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Hillsborough ADUs

Everything about building Accessory Dwelling Units in Hillsborough, CA

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Hillsborough ADU Guidelines Last Updated 04/05/20

PLANNING OFFICE The city has closed all operations during the COVID-19 outbreak. More information will be posted here once it becomes available. In the meantime, we are providing services for Hillsborough properties based on recent projects and research.

The city government of Hillsborough will approve ADUs under California's statewide mandated regulations.
The California Building Code (CBC) 2019 is adopted.
Relevant state bill updates for SB13, AB68, AB881, AB670 are shown in green below.


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City Hint: The city has not yet responded to requests for ADU permit volumes for the past year, but they will be provided here once response has been received.


Number of ADUs allowed:

According to state law, all single-family homes are allowed at least one ADU. Additionally, single-family properties which are owner-occupied may create one ADU and one Junior Accessort Dwelling Unit (JADU). Also, multi-family properties may now add one ADU per every four existing residential units, so long as they were legally established.

As of January 1st, 2020

Types of ADUs allowed:

Detached ADU, Attached ADU, Junior ADU are approved. Accessory Dwelling Unit (ADU)s may be new construction or converted from existing space. Junior ADUs must be converted from existing space.

Lot size:

Accessory Dwelling Unit projects on single family or multi-family residential parcels will not be subject to the minimum lot size of the underlying local zoning code or by special ordinance. ~ AB-68

As of January 1st, 2020

ADU size:

Single-family and multi-family Properties will be permitted to construct up to 850 sq.ft. for a one bedroom ADU or up to 1,000 sq.ft. for a two bedroom ADU, regardless of the underlying zoning standards of the property. A Junior Accessory Dwelling Unit up to 500 sq.ft. is permitted. The minimum size of any living unit (including ADUs and Junior Accessory Dwelling Units) is 150 sq.ft. according to Califronia Residential Code. ~ AB68 & AB881 Update

As of January 1st, 2020

Setbacks:

The maximum required setback for a detached new construction Accessory Dwelling Unit (ADU) shall be no more than 4 ft. from the rear and side property lines. Setbacks will not be required for Accessory Dwelling Unit (ADU)s and Junior ADUs converted from existing space that was legally eastablished. Attached Accessory Dwelling Unit (ADU)s and conversions from existing space to be expanded will be required to comply with the setbacks of the underlying zone. ~ According To AB68

As of January 1st, 2020

Parking:

Lots which convert an existing garage to an ADU or Junior Accessory Dwelling Unit will not be subject to replacement parking requirements. ~ AB68 & AB881 Update

As of January 1st, 2020

Fire Safety:

Per state requirements.

Shape, materials and style:

New construction/exterior changes (if any) should be designed to be compatible with the architectural style and detailing of the primary unit.

Height:

Height of the ADU will be determined by the maximum height of the underlying zone.

Design review:

For the required approval by the Planning Division, the Planning staff can approve most new ADUs administratively. If staff approval is not possible, the application will require approval by the Town’s Architecture and design review Board.

After approval from the Planning Division is secured, construction drawings may be prepared and submitted for the Building Permit application.

Number of Bedrooms:

Not specified by State Standards.

Ownership:

Owner-occupancy will not be required for new ADUs (conversion and new construction) built between 2020 and 2025. ~ SB13 Update

As of January 1st, 2020

Utility connections:

Local health officer approval where a private sewage disposal system is being used, if required. (State requirements)

There are no fees for the Planning Division review and there are no Building Permit fees for second units; Building Division plan-checking and other related fees do apply.

SB13 Update: As of January 1st, 2020, local impact fees for ADUs will be reduced substantially statewide.

Definition:

The term “second unit” means a residential dwelling unit that provides complete independent living facilities for one or more persons and is located on the same lot as the main house (called the “primary dwelling”). The second unit includes permanent provisions for living, sleeping, eating, cooking, and sanitation.

Allowed Zones:

*** Beginning in 2020, according to state law, all residential zoning districts, including single-family and multi-family, are allowed to build Accessory Dwelling Units. ***

As of January 1st, 2020

Lot Coverage:

The second unit must be constructed within the allowable maximum permitted floor area (FAR) and lot coverage of the applicable zoning district.

Conversion of Existing Space

Conversion of existing residential space (where there is no new construction proposed):
To secure approval of the conversion of existing space, first secure Planning Office, then Building
Department approval:
1. To secure Planning approval of the second unit, submit a completed Second Unit application,
demonstrate (with photos, a site plan, etc.) there is sufficient parking on the property for both the
primary and the second unit, and complete the request for the preparation of the document (for which
there is a fee for the City Attorney’s Office) to be recorded to alert future owners of the regulations
regarding a second unit. Submit these items to the Planning Division for approval. Once evidence of
the recordation of the required document is received, Planning Division approval will be granted.
2. After securing Planning Division approval, the applicant shall obtain all necessary permits and
arrange an inspection by the Building Division. The Building Division will check for any significant
health or safety problems. If there are repairs required, the applicant will work with the Building
Division to correct them. If there are no safety or Code problems, the second unit will be approved.

SB13 Update: Amnesty program to permit unpermitted units will be administered statewide, allowing non-health and safety code violations to be deferred.

Residential Building Code:

The California Building Code (CBC) 2019 is adopted.

Hillsborough City Planning Offices
Permitting

Hillsborough Building Department

1600 Floribunda Ave. Hillsborough, CA 94010 Hillsborough, CA 94010

Read Hillsborough Housing Market Update

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ADU Example Designs

ADU Model 480 sqft

W 24 ft L 20 ft

ADU Model 450 sqft

W 30 ft L 15 ft

Hillsborough ADU Marketplace

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Featured Financing Program

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CA Statewide


Tailored to ADU construction.
Based on project size & appreciation.
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Karyn Jones

Program Representative

Call Now (760) 496-5959

Read Hillsborough Housing Market Update

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Costs / ROI

SELECT ADU SIZE & TYPE

APPRECIATION ESTIMATE

* upon completion of ADU

CONSTRUCTION COST ESTIMATE

* based on local average price per sqft

RENTAL ESTIMATE

* estimated by location

MORTGAGE ESTIMATE

* 30 years / 5% interest rate / 20% down payment

SELECT ADU SIZE & TYPE

Size: 500 sqft

BASED ON LOCAL AVERAGE PROPERTY DATA & VALUE

Appreciation Estimate = (Base Value: $) / (Home's Living Space: sqft) * (ADU's Living Space: sqft)

Rental Estimate = (Rent Per Sqft: $3.25) * (ADU's Living Space: sqft)




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