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Los Altos ADU Zoning and Building Standards

The zoning and building standards in Los Altos are designed to ensure that ADUs are constructed safely and harmoniously within the community. These standards regulate aspects such as size, height, setbacks, and parking requirements. Understanding these regulations is essential for a smooth and compliant building process.

Navigating the complexities of ADU regulations can be daunting, but we are here to assist you every step of the way. DevArt8 Construction team will provide guidance on zoning laws, design considerations, and the permitting process, ensuring your ADU project meets all local requirements and is completed efficiently.

Los Altos ADU Zoning and Building Standards

Property Requirements

Before planning your ADU, it is important to ensure your property meets the basic requirements. These include lot size, zoning classification, and existing structures on the property. Verifying these requirements early can save time and prevent potential issues down the line.

Building Size

The size of your ADU is subject to specific regulations depending on the zoning of your property. Typically, ADUs must be a certain percentage of the main dwelling’s size or have a maximum square footage limit. Adhering to these size limitations is essential for compliance.

  • Single-Family Zoned Lots:

For single-family zoned lots, ADUs must comply with specific building standards that dictate size, height, and setback requirements. These standards ensure that the ADU complements the existing residential structure and the surrounding neighborhood.

  • Duplex Family Zoned Lots:

In duplex family zoned areas, ADUs are subject to similar regulations as single-family zones but may have additional requirements or allowances. It is important to check local ordinances to understand the specific standards for duplex zoned properties.

  • Multi-Family Zoned Lots :

Multi-family zoned lots offer more flexibility in ADU construction. Property owners can often build both attached and detached ADUs, providing more options for increasing living space and rental opportunities.

  • Attached ADUs:

Attached ADUs are integrated into the existing structure, sharing a wall with the main dwelling. These units must meet specific building codes and design standards to ensure safety and aesthetic coherence.

  • Detached ADUs:

Detached ADUs are standalone structures on the same property as the main dwelling. They offer more privacy and flexibility in design but must adhere to zoning regulations regarding size, height, and setbacks.


Owner-occupancy requirements ensure that either the main dwelling or the ADU is occupied by the property owner. This regulation helps maintain the residential character of neighborhoods and promotes responsible property management.

Number Of Units Allowed

The number of ADUs allowed on a property depends on the zoning classification and lot size. Understanding these limitations is crucial for planning and ensuring compliance with local regulations.

Los Altos Building Height

Building height restrictions vary depending on the zoning of your property. These restrictions are in place to preserve the character of the neighborhood and prevent overshadowing adjacent properties.

  • Single-family: In single-family zones, the maximum height for ADUs is typically limited to one or two stories, depending on local regulations. This helps maintain the residential scale of the area.
  • Duplex family: For duplex family zones, height restrictions may allow for slightly taller structures compared to single-family zones, offering more design flexibility.
  • Multi-family: In multi-family zones, ADUs can often be taller, allowing for greater design creativity and more living space while still adhering to safety and aesthetic standards.

Los Altos Building Size

The size of ADUs in Los Altos is regulated to ensure they are proportional to the main dwelling and fit within the character of the neighborhood. These regulations help maintain a balanced residential environment.

  • Single-Family Freedom: Single-family zoned lots typically have more stringent size limitations to ensure the ADU is secondary to the main dwelling and does not overwhelm the property.
  • Duplex house: For duplex properties, size limitations for ADUs may be more flexible, allowing for larger units that accommodate more residents or additional amenities.
  • Multi-Family Mix: Multi-family zoned lots often allow for larger ADUs, providing more living space and potentially multiple units within the same property, fostering diverse housing options.

Fire Safety Regulations

Fire safety is a critical consideration in ADU construction. ADUs must comply with local fire codes, which may include requirements for fire-resistant materials, sprinkler systems, and accessible fire exits.


Parking requirements for ADUs vary based on zoning and property size. Ensuring adequate parking is essential for compliance and convenience, preventing potential issues with neighbors and local authorities.

Utility Connections

ADUs must have proper utility connections, including water, sewer, electricity, and gas. These connections must be installed according to local codes and inspected to ensure safety and functionality.


Setback requirements dictate how far an ADU must be from property lines, streets, and other structures. These regulations are crucial for maintaining privacy, safety, and neighborhood aesthetics.

Zoning Regulations

Understanding the zoning regulations specific to your property type is essential for ADU planning. These regulations dictate allowable uses, building standards, and other critical factors.

Los Altos ADU Zoning Regulations

Single Family

Single-family zones have specific regulations that govern the placement, size, and design of ADUs to ensure they complement the existing residential environment.

Duplex Family

In duplex family zones, regulations may provide more flexibility in ADU design and placement, accommodating the needs of multi-residential properties.


Multi-family zones offer the most flexibility for ADU construction, allowing for larger and potentially multiple units while still adhering to local building standards.

RF Zone Minimum Lot Area in Los Altos

In Los Altos RF Zone, minimum lot sizes range from spacious single-family homes (RF-20) to sprawling estate properties (RF-40), ensuring ample space for your ADU and lifestyle.

  • RF-20: For RF-20 zones, the minimum lot size ensures enough space for both the primary residence and the ADU, maintaining a comfortable living environment.
  • RF-30: RF-30 zones offer larger lot sizes, providing more flexibility in ADU design and placement, making it easier to comply with setback and size requirements.
  • RF-40: In RF-40 zones, the minimum lot size is even larger, allowing for expansive ADUs that provide significant additional living space without compromising the overall property layout.

Room Specifications

When planning your ADU, it is important to consider the specifications of each room to ensure comfort, functionality, and compliance with local building codes.

Los Altos ADU Room Specifications

Room TypeSpecifications
Bathroom– Minimum 1 bathroom
– Ventilation required
– Must include sink
– Toilet mandatory
– Shower or bathtub
Kitchen– Minimum 1 sink
– Cooking stove
– Refrigerator space
– Counter space
– Storage cabinets
Sleeping Areas– Minimum 1 bedroom
– Adequate ventilation
– Egress window
– Closet space
– Space for bed
Storage– Minimum 1 storage area
– Shelving optional
– Easily accessible
– Lockable if needed
– Dry and clean

Los Altos Requirements

ADUs in Los Altos must meet specific requirements to ensure they are safe, functional, and compliant with local regulations. These requirements cover aspects such as construction standards, utilities, and occupancy.

Detached ADU Los Altos: Detached ADUs are standalone units that provide privacy and flexibility. They must comply with specific regulations regarding size, height, setbacks, and utility connections.

Attached ADU Los Altos: Attached ADUs are built as part of the main dwelling, sharing a wall with the existing structure. These units must adhere to building codes and design standards to ensure safety and consistency.

JADU Los Altos: Junior Accessory Dwelling Units (JADUs) are smaller units typically created by converting existing space within the main dwelling. JADUs must meet specific size and utility requirements but offer a cost-effective way to add living space.

Rental Requirements

Renting out an ADU in Los Altos involves meeting certain requirements to ensure tenant safety and satisfaction. These include verifying tenant qualifications and maintaining the property.

  • Proof of Income: Prospective tenants must provide proof of income to demonstrate their ability to pay rent consistently. This helps landlords ensure reliable tenants.
  • Credit Score: A good credit score is often required to rent an ADU, reflecting the tenant’s financial responsibility and reliability.
  • Rental History: A positive rental history can indicate a tenant’s reliability and ability to maintain the property in good condition.
  • Application Fee: Landlords may charge an application fee to cover the cost of background and credit checks for prospective tenants.
  • Security Deposit: A security deposit is typically required to cover potential damages and ensure the tenant’s commitment to the lease agreement.
  • Proof of Renter’s Insurance: Tenants may need to provide proof of renter’s insurance to protect their personal belongings and cover liability in case of accidents.
  • Pet Policy: Landlords may have specific policies regarding pets, including restrictions on the type or number of pets allowed in the ADU.
  • Smoking Policy: Non-smoking policies are common to ensure the ADU remains clean and free of smoke damage, promoting a healthier living environment.

Development Standards for Los Altos ADU

Understanding the development standards for different types of ADUs in Los Altos is essential for planning and compliance. These standards ensure that ADUs are safe, functional, and harmonious with the surrounding neighborhood.

ADU TypesDevelopment Standards Specifications
Single-family– Max height: 16 feet
– Max size: 800 sq. ft.
– Setbacks: 4 feet
– Parking: 1 space
– Owner occupancy required
Duplex– Max height: 18 feet
– Max size: 1,000 sq. ft.
– Setbacks: 4 feet
– Parking: 1 space per unit
– Owner occupancy required
Multi-family– Max height: 20 feet
– Max size: 1,200 sq. ft.
– Setbacks: 5 feet
– Parking: 0.5 space per unit
– No owner occupancy requirement
Junior ADUs (JADUs)– Max size: 500 sq. ft.
– Must be within existing structure
– Separate entrance
– Kitchenette required
– Owner occupancy required

Los Altos Property Designations for ADU

When planning an ADU, it is important to consider specific property designations that may affect the construction process, such as flood zones, geohazard zones, and easements.

  • Flood Zones: Properties in designated flood zones must adhere to additional regulations to ensure the safety and integrity of the ADU. These may include elevated construction or additional drainage requirements.
  • Geohazard Zones: Geohazard zones, such as areas prone to earthquakes or landslides, have specific building requirements to enhance the safety and stability of structures. ADUs in these areas must comply with these standards.
  • Easements: Easements, which are legal rights to use another person’s land for a specific purpose, can impact where and how an ADU can be constructed. It is essential to review any easements on your property before planning your ADU.

ADU Permit Requirements And Fees

Constructing an ADU in Los Altos requires obtaining several permits to ensure the project meets all safety and building standards. Understanding these requirements and associated fees is crucial for a smooth approval process.

Elegant ADU In Los Altos

  • Building Permit: A building permit is required for the construction of any ADU. This permit ensures that the project complies with local building codes and standards.
  • Electrical Permit: An electrical permit is necessary for any electrical work involved in the ADU construction. This ensures that all electrical systems are installed safely and meet code requirements.
  • Plumbing Permit: A plumbing permit is required for any plumbing work, including the installation of new pipes, fixtures, or systems. This ensures the ADU has safe and functional plumbing.
  • Other Permits: Depending on the scope of your project, additional permits may be required, such as permits for mechanical systems, fire safety installations, or structural modifications.

Design Your Dream ADU Today!

Designing your dream ADU in Los Altos is an exciting endeavor. By understanding the local regulations and requirements, you can create a functional, stylish, and compliant ADU that meets your needs. Whether you are looking to create additional living space for family members, generate rental income, or enhance your property value, our team of experts is here to guide you through every step of the process. Let us help you turn your vision into reality and enjoy the many benefits of an ADU in Los Altos.


Yes, but specific setbacks and design considerations apply. Contact the Los Altos Planning Department for detailed guidance on navigating unique lot shapes.

Some lenders offer ADU loans, but traditional home loans can also be used for ADU construction, especially if they add value to your property.

Yes! The State of California offers various ADU incentive programs, including grants for low-income homeowners and developers. Research state and local programs to see if you qualify for financial assistance.