STATEWIDE UPDATE: New California ADU Bills SB13, AB68, AB881, AB670 have passed. These laws will create more options for building an ADU in Los Altos Hills in 2020. To prepare for the upcoming changes use our ADU Services to learn how these laws will effect your property!
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Los Altos Hills ADUs

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Los Altos Hills ADU Guidelines Last Updated 08/11/19


The city government of Los Altos Hills will approve ADUs under California's statewide mandated regulations.
The California Building Code (CBC) 2016 without amendments is adopted.
Relevant state bill updates for SB13, AB68, AB881, AB670 are shown in green below.


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:

One ADU per one primary dwelling.

AB68 & AB881 Update: Properties which convert existing space to create ADUs may be eligible for one ADU -AND- one JADU.

Types of ADUs allowed:

Attached, Detached and junior ADUs.

Lot size:

One acre minimum. For the purpose of calculating the 1.0 acre minimum lot size to allow ADUs, property adjacent to the parcel which was dedicated to the Town for roadway right-of-way shall be included, if the dedication was made as a condition of a site development approval for that parcel. Right-of-way dedicated through the subdivision process or purchased by the Town shall be excluded from the lot area calculation. The policy also clarifies that land dedicated for street right-of-way during the site development process is not to be deducted from the lot acreage relative to the minimum 1.0 acre lot size required for a ADU.

AB68 & AB881 Update: Properties will not be subject to minimum lot standards by ordinance or of the applicable zoning district.

ADU size:

The ADU shall not exceed one thousand (1,000) square feet of floor area; that detached structures for habitation, which might be used as rental units, are limited in number (one) and size (1,000 square feet);

AB68 & AB881 Update: Properties will be allowed up to 850 square feet for a one bedroom or up to 1,000 square feet for a two bedroom ADU.


Setbacks are determined by the standards of the underlying zone.

AB68 & AB881 Update: The maximum required setback for a detached new construction ADU shall be no more than 4 feet from the rear or side property lines.


Per state minimum requirements.

AB68 & AB881 Update: Properties which convert an existing garage will not be subject to replacement parking requirements.

Fire Safety:

Per state minimum requirements.

Shape, materials and style:

A ADU shall be subordinate to and architecturally consistent with the
primary dwelling;

The purpose of Code provisions regarding accessory structures and ADUs is to assure that such structures are subordinate to and compatible with the main residence on a lot;

If the ADU is within or attached to the primary dwelling, it shall be
constructed so that the entire structure appears to be one (1) dwelling;If the ADU is separate from the primary dwelling, it shall not be sited in a
visually prominent location, and shall respect the visual and acoustic privacy of primary dwellings on contiguous lots;


Height will be restricted to the maximum height of the underlying zone.

Design review:

Ministerial review Process per state standards.

Number of Bedrooms:

Not specified by State Standards.


Unit is not intended for sale separate from the primary residence and may be rented. (State requirements)

SB13 Update: Owner-occupancy requirements for ADUs will be voided statewide for 5 years.

Utility connections:

The lot on which an ADU is located must be connected to the public sanitary sewer system or have a private sewage disposal system that is deemed to be adequate for the addition of the accessory dwelling by the Santa Clara County Division of Health Services; and must have an adequate water supply;

Permit Fees

SB13 Update: Local impact fees for ADUs will be reduced substantially statewide.


“Secondary dwelling” means an attached or detached residential dwelling unit which provides complete independent living facilities for one (1) or more persons. A secondary dwelling shall include facilities for living, sleeping, eating, cooking, and sanitation, and be located on the same parcel under the same ownership as a primary dwelling. (§ 1, Ord. 305, eff. October 3, 1986; § 1, Ord. 327, eff. December 10, 1989)


Any vehicular access to a secondary dwelling shall be by a common driveway with the
primary dwelling;

Open Space & Views

The views of prominent scenic features by primary dwellings on contiguous lots shall be

Street & Traffic

The secondary dwelling shall not have a significant adverse impact on traffic flow and

Existing Structures

The Site Development Authority may determine that an accessory structure which does
not contain all of the elements of a “secondary dwelling” per the Zoning Code definition,
could readily be modified or used for independent living purposes. In such a case, the
Site Development Authority may, at its discretion, require a property restriction to be
recorded against the property title, limiting the use of the structure so that is it not
modified to a "secondary dwelling". The language of the restriction shall include
provisions for Town inspection and enforcement of this provision.

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) 2016 without amendments is adopted.

Los Altos Hills City Planning Offices


26379 Fremont Road Los Altos Hills, CA 94022 Los Altos Hills, CA 94022

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Los Altos Hills ADU Marketplace

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Karyn Jones

Program Representative

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Read Los Altos Hills Housing Market Update

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Costs / ROI


* upon completion of ADU


* based on local average price per sqft


* estimated by location


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


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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