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All ADU Regulations

San Jose, California

San Jose has updated their ADU ordinance to comply with new state laws for 2020. Below are the up-to-date requirements to permit an ADU in San Jose.
Updated Sep 16, 2023

San Jose, CA

ADUs are popping up all over the City of San Jose, and they’re only gaining momentum. The city issued over 1,500 ADU permits in 2022, a 30% increase from the previous year. With ADUs becoming more and more popular amongst homeowners across San Jose, here’s a rundown of ADU requirements to know for your San Jose ADU project as of 2023.

General ADU Requirements

While single-story standard ADUs (detached, attached, conversion) and Junior ADUs (JADUs) are permitted, JADUs must be converted out of existing living space.
Standard ADUs must be equipped for independent living and have permanent facilities for:
  • Living
  • Eating
  • Sleeping
  • Sanitation
  • Cooking Exterior access that is separate from the primary dwelling
ADU kitchens must also have:
  • A sink with running water
  • Countertops and cabinetry of a reasonable size
  • A refrigerator
  • A permanent range/cooktop that doesn’t need more than 120V or natural/propane gas
JADUs may share bathroom/sanitation facilities with the primary dwelling, but they must have a separate entrance. Conversion ADUs must also have their own entrance.

Zoning

All properties zoned for single family or multi-family with the following zoning codes are eligible for ADUs. Check the zoning of your property here:
  • R-1 (most single family homes)
  • R-2, R-M (duplexes & multi-family)
  • PD (planned development)

Fees

During the course of permitting your ADU project, you can expect to pay the following fees:
  • Permit Issuance Fee: You’ll need to pay a fee to secure your building permit. This fee depends on the size of your ADU.
  • Plan Review Fees: The plan review fee is charged to review the plans for the ADU and ensure that they meet all applicable building and zoning codes. This fee depends on the size of your ADU.
  • Water and sewer connection fee: If the ADU requires a new water or sewer connection, the homeowner will be charged a connection fee. The fee is based on the size of the ADU and the location of the property.
  • School impact fee: For new detached units over 750 square feet, a school impact fee is charged during the building permit stage for all residential property. Fee information varies based on school district.
  • Parkland fee: For new detached units over 750 square feet, parkland fees ranging from $1,700 to $8,900 will apply depending on the location.
  • Fees for other processes may be needed including: Geological Hazard Review and Clearance, Tree Removal Permit, and Fire Variance.

Number of units

The number of ADUs you’re able to build depends on how your lot is zoned.
  • Lots zoned for single family use may add 1 ADU and 1 Jr. ADU (JADU).
  • Lots zoned for duplex may be allowed to add 2 detached ADUs.
  • For multifamily, a number of attached ADUs equivalent to up to 25% of existing units may also be allowed (e.g. a building with 12 units may qualify for 3 attached ADUs).

Building size

Maximum building size is determined by your lot size, zoning and ADU type:

Single family zoned lots:

Up to 9,000 sq. ft.:
  • Detached ADU: 1,000 sq. ft. maximum
  • Attached ADU: up to 800 sq. ft. or up to 50% of the primary residence without exceeding 1,000 sq. ft. (e.g. for a 1,800 sq. ft. home, a 900 sq. ft. attached ADU is allowed
9,000 sq. ft. and greater:
  • Detached: 1,200 sq. ft. maximum
  • Attached: up to 800 sq. ft. or up to 50% of the primary residence without exceeding 1,000 sq. ft. (e.g. for a 1,800 sq. ft. home, a 900 sq. ft. attached ADU is allowed
Any lot with an existing JADU:
  • JADU: 500 sq. ft. maximum
  • Detached: 800 sq. ft.
  • Attached: not allowed with a JADU

Duplex & multifamily zoned lots:

Any lot size:
  • Detached: 800 sq. ft.
  • Attached: 800 sq. ft.
  • JADU: not allowed

Building height

Maximum building height depends on the zoning and ADU type:

Single family zoned lots:

  • Attached ADU: same height limitations as apply to the main dwelling unit
  • Detached ADU: One story: 18 ft. maximum; two-story: 24 ft. maximum; if the property already includes a JADU, height of the detached ADU is 16 ft. maximum

Duplex or Multifamily zoned lots:

  • Attached ADU: limited to a conversion of existing non-livable space and must maintain existing height
  • Detached ADU: 16 ft. maximum

Basements

Conversion of existing unfinished basement space can be used for an attached ADU.

Setbacks

Minimum setbacks are determined by the zoning and ADU type. For all corner lots, regardless of zoning type, a 10 ft. setback is required on the street side.

Single family:

  • Attached: same setback requirements as apply to the main home
  • Detached: must be set back 45 minimum from front property line, rear / side setbacks less than 3 ft. may be subject to fire mitigation measures; a 2nd story or new ADU with greater than 40% rear yard coverage must be set 4 ft. back from rear / side property lines.

Duplex or multifamily:

  • Attached: limited to the conversion of existing non-livable space
  • Detached: must be in the rear yard or 45 ft. from the front property line; minimum 4 ft., allows for up to 1 ft. projection for eaves; 2nd story must be 4 ft. set back from rear / side property lines

Parking

San Jose follows CA state law, where no additional parking is needed for an ADU if any of the following are true:
  • The accessory dwelling unit is located within one-half mile walking distance of public transit.
  • The accessory dwelling unit is located within an architecturally and historically significant historic district.
  • The accessory dwelling unit is part of the proposed or existing primary residence or an accessory structure.
  • When on-street parking permits are required but not offered to the occupant of the accessory dwelling unit.
  • When there is a car share vehicle located within one block of the accessory dwelling unit.

Owner-occupancy

Owner occupancy is not a requirement for permitting an ADU from January 1, 2020 until January 1, 2025. This is a great opportunity for rental property owners to increase their yields in a cost-effective way.

Rental

While long-term rentals are permitted for ADUs, short-term rentals (e.g. Airbnb for less than 30 days) are not permitted in San Jose.

Watch-outs

Do you have a utility easement over your property? Are you on a lot with special setbacks? A custom ADU might be right for you. Reach out to us and we’ll help you build a custom ADU to fit your unique property characteristics and local regulations!

FAQs

How close to my house can I build an ADU in San Jose?

When building a detached ADU, it should be at least 10 ft away from your primary residence. You cannot build a detached ADU in front of a single-family primary residence or within the front setback area of a multi-family home. It is a good idea to check such requirements with local authorities before starting your project.

Can I convert my garage into an ADU?

Yes, if you own a single-family or multifamily home in a residential-zoned area, you may convert your garage into an ADU in San Jose. Depending on the condition that your garage is in, the project may take under 9 months to complete and cost less than building a detached ADU. Reach out to our team to get an assessment on the condition of your garage and whether it can be converted affordably.

What is the smallest ADU I can build in San Jose?

Across California, the smallest ADU you may build is 150 sq. ft., regardless of type.

Does an ADU need a kitchen in San Jose?

Yes, ADUs must accommodate permanent and independent living, and be equipped with a fully functional kitchen.

Can I build 2 ADUs on my property in San Jose?

If your property is zoned for single-family living, then you may be eligible to build one Standard ADU (SADU) and one JADU. Multi-family properties may house up to two SADUs or conversion ADUs, but this may vary based on the number of dwelling units already on the property.

What is the difference between an ADU and a JADU?

ADUs may either be attached to or detached from the primary dwelling, while JADUs are contained entirely within the primary dwelling. ADUs must be equipped with permanent facilities for independent living, but JADUs need only have an “efficiency” kitchen and may share some facilities with the primary dwelling. The maximum size allowed for a JADU is 500 sq. ft., while two-bedroom ADUs in San Jose may be up to 1,000 sq. ft.

How much does an ADU increase property taxes in San Jose?

Thankfully, your existing property will not be reassessed if you build an ADU in San Jose! You can expect the value of your property to increase after you build your ADU. Since property taxes are often based on property values, this can increase your property taxes. However, any increases will only be based on the value of the ADU itself. Building an ADU will not trigger a reassessment of the value of your main home.

How many bedrooms can an ADU have in San Jose?

If your ADU is under 850 sq. ft., it can have up to one bedroom. If your ADU is larger than 850 sq. ft., it can have up to two bedrooms.

How long does it take to build an ADU in San Jose?

The entire process, from start to finish, would depend on the type of ADU you’re building, the scope of your project, and the area you’re building in. New ADU projects may take 4-6 months to design and permit, and an additional 4-6 months to build.

Can I rent my ADU in San Jose?

Yes, many homeowners we’ve worked with in San Jose rent out their ADUs, given the high demand for housing and high rents. Short-term rentals of less than 30 days are not allowed in San Jose, but you can rent out your ADU on platforms like Airbnb for 30+ days.

How many square feet can an ADU be in San Jose?

Depending on zoning conditions, setbacks and the number of bedrooms you are hoping to include, you may be allowed to build an ADU that has a maximum area of 1,200 sq. ft.

Can you build a 2-story ADU in San Jose?

As the height limit for an ADU is 16 ft, it is unlikely that you will be able to accommodate 2 stories.

Want to learn more about ADU regulations in your area?

Book a free consultation and estimate with a Cottage ADU Expert to find out what’s possible on your property!