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Santa Clara County, California: ADU Regulations

City or County:

Santa Clara County, California

Date Updated:



Allowable Urban Districts: R1/R1E/RHS/R1S/R3S/R2/R3

Allowable Rural Zones: A/AR/HS/RR

Allowable Commercial and Industrial: CN, CG, OA

Special Purpose: A1, RS

Number of ADUs:

One ADU and One JADU allowed in single-family. For multi-family lots, 25% of multifamily units are allowed for units converted from existing structure, plus two Detached ADUs per lot.

Types of ADUs:

Attached, Detached and Junior ADU



Maximum ADU Floor Area:


Primary Residences [< 1,600 sq.ft.] - 800 sq.ft. max;
Primary Residences [1,600 - 2,400 sq.ft.] - 800 sq.ft. min, ADU no more than 50% of primary residence
Primary Residences [>2,400 sq.ft.] - 1,200 sq.ft. max

Detached: 1,200 sq.ft. max. However, the law permits additional square footage:
- Decks and porches are limited to a cumulative 400 sq.ft. beyond the applicable dwelling sizes.
- Also, an attached garage or carport of up to 400 sq.ft. may be incorporated in the design of a Detached ADU, provided the dwelling portion does not exceed the applicable maximum floor area of 1,200 sq.ft.
- An Attached Junior ADU may be incorporated into the Detached ADU, and the cumulative square footage shall not exceed 1,700 sq.ft.

Lot Coverage:

Must adhere to coverage limits of underlying zoning district. A cumulative total of 800 sq.ft. for all ADUs on a lot in the n1 or n2 combining district shall not be included in floor area calculations




No min/max


Require separate kitchen facilities.


ADUs require separate bathroom facilities.

Junior ADUs may include separate bathroom or may share bathroom with existing structure.

Note: Drainage and sewer connections should be assessed on a project by project basis.


One off-street parking space per unit required for standard ADUs. None are required for Junior ADUs.

Exemptions to providing additional parking space:
• ADU is within one-half mile of a public transit stop
• ADU is within an historic district
• When existing square footage is converted to an ADU
• When on-street parking permits are required but not offered to the ADU occupant
• When a car share vehicle is located within one block of the ADU


Front - follow guidelines of underlying zoning district.

4’ Rear and 4’ Side

Note: Fire Department regulations should be assessed on a project by project basis.


Same as primary dwelling if ADU complies with residential setbacks, otherwise 16’. Detached ADUs over 16’ must incorporate a hip, gable, or other similar styled roof design


Urban ADUs may be no nearer than 6' to primary dwelling.

Rear Yard Coverage:

Must follow requirements established by zoning district in which lot is located.


Unless noted on Priority Lists No. 1 and 2, design standards are advisory. Certain features, materials or forms may be required by means of design review or ASA approval. New ADUs in D, D1, D2, or SR are subject to a light reflectivity value (LRV) requirement of 45 or less for façade and roof.

Note: Historic Neighborhoods or Districts should be assessed on a project by project basis.



Source Code:

Important Note: Rules and regulations are updated and changed frequently. It’s one of our jobs to be up to speed and navigate those regulations. Let us know if our website isn’t up to date or if you have any information that could help. Cheers!