Building an ADU Unit for Your Home in Los Angeles: A Comprehensive Guide

Accessory Dwelling Units (ADUs) have become increasingly popular in Los Angeles as homeowners seek to maximize their property’s potential. These secondary units, also known as granny flats, in-law units, or backyard cottages, offer a versatile solution for additional living space, rental income, or housing for family members. This comprehensive guide will walk you through the process of building an ADU in Los Angeles, covering everything from initial planning to construction and occupancy.

What is an ADU?

An ADU is a secondary dwelling unit on the same lot as a primary residence. It can be attached to the main house, detached, or converted from existing space within the home, such as a garage. ADUs are self-contained, with their own kitchen, bathroom, and living area, providing complete, independent living quarters.

Benefits of Building an ADU

  1. Increased Property Value: ADUs can significantly boost the value of your property by adding additional living space.
  2. Rental Income: Renting out an ADU can provide a steady stream of income, helping to offset mortgage payments or other expenses.
  3. Flexible Living Arrangements: ADUs offer flexible living options for extended family, elderly parents, or grown children, providing privacy while keeping loved ones close.
  4. Housing Solutions: In a city with high housing demand like Los Angeles, ADUs contribute to the availability of affordable housing options.

Step 1: Understand Local Regulations

Before embarking on an ADU project, it’s crucial to understand the local regulations and requirements in Los Angeles. The city has specific guidelines for ADUs, influenced by state laws aimed at increasing housing density. Key regulations include:

  • Lot Size and Zoning: ADUs are allowed in most residential zones. There is no minimum lot size requirement, but the lot must have a single-family or multi-family dwelling.
  • Unit Size: Detached ADUs can be up to 1,200 square feet, while attached ADUs are limited to 50% of the existing home’s size, with a maximum of 1,200 square feet.
  • Setbacks: ADUs must adhere to setback requirements, typically 4 feet from the side and rear property lines.
  • Height: The maximum height for detached ADUs is generally 16 feet, but can be higher in some cases if certain conditions are met.
  • Parking: One parking space is required for ADUs, but this requirement is waived if the property is located within half a mile of public transit, among other exceptions.
  • Permitting: Building permits and other approvals from the Los Angeles Department of Building and Safety (LADBS) are required before construction begins.

Step 2: Plan Your ADU

Once you understand the regulations, the next step is to plan your ADU. This involves deciding on the type of ADU, its design, and its location on your property.

Types of ADUs

  1. Detached ADU: A separate structure built on the property, offering complete independence from the main house.
  2. Attached ADU: An extension to the existing home, sharing a wall but with its own entrance.
  3. Garage Conversion: Transforming an existing garage into a living space, a cost-effective option since the structure is already in place.
  4. Interior Conversion: Converting part of the existing home, such as a basement or attic, into an ADU.

Design Considerations

  • Functionality: Ensure the layout maximizes space and functionality, including a kitchen, bathroom, living area, and storage.
  • Privacy: Design the ADU to provide privacy for both the occupants of the main house and the ADU.
  • Aesthetics: The ADU should complement the architectural style of the main house and blend seamlessly with the surrounding environment.
  • Accessibility: Consider incorporating universal design principles to make the ADU accessible for all, including those with mobility challenges.

Step 3: Hire Professionals

Building an ADU is a complex process that requires the expertise of various professionals. Key players include:

  • Architect: An architect will help design the ADU, ensuring it meets all regulatory requirements and your personal preferences.
  • Builder/General Contractor: A reputable builder will manage the construction process, coordinating with subcontractors and ensuring the project stays on schedule and within budget.
  • Engineer: Structural, civil, and mechanical engineers may be needed to address specific aspects of the project, such as foundation work and utility connections.
  • Permit Expeditor: In a city like Los Angeles, navigating the permitting process can be challenging. A permit expeditor can help streamline the process, ensuring all necessary permits are obtained efficiently.

Step 4: Secure Financing

Financing an ADU can be achieved through various methods, including savings, home equity loans, construction loans, or financing programs specifically for ADUs. Research and choose the option that best suits your financial situation. Key considerations include interest rates, repayment terms, and the overall impact on your finances.

Step 5: Obtain Permits

Before construction begins, you must obtain the necessary permits from LADBS. The permitting process involves submitting detailed plans and documentation, including:

  • Site Plan: A detailed drawing showing the property, existing structures, and the proposed ADU.
  • Floor Plans: Layout of the ADU, including dimensions and the placement of rooms, doors, and windows.
  • Structural Plans: Details of the construction, including foundation, framing, and roofing.
  • Electrical and Plumbing Plans: Layout of electrical systems, plumbing fixtures, and connections to existing utilities.

The permitting process can take several weeks to several months, depending on the complexity of the project and the workload of the permitting office. Be prepared for possible revisions and additional documentation requests.

Step 6: Begin Construction

With permits in hand, construction can begin. The construction process for an ADU typically involves several phases:

  • Site Preparation: Clear the area where the ADU will be built, including any necessary grading or demolition of existing structures.
  • Foundation: Lay the foundation according to the approved plans. This could involve pouring concrete slabs, constructing footings, or other foundational work.
  • Framing: Erect the frame of the ADU, including walls, floors, and roof structures.
  • Utility Connections: Install plumbing, electrical, and HVAC systems, ensuring they are correctly connected to existing utilities.
  • Exterior Work: Complete the exterior, including siding, roofing, windows, and doors.
  • Interior Work: Finish the interior, including insulation, drywall, flooring, cabinetry, and fixtures.
  • Landscaping: Restore any disturbed landscaping and create outdoor spaces that complement the ADU.

Regular inspections will be required throughout the construction process to ensure compliance with building codes and regulations.

Step 7: Inspections and Final Approval

As construction progresses, various inspections will be conducted by the city to ensure the ADU is built according to code and the approved plans. Key inspections include:

  • Foundation Inspection: Verifies that the foundation is constructed correctly.
  • Framing Inspection: Ensures the framing is done according to plan.
  • Plumbing and Electrical Inspections: Check that these systems are installed safely and meet code requirements.
  • Final Inspection: A comprehensive review once construction is complete to ensure everything complies with regulations.

Passing all inspections is crucial to obtaining a Certificate of Occupancy, which allows the ADU to be legally occupied.

Step 8: Furnish and Decorate

With construction complete and final approval obtained, it’s time to furnish and decorate the ADU. Consider the following tips:

  • Furniture: Choose furniture that fits the space and meets the needs of the intended occupants. Multifunctional and space-saving furniture can be especially useful in smaller ADUs.
  • Decor: Decorate the ADU to create a comfortable and inviting atmosphere. Use colors, textures, and accessories that complement the overall design.
  • Appliances: Equip the ADU with necessary appliances, such as a refrigerator, stove, and washer/dryer. Energy-efficient appliances can help reduce utility costs.
  • Technology: Consider incorporating smart home technology, such as programmable thermostats, smart locks, and security systems, to enhance convenience and security.

Step 9: Move In or Rent Out

Once the ADU is furnished and decorated, it’s ready for occupancy. If the ADU is intended for family use, help your loved ones settle in and make the space their own. If you plan to rent it out, take the following steps:

  • Marketing: Advertise the ADU through various channels, such as online rental platforms, social media, and local listings.
  • Screening Tenants: Conduct thorough tenant screenings, including background checks, credit checks, and references, to ensure reliable and responsible renters.
  • Lease Agreement: Draft a clear and comprehensive lease agreement that outlines the terms of the rental, including rent amount, payment schedule, maintenance responsibilities, and rules for the property.


Building an ADU in Los Angeles is a rewarding investment that offers numerous benefits, from increased property value to additional living space and rental income. By understanding local regulations, carefully planning your ADU, and working with experienced professionals, you can successfully navigate the process and create a valuable addition to your property. Whether for family use or as a rental unit, an ADU can enhance your lifestyle and provide long-term financial benefits.