Frequently Asked Questions

How many square feet can I build on my lot?
For a single-family (R1) property, the maximum amount of buildable square footage (floor area) is determined by the size of the lot:

  • For lots under 11,000 square feet, the maximum floor area is 35% of the net lot area.
  • For lots above 11,000 square feet, the maximum floor area is 3,850 square feet plus 10% of the remaining lot area.

Example: If a lot is 15,000 square feet in size, it would be allowed 3,850 square feet + 400 square feet for a maximum allowable floor area of 4,250 square feet. (15,000 – 11,000 = 4,000 x .10 = 400)

Note: Net lot area is the total square feet of the lot minus any public and private street right-of-ways. For properties in other zone districts, contact the Planning Division at (650) 947-2750 or at planning@losaltosca.gov.

What’s the difference between floor area and lot coverage?
Floor area is the space enclosed by four walls on each floor of a building. It is measured to the outside edge of the exterior walls and includes halls, stairways, service and mechanical equipment rooms, interior courts, garages, carports and enclosed accessory structures. It does not include basements.

Lot coverage is the area of a site that is covered by the footprint of all structures, both open and enclosed, that are over six feet in height. A building footprint is measured to the outside edge of exterior walls and/or supports and includes covered porches, gazebos and trellises.

When is a design review approval required and what is the process for a single-family residential (R1) property?
Design review is required for all new construction, additions and exterior modifications to existing structures. For single-family residential projects, one-story design review applications are reviewed and approved at the staff level, and two-story design review applications are reviewed and approved by the Design Review Commission at public meeting. Submittal requirements for a residential design review application are as follows:

For additional information about the design review process, contact the Planning Division at (650) 947-2750 or at planning@losaltosca.gov.

What is my property’s zoning designation?
If you know your property’s cross streets, you can locate the zoning designation on the City Zoning Map. If you are unable to find your property on the map, contact the Planning Division at (650) 947-2750 or at planning@losaltosca.gov.

What if I have a non-conforming business?

A nonconforming business use is a lawful use existing on the effective date of a new zoning restriction that has continued since that time.  In downtown Los Altos, for example, office and personal service businesses are no longer allowed on the ground floors on Main or State Streets, though many of these types of businesses still operate.  The underlying policy of the law is for the eventual elimination of nonconforming uses; however, a new zoning ordinance may not compel the immediate discontinuance of an otherwise lawfully established use or business.

Section 14.66.110 of the Los Altos Municipal Code governs nonconforming uses and the abandonment and discontinuance of them.  This section states:

“An abandoned or discontinued nonconforming use in any district may resume if occupancy reoccurs within one hundred and twenty (120) days of the date the use was originally abandoned or discontinued.  A nonconforming use which has been abandoned or discontinued for more than one hundred and twenty (120) days may resume upon the granting of a use permit in accordance with the provisions of Chapter 14.80 of this title.  Whenever a nonconforming use changes to a conforming use, the use of the structure and/or site thereafter shall be conforming.”

For the purposes of this section, occupancy is established either by physical occupancy or by the issuance of a valid building permit to modify the building space.

Do I need a permit to remove a tree?
In general, all trees with a circumference of 48-inches or greater measured at 48-inches above the ground are protected and require a Tree Removal Permit in order to remove. In addition, the following trees also require a Tree Removal Permit before removal:

  • Any tree located within the public right-of-way
  • Any tree designated as Heritage Tree by the Historical Commission
  • Any tree that has been required to be saved or planted as part of a development approval
  • Any tree on a property with a pending development review application

Note: For a residential property with a two-story house, check with the Planning Division before removing trees of any size as they may be providing privacy screening and protected.

For more information, view the City's Tree Removal Criteria and Process or contact the Planning Division at (650) 947-2750 or at planning@losaltosca.gov.

Where can I locate a new air conditioning unit on my property?
The sound rating of an air conditioning unit determines the minimum distance to the property line. For more information, view the air conditioning equipment setback requirements.

Do I need a permit to build or rebuild a fence?
A permit is not needed to build or rebuild a fence, but the fence must comply with the City's fence regulations.

What is a second living unit?
A second living unit is a second dwelling on a single-family (R1) property that is subordinate to the main dwelling. In general, it is the addition of a kitchen to an accessory building or the addition of a second kitchen within an existing dwelling. The maximum size of a second living unit is 800 square feet.

  • Lots that are a minimum of 13,000 square feet are allowed to have a second living unit converted from existing floor space inside a single-family house.
  • Lots that are a minimum of 15,000 square feet are allowed to have a detached second living unit.

For more information, view the City's second living unit requirements.

When does a project require review by the Historical Commission?
Any property that is listed on the City's Historic Resources Inventory as a Historic Landmark, Historic Resource, Heritage Tree or within a Historic District is subject to the City's Historic Preservation Ordinance and requires review by the Historical Commission for any new construction, additions or exterior alterations. For more information, view the City's Historic Preservation Regulations. To find out if your property is listed on the Historic Resources Inventory, contact the Planning Division at (650) 947-2750 or at planning@losaltosca.gov.