1. Detached, stand-alone ADU
2. Basement ADU
3. Garage conversion ADU
4. Above-garage ADU
5. Internal ADU
6. Bump-out ADU
ADUs are allowed in residential zones R-1, R-2, and now also in R-M, and in PD (planned development) zones, subject to approved development standards. Where ADUs are prohibited in a PD Zone, such prohibition continues. What this means: Where most single-family homes exist, one ADU may be allowed, subject to standards outlined in the Municipal Code and in planned development districts.
In San Jose to build a granny flat your lot must be a minimum of 3,000 square feet to build an ADU. The impact of this is largely in older neighborhoods that tend to have smaller lots. For reference, most standard size urban lots are at least 5,000 square feet. So this is a pretty lenient minimum lot size requirement.
Min/Max Building SizesSan Jose limits your ADU square footage based off your lot size.
3,000-5,444 = You can build a one bedroom ADU up to 600 square feet.
5,445-9,000 = You can build a one bedroom ADU up to 700 square feet.
9,0001-10,000 = You can build a two bedroom ADU up to 800 square feet.
10,001+ = You can build a two bedroom ADU up to 900 square feet.
Maximum height for 1-story ADU is 18 ft. An ADU over a detached structure or a 2-story ADU are now allowed, with a maximum height of 22 ft.
1 story conversions have a zero foot setback requirement. New construction or ADUs that are built above a garage must have a minimum setback of 5 feet.
Detached garages or accessory structures may be converted to an ADU. A converted garage that has zero rear and side setbacks may maintain those setbacks, but any 2nd-story detached ADU must have a minimum 5-foot setback from the rear and side property lines. Attached ADUs must follow the setback rules for the main dwelling unit.
In alignment with recently enacted State laws: An ADU requires 1 space unless the property qualifies for an exemption. If a garage has been converted, the main dwelling parking spaces must be replaced. They may be uncovered and located in front or side setback areas. The homeowner may eligible for a reduction of one space of required parking per Municipal Code Section 20.90.220.B.1.b. Parking spaces may be configured on-site per state law.
Parking not required if the ADU is:
- Located within ½ mile of public transit
- The ADU is part of or within the primary residence or existing accessory building.
- Located within an architecturally and historically significant historic district
- Part of an existing primary residence or an existing accessory structure
- In an area where on-street parking permits are required, but not offered to the occupant of the ADU
- Is located within one block of a car share area.
Owner occupancy is not required in San Jose.
You may rent the accessory dwelling unit long-term.
How to Evaluate ROI
People often underestimate the cost to build a small unit. There are a lot of fixed costs and the expensive square footage, like a kitchen and bathroom, are not offset by large cheaper square footage (for example, large living rooms, hallways, and multiple bedrooms).
With that being said, building an accessory dwelling unit, especially if you intend to keep the property for a few years, represents an enormously beneficial opportunity to maximize your property.
By constructing an accessory dwelling unit you are adding additional square footage to the property. So if you can build a unit for $500 a square foot, but the average value of homes in your neighborhood are worth $636 a square foot you are gaining instant equity through the project. Plus, you also now have the added benefit of a flexible space that can be rented or used for family.
Property Value (avg value per sq ft)
$636 (Figure provided by Zillow)
Construction Costs (avg cost per sq ft)
$500 (Cost will vary depending on the size of the structure. The smaller you build the higher your cost per square foot will be)
Equity Gained through project
$636-500=$136 (Meaning you are gaining $136 in property value for every square foot built)
Ready to dive in? Check out our website www.eanovation.com
Rear Yard Coverage: Not including pools, not more than 40% of the rear yard may be covered.
Front Yard Paving: No more than 50% of the front setback may be paved with an impervious or previous surface.
Detached units do not need to meet any specific design standards. Attached ADUs and detached ADUs on properties listed on the Historic Resources Inventory must incorporate architectural style and elements of the primary dwelling.
ADU Fees for San Jose:
To get an estimate of permit fees associated with an ADU fill out and submit this worksheet: http://www.sanjoseca.gov/DocumentCenter/View/1865
In addition to a building permit fee, applicants for an ADU will be required to pay: