Atherton ADUs Explained: From Zoning to Completion

Accessory Dwelling Units (ADUs) are quickly becoming a key feature in the landscape of urban and suburban housing, particularly in affluent communities like Atherton, California. These self-contained residential units, often located on the same property as a single-family home, offer a unique solution to housing shortages while maintaining neighborhood character. Whether you're a homeowner considering adding an ADU, or simply curious about the process, this article will guide you through every phase of building an ADU in Atherton—from zoning laws to construction completion.

What Is an Atherton ADU?

An Accessory Dwelling Unit (ADU) is a smaller, secondary living space located on the same parcel of land as a primary residence. Typically, these units include living areas, kitchens, bathrooms, and bedrooms, and can range from small studios to full two-bedroom units. In Atherton, as in many parts of California, ADUs are viewed as a sustainable and efficient way to address growing housing demand, especially in high-cost areas.

ADUs come in several forms:

• Detached ADUs: Separate buildings on the same property, often in the backyard.
• Attached ADUs: Units that are part of the primary residence, such as above a garage or an extension of the home.
• Garage Conversions: An existing garage space converted into a habitable living unit.
• Junior ADUs: A smaller unit, typically within a single-family home, often taking the place of a bedroom or a part of the home’s basement.

In Atherton, these units not only provide opportunities for multigenerational living but can also serve as rental properties, guest homes, or home offices, offering residents more flexibility.

Why Build an ADU in Atherton?

There are several reasons why homeowners in Atherton may consider building an ADU on their property.

1. Rental Income

Given Atherton's affluent nature, there is high demand for rental properties, particularly in Silicon Valley. Homeowners can rent out an ADU to generate additional income, whether to long-term tenants or short-term through platforms like Airbnb.

2. Housing Affordability

With high housing prices in Atherton, an ADU offers a more affordable housing option, especially for young professionals, students, or retirees who may not be able to afford the area’s steep home prices. By creating additional rental units, homeowners can help alleviate the regional housing shortage.

3. Multigenerational Living

Many families choose to build ADUs as a way to provide housing for elderly relatives or adult children while still maintaining privacy. An ADU offers independence while allowing families to stay connected and offer care when needed.

4. Increase Property Value

A well-designed ADU can add significant value to a home. According to various real estate experts, adding an ADU can increase a property's value by as much as 20-30%. The additional living space, whether for rental or personal use, makes the property more attractive to potential buyers.

5. Flexibility of Use

ADUs offer immense flexibility. Beyond serving as a rental space or home for family members, they can also serve as a home office, studio, or workshop. The possibility of converting the unit for different purposes adds to its long-term value and usefulness.

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Zoning Laws and Regulations for Atherton ADUs

Before breaking ground on an ADU, it is crucial to understand the local zoning laws and regulations. In Atherton, as with other cities in California, ADUs are regulated by both state and local laws. These laws have evolved in recent years, particularly with the state’s push to address the housing crisis.

State Laws Governing ADUs in California

In 2017, California passed a series of laws aimed at making it easier to build ADUs throughout the state. These laws included:

• Relaxed Parking Requirements: If an ADU is within half a mile of public transit, parking requirements may be waived.
• Streamlined Permitting: ADU permits must be processed more quickly, usually within 60 days, to make the process more efficient.
• Reduced Fees: Local governments are prohibited from imposing excessive fees on ADUs, although some fees like water and sewer connections may still apply.
• Size Limits: ADUs must generally be no larger than 1,200 sq. ft., although some localities allow smaller units for efficiency.

Atherton-Specific ADU Regulations

Atherton, while following state guidelines, also has specific local zoning laws that must be adhered to. Here are some key regulations:

1. Lot Size: Atherton requires a minimum lot size for ADUs, typically around 7,500 square feet. If your lot is smaller than this, building an ADU may not be possible.
2. ADU Size: The size of the ADU is regulated based on the type of unit. Detached ADUs can be up to 1,200 square feet, while attached units or garage conversions may have slightly smaller size limits.
3. Setbacks: Setback requirements (the distance an ADU must be set back from the property line) typically apply. In Atherton, setbacks may be stricter than in other areas, so it's essential to check local zoning codes before proceeding.
4. Height Restrictions: ADUs in Atherton cannot exceed a certain height limit. For example, the height of a detached ADU is generally limited to 16 feet, while other structures like garages may have additional restrictions.
5. Design Review: Atherton is known for its emphasis on aesthetics, especially in residential areas. Your ADU design may need to be reviewed for compatibility with the architectural style of your existing home and neighborhood.
6. Parking: While California has relaxed parking requirements for ADUs, Atherton may still require parking if the ADU is a certain size or located far from public transportation.

How to Begin the ADU Process in Atherton

Building an ADU is an involved process that requires careful planning. Here’s an overview of the key steps involved.

1. Planning and Design

The first step in creating an ADU is to work with an architect or designer who is familiar with local regulations. They can help ensure your design fits within zoning and building code requirements. You'll need to decide on the type of ADU—whether it will be attached to your house, a standalone unit in your backyard, or a conversion of an existing structure like a garage.

Factors to consider in the planning phase include:

• Site Evaluation: An evaluation of your lot will help determine if an ADU is feasible, especially considering setbacks, utilities, and available space.
• Utility Access: An ADU will need access to utilities such as water, sewer, and electricity. If your property lacks these services in the area of the ADU, you may need to plan for additional infrastructure.
• Design: The design should take into account privacy, access, and aesthetics. You want the ADU to blend well with your primary residence and the surrounding community.

2. Permitting

After finalizing the design, the next step is to apply for permits. Atherton's planning department will need to review your ADU plans. The permitting process includes:

• Building Permit: For construction to begin, a building permit is required, which ensures the structure meets safety and building codes.
• Planning Permit: Depending on your ADU's location and design, you may also need a planning permit to confirm compliance with zoning laws.
• Inspections: Throughout the construction process, several inspections may be necessary to ensure the unit complies with health, safety, and building codes.

3. Construction

Once permits are in hand, the construction of the ADU can begin. The timeline for construction will vary depending on the complexity of the project, with simpler garage conversions taking less time than completely new structures. The construction phase will typically include:

• Site Preparation: Clearing the site and preparing it for foundation work.
• Foundation and Framing: Laying the foundation and framing the structure.
• Electrical and Plumbing: Installing essential systems like plumbing and electrical wiring.
• Finishing Touches: Installing fixtures, painting, and completing interior details.

4. Completion and Occupancy

After construction is complete, a final inspection will be conducted. If all requirements are met, you’ll receive a Certificate of Occupancy, which legally allows the ADU to be used as a residential space. At this point, you can begin renting the unit, using it for family, or transforming it into a home office.

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ADU Financing Options

Building an ADU is a significant investment. While some homeowners in Atherton may have the capital to finance their project outright, others may need to consider various financing options.

1. Home Equity Line of Credit (HELOC): If you have significant equity in your home, you may be able to finance the ADU construction through a HELOC, which offers flexibility and relatively low-interest rates.
2. Cash-Out Refinance: This option involves refinancing your existing mortgage to extract some of the equity in your home to fund the ADU construction.
3. Construction Loans: Construction loans are short-term loans specifically designed to fund home building projects. These loans often transition into a traditional mortgage once the construction is complete.
4. Personal Loans: If you have good credit, personal loans are an option for financing smaller projects. However, personal loans typically come with higher interest rates than home equity products.

Summary

Building an ADU in Atherton is a practical and rewarding investment for homeowners. Not only do they provide a potential source of rental income or space for family members, but they also increase property value and contribute to solving the housing crisis. However, navigating the zoning laws, permitting process, and construction phase requires careful planning, a solid understanding of local regulations, and the right financial strategy.

With the right team of professionals and a well-thought-out plan, your ADU in Atherton can be a beautiful and functional addition to your property. Whether you're looking to build for rental income, multigenerational living, or simply to maximize your property's potential, the process of creating an ADU can lead to significant long-term benefits.

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