Stanford ADU Zoning and Building Standards
With California’s recent ADU-friendly legislation and Stanford’s supportive regulations, now’s the perfect time to unlock the potential of your property! Building an ADU can provide valuable living space for families, generate rental income, or create a comfortable guest retreat.
But before you break ground, it’s important to understand Stanford’s specific ADU regulations. This guide will equip you with the knowledge to navigate the process smoothly and ensure your ADU adheres to all local requirements.
Property Requirements
Building Size
- Single-Family Zoned Lots: Imagine a classic suburban neighborhood with detached houses on individual lots. That’s a single-family zone! Here, you’re generally golden to build an ADU up to 800 square feet, with a minimum of 150 square feet. Think cozy studio apartment or a comfortable in-law suite.
- Duplex Family Zoned Lots:Picture two attached houses sharing a wall on a single lot. That’s a duplex zone! For these, Stanford allows two types of ADUs:
- Attached ADUs: These can be built directly onto your existing duplex and can be up to 500 square feet, making them ideal for a small guest room or home office.
- Detached ADUs: Think of a separate cottage in your backyard! These can also reach 800 square feet, offering more spacious options like a two-bedroom unit.
- Multi-Family Zoned Lots: Envision apartment buildings or larger complexes with multiple dwelling units. That’s a multi-family zone! Here, ADU options get even more interesting:
- Conversion ADUs: Breathe new life into unused spaces within your existing multi-family building! Converted ADUs can be up to 800 square feet and are perfect for transforming old storage rooms or common areas.
- New Construction ADUs: Want to add a whole new unit to your multi-family property? Detached new construction ADUs are allowed, with a maximum size of 800 square feet and a minimum of 150 square feet. This opens doors for creating dedicated rental units or even small apartment-style living spaces.
Owner-occupancy
Although California law allows ADUs to be rented out, Stanford has a special rule. Between January 2020 and December 2024, the owner must occupy newly built ADUs in the primary residence or the ADU itself. You can’t make an ADU and immediately rent it out – you’ll need to live in one of the units for the first three years.
Number of Units Allowed
In Stanford, you can typically build one ADU per single-family zoned lot. It can be attached or detached depending on your preference and property layout. Duplex-zoned lots allow for an additional unit: an attached ADU with a maximum size of 500 square feet. Multi-family zones provide flexibility, allowing the conversion of ADUs within existing buildings and new construction ADUs as separate units, both capped at 800 square feet.
Stanford Building Height
- Single-Family: Your ADU can’t be taller than that! 16 feet is the maximum height for detached and attached units, ensuring harmony with the surrounding neighborhood.
- Duplex Family: Here, things get a little more interesting. Detached ADUs can still reach 16 feet, but attached ones can stretch up to 25 feet. Think bonus room or even a small rooftop terrace!
- Multi-Family: there are no height restrictions for Conversion ADUs within existing structures, allowing creative use of vertical space, whereas, for New Construction ADUs in backyards, the height limit is 16 feet, mirroring regulations in single-family zones.
Stanford Building Size
- Single-Family: Cozy ADUs can be your perfect studio apartment or in-law suite, ranging from a minimum of 150 sq ft to a maximum of 800 sq ft.
- Duplex Family: Two houses sharing a wall offer attached or detached ADUs options. Attached ADUs, up to 500 sq ft, are great for guest rooms or home offices. Detached ADUs, up to 800 sq ft, provide spacious two-bedroom possibilities.
- Multi-Family: Zone offers flexible options for Conversion ADUs with no size limit. New Construction ADUs have a maximum limit of 800 sq ft, ensuring comfortable living with a minimum requirement of 150 sq ft.
Fire Safety Regulations
Stanford requires smoke detectors and carbon monoxide alarms in all ADUs, just like the main dwelling. Sprinklers are not mandatory in new ADUs unless needed for the primary residence, but always consider additional safety measures like fire extinguishers and escape routes for peace of mind.
Parking
Generally, one space per ADU bedroom is required unless you’re within 0.5 miles of public transit, then, it’s a bonus free pass! But always double-check your zone specifics, as some duplex ADUs have different rules.
Utility Connections
New ADUs usually need separate water, sewer, and electricity connections, ensuring smooth operation and fair billing. For gas and cable/internet, sharing with the main dwelling might be okay, but check with the Planning Division to be sure.
Setbacks
You’ll need to keep your ADU at least 4 feet from the side and rear property lines and 10 feet from the front yard. Corner lots might have additional restrictions, so always check with the City of Stanford Planning Division for the exact requirements on your property.
Zoning Regulations
Single Family
Offer classic suburban living with detached houses on individual lots. Think picket fences and quiet streets. Building your ADU here? Keep it cozy and contained, with a maximum size of 800 square feet and a minimum of 150 square feet.
Duplex Family
ADU options are like choosing your favorite ice cream flavor: attached units up to 500 sq ft for a bonus room or home office or a spacious detached ADU of 800 sq ft, perfect for a two-bedroom haven.
Multi-Family
Unleash your inner architect: convert unused areas within existing buildings (size doesn’t matter!) or build a separate ADU in your backyard, both capped at 800 sq ft. Remember, Multi-Family zones offer the most ADU freedom.
RF Zone Minimum Lot Area in Stanford
Stanford’s RF Zones establish minimum lot area requirements for Accessory Dwelling Unit (ADU) construction, ensuring adequate space and preserving neighborhood character.
- RF-20: 5,000 sq ft. This zone is intended for single-family homes on large lots.
- RF-30: 7,500 sq ft. This zone is similar to RF-20 but allows for slightly larger homes.
- RF-40: 10,000 sq ft. This zone is intended for even larger or smaller homes with accessory dwelling units (ADUs).
- RF-50: 12,500 sq ft. This zone is similar to RF-40 but allows for even larger homes or more ADUs.
- RF-60: 15,000 sq ft. This zone is intended for the largest homes in Stanford or multiple dwellings on a single lot.
- RF-75: 18,750 sq ft. This zone is similar to RF-60 but allows for even larger homes or more ADUs.
- RF-100: 25,000 sq ft. This zone is the largest residential zone in Stanford, and it is intended for very large homes or estates.
Room Specifications
| Room Type | Specifications |
| Bathroom | – Minimum area: 35 sq ft (including fixtures) – Minimum toilet width: 24 in – Minimum shower stall size: 36 in x 36 in – Grab bars in shower and tub/shower combination required – Ventilation required |
| Kitchen | – Minimum countertop length: 4 ft – Minimum sink size: 24 in x 18 in – Refrigerator, stovetop, and oven required (unless kitchenette) – Adequate ventilation required |
| Sleeping Areas | – Minimum ceiling height: 7 ft – Minimum floor area: 70 sq ft per occupant (excluding closets) – Closet space required (minimum 10 sq ft) – Adequate natural light and ventilation recommended |
| Storage | – Minimum 5% of total ADU floor area dedicated to storage – Built-in storage solutions recommended (e.g., cabinets, shelves) |
Location Requirements
- Detached ADU: These stand alone in your backyard, offering spacious options like two-bedroom units and even small cottages (up to 800 sq ft). Think private entrance, potential rental income, and your little oasis.
- Attached ADU: provides convenient access and bonus space. They come in two sizes: cozy guest rooms or home offices up to 500 sq ft in duplex zones or spacious 800 sq ft units in single-family zones. Think in-law suites, extra workspace, or a closer family connection.
- JADU (Junior Accessory Dwelling Unit): JADUs are tiny titans tucked within existing garages or converted spaces. They max out at 220 sq ft and are perfect for a comfortable studio or home office. Think of efficient living, maximizing space within your existing structure.
Rental Requirements
- Owner-Occupancy: Between January 2020 and December 2024, the owner must occupy newly built ADUs for three years (either in the main house or the ADU itself).
- Permits and Inspections: Obtain all necessary permits and pass inspections before renting your ADU. Expect fees ranging from $100 to $500 depending on the permit type and complexity.
- Business License: If you intend to rent your ADU for more than 30 days per year, you’ll need a business license from the City of Stanford. Costs around $50.
- Tenant Screening: Conduct thorough background checks and credit checks on potential tenants. Expect fees of around $25-$50 per applicant.
Development Standards for Stanford ADU
| ADU Types | Development Standards Specification |
| Single-family | – Max size: 800 sq ft, min size: 150 sq ft – Generally detached, attached allowed in some cases – 4 ft setbacks from side and rear property lines – 10 ft setback from front yard (may vary for corner lots) |
| Duplex | – Attached ADU: max size 500 sq ft – Detached ADU: max size 800 sq ft, min size 150 sq ft – Same setbacks as single-family for detached ADUs – Attached ADUs follow shared wall requirements |
| Multi-family | – Conversion ADUs: no size limit within existing buildings – New construction ADUs: max size 800 sq ft, min size 150 sq ft – 4 ft setbacks from all property lines |
| Junior ADUs (JADUs) | – Max size 500 sq ft – Must be contained within an existing single-family dwelling – Can share a bathroom with main dwelling, separate kitchen required – No minimum size or setback requirements |
Stanford Property Designations for ADU
- Flood zones: Stanford maps areas at risk of flooding. Building an ADU in a designated flood zone might be restricted or require specific floodproofing measures.
- Geohazard zones: Stanford identifies areas prone to landslides, earthquakes, or other geological hazards. Building an ADU in such zones requires additional engineering and special permits.
- Easements: Designated areas where others have rights, like access to utilities or public infrastructure. Building your ADU within an easement might be prohibited or require specific approvals.
ADU Permit Requirements and Fees
- Building Permit: This is the big one, covering construction plans, materials, and adherence to building codes. Expect fees ranging from $1,000 to $5,000 depending on ADU size and complexity.
- Electrical Permit: Ensures safe electrical wiring and compliance with regulations. Costs around $100 to $500.
- Plumbing Permit: Guarantees proper plumbing installation and adherence to codes. Fees typically range from $100 to $300.
- Mechanical Permit: If your ADU includes HVAC systems, this permit ensures their safe and efficient operation. Costs vary based on system complexity but are typically around $100 to $200.
- Plan Review Fees: The City of Stanford reviews your ADU plans for compliance, incurring fees of around $200 to $500.
- Inspections: Several inspections occur throughout the construction process, with fees ranging from $50 to $150 per visit.
