Introduction
San Carlos, known as the “City of Good Living,” offers a welcoming environment for the development of Accessory Dwelling Units (ADUs). The city’s regulations aim to facilitate the creation of ADUs while maintaining the charm and character of its neighborhoods. These units provide valuable additional housing options, promoting sustainable and diverse living arrangements within the city. San Carlos’ supportive framework for ADU development ensures that homeowners can seamlessly integrate these units into their properties, contributing to the community’s housing needs. For expert assistance with ADU development in San Carlos, ‘ADU Specialist Bay Area’ is ready to help.
Essential ADU Rules for San Carlos
What you can build
Maximum size
1,200 sq ft for detached ADUs.
Side / rear setbacks
5 feet for both side and rear.
Two stories
Permitted with height restrictions.
Building separation
Minimum 6 feet from other structures.
Permitting timeline
Standard
Approximately 60 days.
Coastal
Not applicable.
Zoning Regulations in San Carlos
San Carlos’ zoning regulations ensure that ADUs are compatible with the existing residential areas. ADUs are permitted in most residential zones, fostering diverse and sustainable housing solutions.
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
Detached ADUs can be up to 16 feet in height, with potential for two stories if certain conditions are met.
Building Coverage
The total building coverage for an ADU must not exceed 45% of the lot area.
Location
| Property Type | Location Requirement |
| Single-Family Homes | Attached ADUs: Must connect to the primary residence. |
| Detached ADUs: Located behind the primary residence. | |
| Junior ADUs (JADUs): Must be within the primary residence. | |
| Duplex and Multifamily | Attached ADUs: Allowed within existing structures. |
| Detached ADUs: Must be located behind primary structures. |
Exterior details
ADUs in San Carlos must match the primary dwelling in architectural style, materials, and roof design to maintain aesthetic consistency.
Parking
One off-street parking space is required per ADU, with flexibility for tandem parking on an existing driveway.
Setbacks and buffer zones
ADUs must maintain a minimum 5-foot side and rear setback, providing sufficient space and privacy between properties.
Minimum Lot Area
| Lot Size | Minimum Lot Area for ADU | Description |
| Under 7000 | ADUs not permitted | Small lot restriction |
| 7000 - 9999 | 7000 sq ft | Adequate space |
| 10000 - 12999 | 10000 sq ft | Larger lot |
| 13000 - 19999 | 13000 sq ft | Spacious lot |
| 20000+ | No minimum lot area requirement | Ample space |
Connection for utilities
ADUs must be equipped with independent utility connections, including water, sewer, and electricity, to ensure they function as standalone units.
Fire safety
Compliance with local fire safety regulations is mandatory, ensuring ADUs are equipped with necessary fire safety measures such as smoke detectors and fire extinguishers.
Room specifications
- Sleeping Areas: Must include at least one bedroom with proper egress and ventilation.
- Kitchen: Must have a functional kitchen with essential appliances like a sink, stove, and refrigerator.
- Bathroom: Must include a toilet, sink, and bathing facilities to meet basic living requirements.
- Storage: Adequate storage space, such as closets and cabinets, must be provided.
Short-term Rentals and Home Occupations Regulations
ADUs cannot be used for short-term rentals (less than 30 days) and must comply with local regulations if used for home-based businesses.
Building Codes
ADUs must adhere to all applicable local building codes, covering structural integrity, electrical systems, plumbing, and mechanical standards.
San Carlos ADU Permit Guidelines
| Permit Type | Description | Estimated Fee |
| Building Permit | Required for ADU construction. | $2500 - $5000 |
| Electrical Permit | Required for new electrical systems. | $400 - $700 |
| Plumbing Permit | Required for new plumbing installations. | $400 - $700 |
| Mechanical Permit | Required for HVAC systems. | $400 - $700 |
| Grading Permit | Required if grading is necessary. | $300 - $500 |
| Site Development Permit | Required for site planning. | $300 - $500 |
| Zoning Permit | Required for zoning compliance. | $200 - $400 |
Property Requirements
ADUs in San Carlos must meet specific property requirements to ensure they are suitable and harmonious additions to the neighborhood.
Parking
One off-street parking space is required per ADU, providing convenient and accessible parking solutions.
Front setbacks
ADUs must maintain the same front setback as the primary residence to ensure consistency with the streetscape.
Side and rear setbacks
A minimum of 5 feet is required for side and rear setbacks to ensure adequate separation from property lines and neighboring structures.
Open space and rear yards
ADUs must leave at least 10% of the lot area as open space, ensuring sufficient outdoor space for residents.
Properties That Qualify
To determine your property’s eligibility for ADU development, contact the San Carlos Planning Department.
- Verify that your property is within San Carlos’ jurisdiction.
- Check the specific residential zones that permit ADUs. Common zones in San Carlos include R-1, R-2, and R-M.
- Other General Plan designations that permit ADUs:
- Residential Mixed-Use (RMU): ADUs are allowed in RMU zones, supporting a blend of residential and commercial uses.
- Transit-Oriented Development (TOD): ADUs are encouraged in TOD areas to promote the use of public transit and reduce reliance on cars.
- Specific Plan areas: ADUs are permitted in designated specific plan areas, supporting strategic planning initiatives.
Development standards
Single-family
- Attached: Must share a wall with the primary residence and maintain design consistency.
- Detached: Must be located behind the primary residence, with a maximum size of 1,200 sq ft.
Duplex properties
- Attached: Can be integrated into existing duplex structures, maintaining architectural harmony.
- Detached: Must be located behind existing duplex units, with a maximum size of 1,200 sq ft.
Multifamily properties
- Attached: Allowed within existing multifamily structures, adhering to design standards.
- Detached: Must be located behind primary multifamily buildings, with a maximum size of 1,200 sq ft.
Junior ADUs (JADUs)
Must be within the primary residence and share some facilities, such as a bathroom, with the main dwelling.
Property designations
- Flood Zones: ADUs in flood zones must comply with elevation and drainage requirements to mitigate flood risks.
- Geohazard Zones: ADUs in geohazard areas must adhere to regulations ensuring safety and stability.
- Historic Designation: ADUs in historic districts must preserve the architectural integrity and character of the neighborhood.
- Easements: ADUs must respect existing easements, ensuring access for utilities and maintenance.
Summary
San Carlos provides a supportive regulatory framework for ADU development, promoting diverse and sustainable housing options. By adhering to specific guidelines on size, design, and location, homeowners can contribute to the community’s housing needs while preserving the city’s charm. For those interested in developing an ADU in San Carlos, ‘ADU Specialist Bay Area’ offers expert guidance to streamline the process and ensure compliance.
FAQ
Setbacks for ADUs in San Carlos generally require a minimum of 5 feet for both side and rear property lines, ensuring adequate space and privacy.
ADUs must have separate utility connections for water, sewer, and electricity to ensure they operate independently.
Adding an ADU typically results in an increase in property taxes based on the added value of the new unit.
One off-street parking space is required per ADU, which can be tandem parking on an existing driveway to optimize space.
ADUs must comply with all local building codes, including structural, electrical, plumbing, and mechanical standards, to ensure safety and functionality.
ADUs must match the primary dwelling in design, materials, and roof pitch to maintain neighborhood aesthetics and cohesion.
Zoning regulations dictate where ADUs can be built, including specific residential zones like R-1, R-2, and R-M, ensuring compatibility with existing neighborhoods.
The maximum size for ADUs varies by lot size, with a general maximum of 1,200 sq ft, ensuring they fit well within residential areas.
Adding an ADU may increase property insurance premiums due to the additional structure and potential risks associated with it.
ADUs must meet energy efficiency standards, incorporating proper insulation, energy-efficient windows, and appliances to reduce energy consumption and costs.
ADUs must adhere to local noise regulations to minimize disturbances to neighbors and maintain a peaceful living environment.
Permit costs for ADUs in San Carlos range from $200 to $5,000, depending on the type of permit required for the construction and development process.
ADUs must comply with local occupancy standards, typically limiting the number of occupants based on the unit’s size and ensuring adequate living conditions.
Fire safety measures for ADUs include installing smoke detectors, fire extinguishers, and ensuring proper egress routes to protect occupants in case of emergencies.
ADUs in San Carlos cannot be used for short-term rentals (less than 30 days), ensuring they contribute to long-term housing availability and community stability.
Landscaping for ADUs should enhance the overall property appearance, using plants and designs that complement the primary residence and neighborhood aesthetics.
In historic districts, ADUs must be designed to preserve the neighborhood’s architectural integrity, adhering to guidelines set by the Historic Preservation Commission to maintain the area’s character.
Designing ADUs with privacy in mind includes strategic placement of windows and maintaining adequate setbacks to minimize intrusions and ensure a comfortable living environment for all residents.
ADUs must have appropriate waste management systems, providing access to trash, recycling, and compost bins in compliance with local regulations to ensure proper waste disposal and environmental sustainability.
ADUs typically receive separate addresses and mail delivery services to ensure clear identification and efficient postal service, contributing to the unit’s independent functionality and convenience for occupants.
