Mountain View ADU Zoning and Building Standards

California’s ADU legislation now allows property owners in Mountain View to build accessory dwelling units, presenting a potentially lucrative opportunity. To make the most of this, familiarize yourself with Mountain View’s use regulations for ADUs, which cover unit size and parking requirements. This ensures your project aligns with local policies and adds maximum value to your property.

Mountain View ADU Zoning and Building Standards

Property Requirements

Building Size

  • Single Family Zoned Lots:

Homeowners can build ADUs up to 1,200 square feet without a minimum size requirement. Detached ADUs are limited to 50% of the primary residence’s footage, while attached ones can reach up to 70%. Junior ADUs of up to 500 square feet inside the main home, including an efficient kitchen, are also permitted in the region.

  • Duplex Family Zoned Lots:

Detached ADUs are allowed up to 800 square feet each, aligning with the local guideline that limits them to 50% of the primary dwelling’s size. There is no specified minimum size for these units, providing flexibility for property owners. Unlike for single-family lots, attached ADUs are typically not permitted on duplex property lots in the Mountain View region.

  • Multi-Family Zoned Lots:

There’s no minimum size stated for constructing accessory dwelling units, while the maximum size allowed is 500 square feet per unit. It’s worth noting that detached ADUs are generally not permitted on properties with multi-family zoning. However, attached Accessory Dwelling Units, also known as Junior ADUs, are permissible within the confines of existing multi-family structures.


Mountain View currently doesn’t require owner-occupancy for ADUs. This means you can build and rent your ADU without residing in the main dwelling. This flexibility offers attractive investment opportunities for homeowners.

However, some exceptions exist:

  • State Density Bonus Law: If you utilize the State Density Bonus Law to increase allowable building density on your property, owner-occupancy might be required for a specific period.
  • Duplex Lots: For ADUs exceeding 500 square feet on duplex lots, the City encourages, but doesn’t mandate, owner-occupancy in either the main dwelling or the ADU.

Number of Units Allowed

Each single-family lot can support one ADU, with a potential Junior ADU within the main residence under certain conditions. Duplex lots typically accommodate one detached ADU per unit, while attached ones are not usually permitted. For multi-family lots, detached ADUs are prohibited, but each existing unit can integrate a Junior ADU into it.

Mountain View Building Height

  • Single-Family: The roof extends from the finished floor to its highest point, measuring 15 feet from the eave or ridge.
  • Duplex Family: The distance from the floor to the roof’s highest point, whether the eave or ridge, is about 15 feet.
  • Multi-Family: Generally, the same as the existing multi-family structure’s permitted height. JADUs within multi-family units must adhere to the interior height limitations of the main dwelling.

Mountain View Building Size

  • Single-Family: Create spacious ADUs up to 1,200 square feet, perfect for 2-bedroom living spaces. Enjoy flexible design options with no minimum size, allowing for cozy studios or inviting guest suites.
  • Duplex Family: Each ADU can have a maximum area of 800 square feet, making it a great option for cozy one-bedroom homes. Owners can explore different possibilities, including compact studio designs, without any minimum size requirement.
  • Multi-Family: Each unit is 500 sq ft, making them cozy studio apartments. You can even go smaller with no minimum size, which is perfect for creative unit plans.

Fire Safety Regulations

Sprinkler systems are usually required for units larger than 500 square feet or attached to the main home. Sleeping areas and adjoining hallways need interconnected smoke detectors. ADUs must have defined emergency exits, and secure egress pathways, and may require specific fire-resistant materials and construction methods.


ADUs may require extra parking spaces based on zoning and unit size. If you’re converting a garage or renting out the ADU, explore alternative parking options like on-street permits or a carport, and consider adding guest parking.

Utility Connections

Setting up individual meters for water, electricity, and gas is advisable for easier management. Evaluate the adequacy of your utility services to support the additional load, and secure the required permits and inspections for these installations.


Setback regulations require maintaining clearances from property boundaries and nearby structures to comply with local zoning rules, which may differ by area. Placement of ADUs should be strategized to minimize effects on sunlight exposure and shadows for your property and neighboring lands.

Zoning Regulations

Mountain View ADU Zoning Regulations

Single Family

Regulations allow a detached ADU up to 1,200 square feet or an attached ADU up to 70% of the primary residence’s footage. This flexibility enhances property value and utility for homeowners.

Duplex Family

Owners face more limitations with fewer configuration choices than single-family lots. Detached ADUs are permitted up to a maximum of 800 square feet, while construction of attached ADUs is generally not approved.


Restricted to a maximum size of 500 square feet for a compact living arrangement, preserving the neighborhood’s present density and character. While no detached ADUs are allowed, residents can still optimize their property’s value and functionality within these parameters.

RF Zone Minimum Lot Area in Mountain View

  • R-1: 5,000 sq. ft. – Typically allowing for comfortable single-family homes with some outdoor space.
  • R-2: 7,500 sq. ft. – Providing ample space for larger homes with yards and potential for pools or additional outbuildings.
  • R-3: 10,000 sq. ft. – Catering to even larger and more luxurious properties, such as sprawling estates and executive homes with grand landscaping and a focus on privacy.
  • R-4: 15,000 sq. ft. – The RF Zone is exclusively for remarkable properties, featuring exquisite mansions with expansive grounds, guest houses, and unmatched privacy.
  • R-5: 3,500 sq. ft. – Designated for denser development, featuring smaller single-family homes or townhouses.

Room Specifications

Mountain View ADU Room Specifications

Room Type Specifications
Bathroom –     Minimum floor area: 35 sq ft (including fixtures)

–     Must include toilet, sink, and shower/bathtub

–     Grab bars in shower/bathtub recommended

–     Ventilation required

Kitchen –     Minimum floor area: 40 sq ft

–     Must include a sink with hot and cold running water

–     Countertop space for food preparation


Appliance requirements vary based on ADU type:

– Junior ADU (JADU): Efficiency kitchen with microwave and mini-fridge only allowed

– Standard ADU: Stovetop or cooktop and oven or range required

Sleeping Areas –     Minimum number of bedrooms: 1 (studio layout allowed for JADUs)

–     Minimum floor area per bedroom: 70 sq ft

–     Closet with minimum hanging space required for each bedroom

–     Natural light and ventilation recommended

Storage –     Minimum total storage area: 5% of ADU gross floor area

–     Can be distributed throughout the unit (e.g., closets, cabinets)

Mountain View Requirements

  • Detached ADU Mountain View

Provide unique independent living quarters that can be leased independently from the main residence, offering both homeowners and renters increased flexibility. They necessitate individual utility metering and may not need separate parking, though they must adhere to specific setback requirements that provide a buffer from neighboring properties.

  • Attached ADU Mountain View

Blend with existing structures, sharing entries, and utility connections for a more integrated living experience. They offer a versatile housing solution with potentially shared parking and reduced setback requirements, maximizing the use of driveways and minimizing space between buildings.

  • JADU Mountain View

Offers a compact and efficient living space of up to 500 square feet, complete with a modest kitchen setup, seamlessly integrated into an existing single-family home. These units cleverly utilize the main home’s entrance and eliminate the need for dedicated parking, promoting a shared use of existing spaces.

Rental Requirements

  • Permits & Inspections:

Rental Permit: Required to ensure adherence to local codes before leasing.

Building Inspection: Verifies ADU conforms with all safety and habitability guidelines.

  • Lease Agreements:

Written Lease: Specifies conditions, including rent and maintenance duties.

Lease Duration: Not strictly regulated, yet one-year terms are typical.

  • Tenant Rights & Obligations:

Fair Housing: Discrimination against protected groups is prohibited.

Living Standards: Units must be sanitary with functional utilities and climate control.

Minor Maintenance: Tenants handle routine upkeep as agreed in the lease.

  • Additional Rental Considerations:

Applicant Vetting: Perform financial, reference, and background assessments.

Rent Control: No rent control measures for ADUs in Mountain View.

Security Deposits: Capped at one month’s rent for unfurnished and two for furnished units.

Animal Policy: The lease should delineate any pet-related limitations or fees.

Development Standards for Mountain View ADU

ADU Type Development Standards
Single-Family –   Detached or attached to the main house.

–   Minimum lot size depends on zoning (typically 3,500 sq ft or larger).

–   Maximum unit size: 1,200 sq ft.

–   Up to 2 bedrooms allowed.

Duplex –   Attached to a single-family home, sharing one wall.

–   Minimum lot size depends on zoning (typically 5,000 sq ft or larger).

–   Maximum unit size per dwelling: 800 sq ft.

–   Up to 1 bedroom per dwelling allowed.

Multi-family –   Contained within a larger multi-family building.

–   No minimum lot size requirement.

–   Maximum unit size depends on zoning regulations.

–   Multiple bedrooms allowed per unit.

Junior ADU (JADU) –   Located entirely within an existing single-family home.

–   No minimum lot size requirement.

–   Maximum unit size: 500 sq ft.

–   Efficiency kitchen with limited appliances (microwave, mini-fridge).

Mountain View Property Designations for ADU

  • Flood zones: Check if your property lies within a designated flood zone. Construction requirements and insurance costs may be affected.
  • Geohazard zones: Be aware of potential geotechnical risks like landslides or earthquakes in your area. Specific mitigation measures might be necessary for your ADU.
  • Easements: Identify easements on your property, granting access rights to utilities, public agencies, or neighbors. Building within easements might be restricted or require permission.

ADU Permit Requirements and Fees

Mountain View ADU Permit Requirements and Fees

Building Permit: All ADUs must comply with building codes and safety standards. The fees for ADU permits may vary depending on the size and complexity, ranging from $1,500 to $5,000 or more.

Planning Permit (Optional): Pre-review your ADU plans to ensure zoning and development standards compliance. Detached ADUs in specific zones are exempt. Fees for these ADUs vary, from as low as $500 to over $2,500.

School Impact Fees: May apply for larger projects based on square footage. Variable based on project size and location. Refer to the City of Mountain View Community Development Department for specific estimates.

Design Your Dream ADU Today!

With the rising popularity of ADUs in Mountain View, now is the ideal time to design your dream ADU! Whether for rental income, extra living space, or a home office, an ADU offers a versatile solution customized to your needs. Start your ADU construction today by calling us at +1-669-293-1126, and let us help you plan and build the perfect ADU for your property.



Navigating regulations for non-conforming lots can be tricky, but the City encourages creative solutions to maximize ADU opportunities. Consulting the Planning Division and exploring options like variances or conditional permits can increase approval chances.

ADU short-term rentals in Mountain View are uncertain due to evolving regulations. Platforms like Airbnb generally prohibit short-term rentals. Consider long-term leases for a simpler, compliant approach.

Absolutely! Mountain View actively supports renewable energy initiatives. Installing solar panels on your ADU can reduce your environmental footprint and potentially qualify you for financial incentives and rebates from the city and state.