An accessory dwelling unit (ADU) is a secondary home located on the same property as a primary residence. It provides independent living space and can be designed to accommodate family members, guests, or long-term rental tenants, subject to applicable requirements.
ADUs have become an increasingly popular option for homeowners who want to make better use of their property without moving to a different home. Depending on the property's layout, an ADU may be built as a separate backyard structure, attached to the existing home, or created by converting an existing space.
If you're considering building an ADU, understanding the different types, potential benefits, and planning requirements is a useful first step.
ADU stands for Accessory Dwelling Unit. It is a separate residential living unit associated with an existing or proposed primary home.
An ADU generally includes the essential facilities needed for independent living, such as a kitchen, bathroom, sleeping area, and living space. The exact requirements depend on the applicable building codes and regulations.
You may also hear ADUs referred to as granny flats, in-law units, backyard cottages, or secondary homes. Although these names are often used interchangeably, the legal classification of a particular structure depends on the applicable requirements.
The best ADU type for your property depends on the available space, your intended use, your budget, and local requirements.
A detached ADU is a separate structure located apart from the primary residence, often in a backyard.
This option can provide greater separation and privacy between the main home and the additional living space. The layout, size, access, and placement will depend on the property and applicable development standards.
Detached ADUs are often considered by homeowners who want to create a separate residence for relatives, guests, or potential tenants.
An attached ADU is connected to the primary residence but designed to function as an independent living unit.
Depending on the home's configuration, this approach may make use of an addition or an existing portion of the structure. Planning should account for access, privacy, utilities, building requirements, and how the new space connects to the existing home.
A garage conversion transforms an existing garage into residential living space that meets applicable ADU requirements.
Because a structure already exists, converting a garage may be an attractive alternative to building an entirely separate unit. However, an existing garage is not automatically suitable for conversion. Structural conditions, ceiling height, insulation, foundations, utilities, and other requirements may affect the scope of work.
Learn more about our garage conversion services.
A Junior Accessory Dwelling Unit, commonly called a JADU, is a smaller type of unit created entirely within a proposed or existing single-family residence. California law generally limits JADUs to 500 square feet and includes additional requirements.
JADUs have different rules from standard ADUs, so homeowners should verify which option is appropriate for their property and intended use.
An ADU can serve several purposes depending on the homeowner's needs.
An ADU can provide a separate living area for adult children, aging parents, extended family, or guests. It can offer more independence while keeping family members close by.
Some homeowners explore ADUs as a way to create a rental property. Actual rental income depends on factors such as location, market conditions, construction costs, occupancy, and applicable rental regulations. Income is not guaranteed.
An ADU can make an existing property more adaptable to changing household needs. A unit initially used for family members may serve a different purpose later, provided the intended use is permitted.
An ADU may add functionality and appeal to a property. However, the effect on resale value depends on local market conditions, the quality and legality of the construction, and other property-specific factors.
Building an ADU involves several stages. The details vary by property and jurisdiction, but the following sequence is a useful starting point.
Start by deciding how you plan to use the ADU. Consider who will occupy it, the type of living space required, the level of privacy desired, and the features that matter most.
Review the available space, access, existing structures, utility connections, and other site conditions. A professional assessment can help identify constraints before substantial time or money is committed.
Choose a suitable layout and determine the project's expected scope. Depending on your needs, you might consider a custom layout or a more standardized design approach.
Before construction, verify the applicable zoning, building, utility, and permitting requirements with the relevant local authority. Approval requirements and timelines can vary.
Once the necessary approvals and preparations are in place, construction can proceed according to the agreed scope, schedule, and project requirements.
For help understanding the construction process, explore our ADU construction services.
There is no single price that applies to every ADU project. Costs depend on the type and size of the unit, site preparation, foundation requirements, utilities, finishes, design, permitting, and construction complexity.
A garage conversion may have a different cost profile from a new detached ADU, but an existing structure can still require substantial upgrades. Comparing options should involve the full project scope rather than just the initial construction estimate.
Before moving forward, homeowners should establish a realistic budget, understand what is included in the proposed scope, and account for potential additional expenses.
ADU projects generally require applicable permits and approvals. The requirements depend on the project type, property, and jurisdiction.
In California, state law provides a framework for ADU development, while local agencies administer relevant applications and requirements. Homeowners should consult the current rules for their property rather than relying on assumptions or outdated online information.
An ADU may be worth exploring if you need additional living space, want to accommodate family members, or are considering a potential rental unit.
The best starting point is to identify your goals, evaluate your property's conditions, and understand the likely design, permitting, and construction requirements before deciding how to proceed.
Every property is different, and the right approach begins with understanding your specific needs.
ADU Specialist Group can help you explore the next steps for your project, from understanding construction options to discussing planning, permitting support, and project coordination.
Ready to explore your options? Contact our team to discuss your ADU project.