • Urban residential
  • Downtown
  • Mixed-use neighborhood
  • Mixed-use commercial
  • Rural residential

This range of options makes it more likely that your property will be eligible for an ADU. For single-family zoning, you may be able to add one ADU and one JADU. For a duplex, two detached ADUs and one attached ADU may be allowed.

For multi-family properties, you may be able to add a number of attached ADUs equivalent to no more than 25% of existing units.

Zoning regulations can be complicated. A reputable ADU builder will help you be sure your property meets the requirements.

Lot Size for an ADU in San Jose

The city of San Jose removed the minimum lot size requirement for an ADU. However, the maximum square footage of the ADU depends on the size of the lot.

A lot with an area of up to 9,000 sq ft can have an ADU with a floor area up to 1,000 sq ft. The floor area of an attached ADU can’t be more than 800 sq ft or 50% of the size of the existing primary dwelling.

A lot with an area greater than 9,000 sq ft can have an ADU with a floor area up to 1,200 sq ft. An attached ADU can’t be more than 1,000 sq ft or 50% of the square footage of the primary dwelling.

In addition, the total coverage of the backyard by structures can’t be more than 40% of the total area or 800 sq ft.

Placement of an ADU

San Jose regulations specify where on your property you can put an ADU. The requirements depend on whether the primary residence is a single-family or multi-family dwelling.

Placement of an ADU on a Single-Family Property

If the main residence is a single-family home, a detached ADU must be in the backyard or at least 45 ft from the front property line. The ADU must be at least 6 ft from the primary residence.

An attached ADU must share a wall or roof structure with the main residence. It can’t have more than 10 ft of separation from the main home. An attached ADU in the front yard can’t have the front door on the same side as the main residence, with some exceptions.

A JADU must be entirely within the existing footprint of the primary dwelling.

Placement of an ADU on a Multi-Family Property

A detached ADU must meet the same criteria as for a single-family property. An attached ADU can only be a conversion of an existing non-living space, like an attic or basement. JADUs aren’t allowed.

Other Requirements for an ADU in San Jose

You have several other regulations to comply with when planning your ADU in San Jose. Complying with all the requirements will help you get an ADU permit in San Jose more easily. The city provides an ADU Universal Checklist with all the requirements.

Property Designations

If your property is in a flood zone or geohazard zone, you have additional standards to follow. A dedicated easement on the property or a location in a Historic District have specific regulations as well.


In addition to the other regulations for placing the ADU on your property, you need to comply with the setback requirements. The amount of setback depends on whether the main dwelling is a single-family or multi-family residence. Attached and detached ADUs have different requirements.


An ADU needs a designated parking space. However, many ADUs qualify for an exemption. If you convert a garage into an attached ADU, you don’t need to create a replacement parking space.

Fire Safety and Access

An ADU needs to comply with the California Fire Code. This includes proximity to a fire hydrant that has enough water flow. Requirements for fire sprinklers may apply.

The distance from the street curb to the ADU must be no more than 200 ft.

Building Your ADU in San Jose

Starting the process to build your ADU in San Jose is exciting, but it can also be complicated. You need to be sure your design meets all the city and state requirements. Then you can apply for your ADU permit in San Jose and start construction.

Acton ADU is ready to be your partner throughout the new home process. We start with transparent and quality design. We’ll guide you through the administrative hurdles and build an ADU that will stand the test of time.

Contact us today to take the first step with an ADU specialist.

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