What Is an ADU? A Smart Move for Modern Living

Long popular on the West Coast, accessory dwelling units have quickly spread in popularity as an intelligent solution to a variety of housing needs. But what is an ADU exactly, and what makes these extra spaces so compelling? 

An ADU (also known as an ancillary suite, casita, pool house, granny flat, backyard cottage, or in-law suite, among many other names) is simply a secondary residential unit located on the same lot as a single-family home. 

But ADUs are also an attractive space solution: they provide a dedicated, private space for guests; act as a standalone home office or art studio away from the distractions of your main home; increase your property value; and make efficient use of underutilized yard space, garages or attics—all while creating opportunities for rental income, aging in place, and sustainable community development.

What Makes an ADU the Ultimate Flexible Living Space?

Flexibility is the true hallmark of the ADU. While often associated with the tiny house movement, today’s ADUs are anything but one-size-fits-all; and with modern furniture solutions, you can outfit even the smallest ADU with all the comforts and conveniences you’d expect from a large single-family home. 

Reimagining these units as multifunctional home offices, guest rooms, extra living spaces, creative workspaces, or even private home gyms can reignite the love for your home.

With a diverse range of transforming and space-saving furniture options, Resource Furniture is uniquely suited to meet the demands of ADUs. We’ve brought this vision to life in numerous high-profile ADU projects—including several with HGTV’s The Property Brothers on hit shows like Celebrity I.O.U. and Brother vs. Brother. These projects reimagined accessory units into everything from stylish guest suites to luxury short-term rentals that rival boutique hotel stays. 

Types of ADUs: Detached, Attached, and Everything Between

ADUs come in several configurations, defined by how they’re built in relation to the main residence.

Here are some of the most common forms of ADU’s we’ve seen from Resource Furniture clients:

• Detached ADUs are stand-alone structures set apart from the main house, often called backyard cottages. Detached ADUs tend to offer the most privacy and autonomy, making them ideal rental units or as a private oasis.

• Attached ADUs share a wall with the main residence, often built as additions with a separate entrance or by converting an existing space. Attached ADUs may sometimes be limited by setback requirements and other zoning regulations, but they can often be more cost-effective to build.

• Conversions are a type of attached ADUs, with the most common examples being garage conversions and basement units (also known as internal ADUs). Conversions are an excellent way to maximize livable space within your home’s existing footprint (though these often require creative design solutions due to size or code constraints).
  
  Still, that hasn’t stopped garage and basement ADUs from becoming the most common type of accessory structure in the U.S. With today’s innovative design and furniture solutions, creating a comfortable, functional ADU—even in unconventional spaces—has never been easier.
  
  (Bonus: We’ve compiled our best design tips and furniture recommendations for converted areas like basements, attics and garages, addressing the common challenges these spaces often present such as lower ceiling heights and limited natural light.)

While every ADU comes with its own design, logistical, and permitting considerations, understanding the different types can help you determine the best ADU option for your property, budget, and lifestyle goals.

Why ADUs Are on the Rise (And Why They Make Sense)

Several factors are fueling the ADU boom, from rising housing costs and limited housing inventory to demographic shifts, but perhaps the main driver behind the surge in ADU construction has been legislative reform. 

California has led the charge in the arena.  Since 2017, changes to zoning restrictions, parking minimums, setback requirements and minimum lot size have had a profound impact: ADU permits in the state skyrocketed from just over 1,100 in 2016 to nearly 25,000 in 2022. Over a six-year span, more than 84,000 ADUs were permitted, and approximately 45,000 of those have already been completed—a completion rate that rose from 35% in 2018 to 72% in 2022.

California’s regulations now serve as a blueprint for other states, with Washington, Oregon, Maine, Colorado, and many others following suit with their own relaxed ADU laws. 

ADUs simply make sense. They provide practical solutions to a broad range of needs by providing opportunities for passive rental income, raising property values, offering overflow guest space, and providing dedicated home office space for the growing population of remote workers—all without the need to uproot.

What You Need to Know Before Building

Before breaking ground on an ADU, you should familiarize yourself with local zoning laws, ordinances, and permitting requirements. These rules can affect everything from unit size and placement to parking and owner occupancy, and they can often vary by municipality. 

Be sure to thoroughly research the local regulations where you live and address any questions with your city’s building department before embarking on your ADU project. 

Once you have established your ideal floor plan, Resource Furniture's space and design consultants can help you navigate your layout choices, recommending multifunctional furnishings and modular storage solutions that make the most of your ADU’s available square footage. 

Designing Your ADU: Small Spaces, Big Style

Thoughtful design is essential in maximizing an ADU’s comfort and functionality. Smart layouts, ample natural light, and premium finishes can make even a 400-square-foot unit feel expansive and refined.

Multifunctional furniture—like transforming tables, wall beds, and modular shelving—can turn a small studio into a dynamic space that evolves throughout the day. Resource Furniture’s collections are frequently featured in ADUs, ensuring that every square foot serves a purpose.

High-end materials, custom cabinetry, and seamless indoor-outdoor transitions can further elevate the experience. A well-designed ADU should feel like a natural extension of the main home.

How Much Does an ADU Cost?

The cost to build an ADU can range anywhere from $100,000 to $400,000 or more, depending on factors like size, location, construction method, and interior finishes and furnishings. Detached units tend to be more expensive than conversions due to the need for separate foundations and utility hookups.

Key cost drivers include:

• Site preparation and permitting

• Utility connections (water, sewer, electricity)

• Design and architectural fees

• Materials and labor
  
  

Smart, Stylish Uses for Your ADU

The true beauty of an ADU lies in its adaptability. A few standout use cases:

Guest House

Create a luxurious retreat for visiting friends and family, complete with a kitchenette, spa-like bath, and stylish transforming furnishings. Consider outfitting your guest house ADU with a multifunctional wall bed with an integrated sofa—like the Swing Chaise or Oslo Sectional—allowing guests to effortlessly convert the unit’s sleeping space into their own private living area during the day.

These particular models have the added benefit of hidden under-seat storage compartments, ideal for storing extra bedding in a small guest house. Pair with a height-adjusting coffee-to-dining table for added versatility.

For a particularly well-executed example, look no further than the premiere episode of Celebrity I.O.U. where Brad Pitt transformed a detached garage into a luxe guest suite for his longtime friend and makeup artist using these very pieces. The result: a compact, elegant retreat outfitted with a Swing Chaise wall bed, Passo table, and modular storage that made every inch count.

Garage Conversion

Even the most unassuming spaces—like unfinished garages—can be transformed into sophisticated, multifunctional ADUs.

In another memorable Celebrity I.O.U. episode, Wilmer Valderrama surprised his best friend by converting a garage into a guest suite for their extended Samoan family. The space featured two Circe wall beds and surrounding modular cabinetry, demonstrating how transforming furniture solutions can create beautiful, functional ADUs spaces for large households.

Home Office

Design a distraction-free workspace tailored to meet the demands of today’s remote work, incorporating built-in storage and multifunctional desks to maximize efficiency without sacrificing style. Long gone are the days of fretting over a messy virtual meeting background; an ADU office is a private home workspace away from home. 

This was exactly the vision behind Santa Monica residents Michael Soloman and Naomi Lieberman’s detached garage conversion. Working with Minarc architects and Resource Furniture, they designed a serene backyard WFH retreat complete with a Swing Chaise transforming wall bed. The project was featured in The LA Times for its unique application of prefab design and multifunctional furnishings.

Wellness Space

Think yoga studio, meditation room, or even a compact home gym. An ADU can double as your own, personal wellness oasis just steps away from your main house, outfitted with serene finishes, concealed storage for mats and equipment, and a fold-down desk that doubles as an altar or reading nook. 

Long-Term Rental

Generate passive income with a turnkey rental unit designed for long-term tenants. Transforming and multipurpose furnishings like wall beds, transforming tables, flexible seating and modular storage can create an elegant, functional living space with all the comforts of a much larger unit, raising the appeal to renters. 

Airbnb or Short-Term Rental

Stand out in a competitive short-term rental market by transforming your ADU into a design-forward, multifunctional guest suite.

Resource Furniture's elegant, space-saving pieces allow the space to shift effortlessly between sleeping, lounging, dining, and working. Durable, high-performance materials and finishes ensure your rental stays stylish and low-maintenance, while hidden storage keeps clutter at bay for a polished guest experience.

Multigenerational Living

Provide a private, dignified space for elderly parents or adult children living at home. Easy-to-operate wall beds—such as the Tonale Sectional wall bed featuring a button-operated, motorized open/close—offer comfort and accessibility, while integrated shelving, storage and lighting options keep the footprint minimal and the environment safe.

The result is an elegant, supportive space that nurtures independence while remaining just steps away from the main household.

Next Steps: Resources and What to Explore Next

If you're inspired to explore what an ADU could look like on your property, start by reviewing your city's zoning and permitting guidelines. Many municipalities offer online ADU resources, including pre-approved plans and cost calculators.

For personalized guidance on design, style, and storage for your ADU, speak with one of our designers or visit a showroom. At Resource Furniture, our experts can help you visualize how smart, space-saving design can transform even the smallest ADU into a luxurious retreat.