Can You Build an ADU Before the Main House in California? – Regulations Explained

Last updated on April 14, 2024

In California, you generally cannot build an ADU before the main house; ADUs are intended as secondary dwellings on a lot with an existing single-family home.

Key takeaways:

  • ADUs are typically built after the main house in California.
  • Eligibility criteria vary and require detailed plans for both ADU and main residence.
  • Local ordinances and zoning requirements can impact the sequencing of construction.
  • Recent legislation allows for ADUs to be built before the main house.
  • Case studies demonstrate the flexibility and benefits of building an ADU first.
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Eligibility Criteria for ADU Construction Prior to Main Residence

eligibility criteria for adu construction prior to main residence

In California, constructing an ADU before the primary residence is subject to specific rules. Traditional zoning laws prioritize the establishment of a main house first, but with changing legislation, flexibility is growing.

To build an ADU on a vacant lot, one must navigate both state law and local ordinances. California state law, which is designed to encourage the proliferation of ADUs, gives local jurisdictions the power to develop their own regulations within the state framework. While state law does not explicitly prohibit an ADU from being the first structure on a property, most local ordinances have been written with the assumption that a primary dwelling exists or will be constructed concurrently.

For eligibility, a property owner must submit detailed plans for both the ADU and the future main residence when seeking permits. Local planning departments review these plans to ensure compliance with zoning, safety, and environmental standards. Moreover, the intended use of the ADU during the period before the main house’s construction is subject to scrutiny, particularly regarding utilities and access roads.

It’s also important to consider the lot size and setback requirements, which vary widely between jurisdictions and might affect the feasibility of erecting an ADU first. Additionally, some areas may impose owner-occupancy requirements, though recent state laws have relaxed these rules temporarily until 2025.

Before embarking on this route, consulting with local authorities is essential; they can offer up-to-date guidance on the feasibility of your project and any conditions that need to be met. Although the state encourages ADUs, the process is still firmly rooted in local control, and understanding specific municipal codes is crucial to a successful build.

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Understanding California’s Current ADU Legislation

California’s ADU laws exist to address housing shortages by facilitating the creation of additional living spaces. These laws operate within a framework that emphasizes flexibility and accessibility, allowing many homeowners to add ADUs on their properties. Here’s what shapes the legal environment:

– Statewide Standards: Regardless of local policies, California enforces minimum standards that effectively streamline ADU development, granting a consistent baseline for construction across different jurisdictions.

– Permits and Processes: The legislation mandates that local governments must provide a permitting process for ADUs that is fair, efficient, and not overly burdensome.

– Owner Occupancy: Recent changes have lifted the owner-occupancy requirement for ADUs built between 2020 and 2025, meaning that the property owner is not required to live in either the primary or accessory dwelling unit during this time frame.

– Lot Size and Zoning: While many localities had strict zoning rules, California’s laws now override some of these, allowing ADUs on lots zoned for single-family and multifamily use, which has been an essential change in increasing housing supply.

– Parking and Setbacks: New ADUs are exempt from certain parking requirements that often hindered their development, and setbacks are typically reduced, simplifying the placement of new structures on existing lots.

These points serve as a compass guiding the construction of ADUs before the main residence. However, success in this endeavor still relies on navigating local adaptations of these state standards.

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The Role of Local Ordinances in ADU and Main House Sequencing

While state laws provide the overarching framework for ADU development, local ordinances can significantly influence the sequencing of construction. Cities and counties have some discretion to adopt regulations that shape local development. Here’s how these ordinances can shape the possibilities:

  1. Zoning Requirements: Local zoning codes may have specific conditions regarding lot size and density that impact the ability to build an ADU before the main residence.
  1. Permitting Process: Municipalities may establish their own permitting procedures, which could either streamline or complicate the process of constructing an ADU first.
  1. Development Standards: Local development standards may dictate minimum requirements for the main residence, influencing whether an ADU can be the initial structure on a property.
  1. Utilities and Infrastructure: Provisions related to infrastructure hookup and access can affect the viability of building an ADU in advance, as some jurisdictions might require the primary structure to establish utility connections.
  1. Historical or Coastal Areas: In areas with special designations, such as historic districts or coastal zones, additional regulations or approvals might be necessary, potentially affecting construction order.

It’s crucial for homeowners to engage with local planning departments early in the process to understand the unique regulatory landscape of their community and assess the feasibility of their construction plans.

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Assessing the Impact of Senate Bill 9 On ADUs As Primary Dwellings

Senate Bill 9, a recent update to California’s housing legislation, has made waves by enabling the subdivision of residential lots to create more housing opportunities. Traditionally, accessory dwelling units (ADUs) serve as secondary homes on a property with an existing primary residence. However, SB 9 opens the door for homeowners to potentially prioritize the construction of an ADU, even before the main house is built.

Key points to understand in this context include:

  • SB 9 aims to address the housing shortage by simplifying the process to create more units on single-family zoned lots, which could suggest a more flexible approach towards constructing ADUs first.
  • While the bill primarily focuses on lot splits and the development of up to four residential units, it doesn’t explicitly prohibit building an ADU before a main residence, leaving some room for interpretation at the local level.
  • The practicality of building an ADU first hinges on how local governments adapt their zoning regulations in response to the new state law.
  • Property owners interested in this route should actively engage with local planning departments as they may have specific requirements or interpretations of state laws affecting the order of construction.

Understanding SB 9’s nuances is crucial for homeowners who are considering an unconventional approach to developing their properties with an ADU as the initial focal point.

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Case Studies: Examples of ADU Construction Before Main Houses

Real-life applications often speak louder than theory, and in the case of ADUs, they illuminate possibilities under the California sun. Los Angeles provides a fascinating example, where a homeowner elected to construct a detached ADU on a vacant lot. Embracing the relaxed rules of the city’s ADU ordinance, this standalone unit became the first structure on the property; the main house followed months later. This sequence appealed due to scheduling flexibility and cost management—it allowed the property owner to offset expenses by renting out the ADU sooner.

In the heart of Silicon Valley, a similar story unfolded for a couple keen on downsizing. They opted to build a compact ADU before erecting their future retirement home. By living in the ADU themselves, they could supervise the construction of their main residence, ensuring every detail was to their taste, without the need for temporary housing elsewhere.

These instances are a testament to the adaptability of ADU regulations in California, showcasing that they can be tailored to the varied needs of homeowners. From creative approaches to space utilization to strategic financial planning, building an ADU before the main residence opens up a world of opportunities that can align with personal circumstances and long-term housing goals.

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