Introduction
Mountain View has established comprehensive rules and regulations for Accessory Dwelling Units (ADUs) to promote responsible development while ensuring community standards. These regulations help maintain the city’s character, enhance property values, and provide additional housing options. ADU Specialist Bay Area can assist homeowners in navigating these regulations, ensuring that your ADU project meets all local requirements and is completed efficiently.
Essential ADU Rules for Mountain View
What you can build
Maximum size
ADUs in Mountain View can be up to 1,000 square feet.
Side / rear setbacks
A minimum of 4 feet is required for side and rear setbacks.
Two stories
Two-story ADUs are permitted, adhering to height limitations.
Building separation
A minimum of 6 feet separation is required between structures.
Permitting timeline
Standard
The standard permitting process takes approximately 60 days.
Coastal
Coastal zone permits may take up to 90 days for approval.
Zoning Regulations in Mountain View
Mountain View zoning regulations support ADU development in various residential zones, ensuring flexibility and adherence to community standards.
ADU Size Limitations
| Lot Size | Single-Family (Maximum Floor Area Allowed) | Duplex and Multi-Family (Maximum Floor Area Allowed) |
| Under 7000 | 700 sq ft | Not permitted |
| 7000 - 9999 | 800 sq ft | 1 ADU + 400 sq ft per existing unit (up to 1000 sq ft max) |
| 10000 - 12999 | 900 sq ft | 1 ADU + 450 sq ft per existing unit (up to 1000 sq ft max) |
| 13000 - 19999 | 1000 sq ft | 1 ADU + 500 sq ft per existing unit (up to 1000 sq ft max) |
| 20000+ | 1000 sq ft | 1 ADU + 550 sq ft per existing unit (up to 1000 sq ft max) |
ADU Height Limitations
Mountain View permits ADUs to be built up to 16 feet high, ensuring they blend with the surrounding residential architecture.
Building Coverage
Total building coverage for ADUs in Mountain View must not exceed 40% of the lot area.
Location
| Property Type | Location Requirement |
| Single-Family Homes | Attached ADUs: Side or rear of the primary residence. |
| Detached ADUs: Anywhere in the rear yard. | |
| Junior ADUs (JADUs): Within the existing primary dwelling. | |
| Duplex and Multifamily | Attached ADUs: Side or rear of the primary structure. |
| Detached ADUs: Rear yard only. |
Exterior details
Exterior designs of ADUs must match the primary residence in terms of color, materials, and architectural style to maintain neighborhood aesthetics.
Parking
Mountain View requires one additional parking space per ADU, except when located within half a mile of public transit.
Setbacks and buffer zones
Setbacks for ADUs in Mountain View include a minimum of 4 feet for side and rear yards, maintaining adequate space and privacy.
Minimum Lot Area
| Lot Size | Minimum Lot Area for ADU | Description |
| Under 7000 | ADUs not permitted | Smaller lots are not eligible for ADU construction. |
| 7000 - 9999 | 7000 sq ft | Suitable for standard ADU development. |
| 10000 - 12999 | 10000 sq ft | Adequate for both attached and detached ADUs. |
| 13000 - 19999 | 13000 sq ft | Supports larger or multiple ADUs. |
| 20000+ | No minimum lot area requirement | Flexible for expansive ADU projects. |
Connection for utilities
ADUs in Mountain View must be connected to the primary residence’s utilities, including water, sewer, and electricity, ensuring seamless integration.
Fire safety
ADUs must comply with local fire safety regulations, including the installation of smoke detectors, fire extinguishers, and accessible escape routes.
Room specifications
- Sleeping Areas: Must include egress windows and a minimum ceiling height of 7 feet.
- Kitchen: Requires a sink, stove, and refrigerator, with adequate counter space.
- Bathroom: Must have a toilet, sink, and shower or bathtub, adhering to plumbing codes.
- Storage: Provide at least 50 cubic feet of storage space within the ADU.
Short-term Rentals and Home Occupations Regulations
Short-term rentals of ADUs are restricted in Mountain View, and home occupations must comply with local zoning laws.
Building Codes
ADUs must meet the latest building codes, including structural, electrical, and plumbing standards to ensure safety and durability.
Mountain View ADU Permit Guidelines
| Permit Type | Description | Estimated Fee |
| Building Permit | Required for ADU construction. | $2500 - $5000 |
| Electrical Permit | Necessary for electrical systems. | $400 - $700 |
| Plumbing Permit | Needed for plumbing installations. | $400 - $700 |
| Mechanical Permit | Required for HVAC systems. | $400 - $700 |
| Grading Permit | For site preparation and grading work. | $300 - $500 |
| Site Development Permit | Needed for overall site development. | $300 - $500 |
| Zoning Permit | Ensures compliance with local zoning laws. | $200 - $400 |
Property requirements
ADUs in Mountain View must comply with specific property requirements, including size, setbacks, and design standards.
Parking
Adequate parking must be provided, with one additional space required for the ADU.
Front setbacks
Front setbacks must be a minimum of 15 feet to ensure sufficient distance from the street.
Side and rear setbacks
Side and rear setbacks must be at least 4 feet to maintain privacy and space between structures.
Open space and rear yards
ADUs must not occupy more than 50% of the rear yard, preserving open space for residents.
Properties that qualify
To determine your property’s eligibility for ADU development, contact the Mountain View Planning Department.
- Verify that your property is within Mountain View’s jurisdiction.
- Check the specific residential zones that permit ADUs. Common zones in Mountain View include R-1, R-2, and R-M.
- Other General Plan designations that permit ADUs:
- Residential Mixed-Use (RMU): Allows ADUs in mixed residential and commercial areas, enhancing flexibility.
- Transit-Oriented Development (TOD): Encourages ADUs near public transit to reduce car dependency.
- Specific Plan areas: Designated areas with tailored regulations supporting ADU development.
Development standards
Single-family
- Attached: Must be located at the side or rear of the primary residence.
- Detached: Should be situated in the rear yard, adhering to setback requirements.
Duplex properties
- Attached: Can be added to the side or rear of existing structures.
- Detached: Must be placed in the rear yard, following local guidelines.
Multifamily properties
- Attached: Permitted on the side or rear, subject to zoning regulations.
- Detached: Located in the rear yard, ensuring adequate separation from other units.
Junior ADUs (JADUs)
JADUs must be within the primary dwelling, offering a smaller, more integrated housing option.
Property designations
- Flood Zones: ADUs in flood zones must meet elevation and flood-proofing standards to prevent water damage.
- Geohazard Zones: ADUs in geohazard zones require additional safety measures to mitigate risks.
- Historic Designation: ADUs on historically designated properties must preserve architectural integrity.
- Easements: Construction must respect utility and access easements to avoid legal and functional issues.
Summary
Mountain View’s ADU regulations provide clear guidelines for homeowners looking to add accessory units to their properties. These rules ensure that ADUs are built safely, sustainably, and in harmony with the community’s character. By partnering with ADU Specialist Bay Area, homeowners can navigate these regulations efficiently and successfully complete their ADU projects, adding value and versatility to their properties.
FAQ
ADUs in Mountain View must adhere to a maximum height limit of 16 feet to ensure they are compatible with the surrounding neighborhood.
Yes, Mountain View allows one ADU per single-family lot and multiple ADUs on multifamily lots, depending on the lot size and zoning regulations.
Contact the Mountain View Planning Department to verify if your property falls within the eligible zones for ADU development and meets all necessary criteria.
The minimum lot size required varies; lots under 7000 square feet are not permitted for ADUs, while larger lots have specific area requirements.
Yes, ADUs must match the primary residence in terms of exterior materials, colors, and architectural style to maintain neighborhood aesthetics.
ADUs must maintain a minimum of 4 feet for side and rear setbacks to ensure adequate space and privacy between structures.
Two-story ADUs are permitted in Mountain View, provided they adhere to the height limitations and other relevant regulations.
Yes, Mountain View typically requires one additional parking space for ADUs, except when located within half a mile of public transit.
Permitting fees vary, with building permits ranging from $2500 to $5000 and additional fees for electrical, plumbing, and mechanical permits.
Yes, short-term rentals are restricted to ensure that ADUs provide long-term housing solutions rather than transient accommodations.
ADUs must be connected to the primary residence’s utilities, including water, sewer, and electricity, ensuring they are fully integrated with the main home.
Yes, ADUs must comply with all local fire safety regulations, including the installation of smoke detectors, fire extinguishers, and accessible escape routes.
Yes, JADUs are permitted within the primary dwelling, offering a smaller, more integrated housing option that adheres to specific size and configuration requirements.
Exterior designs of ADUs must complement the primary residence in terms of materials, colors, and architectural style to ensure consistency within the neighborhood.
Yes, ADUs in historic districts must preserve the architectural integrity of the primary residence and comply with additional review processes to ensure compatibility with the historic character.
ADUs must not occupy more than 50% of the rear yard to preserve open space and provide adequate outdoor areas for residents.
ADUs on multifamily properties must be placed in the rear yard and adhere to specific setback and location requirements to ensure proper spacing and privacy.
ADUs in geohazard zones must implement additional safety measures to mitigate risks, such as enhanced structural support and site-specific engineering solutions.
The grading permit process involves submitting plans that detail site preparation and grading work, with fees typically ranging from $300 to $500.
Yes, but ADUs in flood zones must meet elevation and flood-proofing standards to ensure they are protected from potential water damage.
ADUs on duplex properties must maintain a minimum of 4 feet for side and rear setbacks, ensuring adequate separation from adjacent structures.
TOD areas encourage ADU development near public transit to reduce car dependency, with specific designations and guidelines to support this goal.
For properties over 20000 square feet, there is no minimum lot area requirement, providing flexibility for expansive ADU projects.
Yes, ADUs must meet all applicable building codes, including structural, electrical, and plumbing standards to ensure safety and compliance.
ADU Specialist Bay Area offers comprehensive support, including navigating local regulations, obtaining permits, and ensuring that your ADU project is completed efficiently and in compliance with Mountain View’s standards.
