Accessory Dwelling Units (ADUs) are small homes designed for independent living. They can be on the same property as a single-family home or a multifamily building. ADUs are also called in-law units or granny flats, etc. They may be attached or detached from the main building.

Types of ADUs

Generally ADUs fall into these categories:

Attached – Sharing a common wall with an existing or new main building on a single-family home property.

Detached – Freestanding ADUs that are not attached to a proposed or existing main building.

Conversion – Built by converting parts of an existing space

Junior ADUs (JADUs) are a type of ADU that can be up to 500 sq. ft., created by converting parts of area within an existing or proposed single family home.

How many ADUs are permitted on my property?

The number and type of ADUs permitted varies between single-family homes (SFH) and multifamily homes (MFH).

¹ JADU not permitted for lots with 2 or more detached single-units on the same lot.
² Of the 3 allowed ADU types, a SFH lot cannot have both a Conversion ADU within the main building and an Attached New Construction ADU.

Permit Review Requirements

Your permit requirements depend on whether the project qualifies for a streamlined or non-streamlined review process.

Streamlined ADU (Planning Permit Not Required)

ADUs that qualify for streamlined review only require a Building Permit. The following ADUs qualify for streamlined review:

• New Construction ADUs up to 800 square feet on SFH lots
• New Construction ADUs on MFH lots
• Conversion ADUs
• JADUs
• ADUs completely within a new basement

Non-Streamlined ADU (Planning Permit Required)

If you plan to build a new ADU larger than 800 square feet on a single-family lot, you must first apply for a Miscellaneous Plan Permit (MPP). The Planning Division reviews this application to confirm your project meets City standards. After the Planning Division approves your MPP, you can submit your Building Permit.

• Non-Streamlined ADUs submittal requirements

Pre-approved ADU

The Plans Gallery lets you browse pre-approved ADU plans and connect with designers to purchase their plans. This can save time and money and simplify the ADU development process.

• ADU Pre-approved Plans Gallery – View pre-approved ADU plans that have a streamlined permitting process.

Legalize an Unpermitted ADU

If you built an ADU or JADU inside a permitted structure before Jan. 1, 2020, you can apply to legalize it. We may use reduced development standards if we find the unit safe to live in. Read the qualifications for denial of permit.

If you built the ADU after Jan. 1, 2020, you must follow the same rules that apply to new ADUs.

Deferred Enforcement for an Unpermitted ADU

If you built an ADU without a permit before Jan. 1, 2020, you may request a five-year deferred enforcement. You must apply to the Community Development Department. The City will review your submitted plans to verify life and safety requirements are met. The City must approve applications to ensure deferred enforcement.

Resources

Sunnyvale ADU Brochure – A concise summary of Sunnyvale’s ADU requirements

Santa Clara County ADU – Wealth of resources from the Santa Clara County Planning Collaborative.

Santa Clara County ADU Guidebook – A free step-by-step guide to building an ADU, including getting started, designing, financing and building.

Sunnyvale ADU Calculator – Provides a rough estimate of costs, fees and rents to help you create a budget for your ADU project.

Sunnyvale ADU Toolkit – A comprehensive guide to build an ADU in Sunnyvale