ADU Design: 5 Must-Have Features

7min read
by Olesia Chikunova, ADU Specialist.

ADUs may be small, but their design requires detailed planning. In this article, we dive into the must-have features for your ADU design! 

Discuss them with your ADU designer before finalizing construction documents. Some details need to be taken care of by your general contractor before the foundation is poured.

Are you looking to use that backyard space well — and stumbled upon ADUs? An Accessory Dwelling Unit is one of the best ways to extend your living space while massively adding to the value of your property. Previously, ADUs were known under different names: granny flats, in-law units, backyard cottages. You may have even heard the phrase “carriage house”. Some jurisdictions allowed for a guest house but made it quite tricky to get a building permit. 


When the housing shortage became hard for politicians to ignore, new legislation introduced several types of ADUs in California. Every single-family home can add a detached ADU or attached ADU plus convert existing space into a junior accessory dwelling unit. Even some multifamily buildings can turn unused available space into an ADU.

ADU design with open floor area

The housing crisis was not the only reason ADUs became so popular. The second reason is demographics. More and more people realize they would like to stay in their Bay Area homes as they grow older but face high living costs. An ADU project allows one to plan for a happy retirement in smaller secondary units while renting out a primary home for additional income.


As an additional benefit, newly built backyard homes are often built better than the main house. You can make a conscious design decision for a high-performance ADU and invest in energy and water efficiency to keep monthly costs down.


Now imagine having two rentals for extra income. The best way to keep construction costs down is to convert existing space. For example, you can convert a garage into a standard accessory dwelling unit (a detached garage or an attached one) and a primary bedroom into a junior accessory dwelling unit. That may be your best bet to stay in your favorite neighborhood for as long as you want to.


But before hopping onto the bandwagon, learning about the do’s and don’ts of ADU design pays off. 


Designing with the mindset of investment is essential. But what exactly does this mean? Watching the costs and designing for small spaces.

Check the primary residence’s property value and ensure you do not overpay. You want to gain some additional equity once the project is completed.

How do you approach ADU design as an investment?

In short, your design should accommodate as many people as possible. Young and old. Kids and older adults. 

Things like pulls (not knobs) can make a home more comfortable for older folks.

A home without curbs and wider doorways helps those who cannot move freely.

Someone with a broken leg might need extra help for a short time, and a universally designed home steps up to the challenge. There will be no need for urgent last-minute house modifications. You always need that grab bar the day after you didn’t.

Have you ever tried carrying a baby while opening a door? Universal design makes it easier for parents to juggle their superhero duties.

For those taking care of someone with a disability, a universally designed home makes daily tasks smoother.

Universal design makes homes welcoming for everyone.

Visual and Vibrating Alerts:

    • Install visual or vibrating alerts in addition to audible ones. For example, instead of relying solely on a doorbell’s sound, you can add a visual indicator like a flashing light or a device that vibrates to alert someone when the doorbell rings. This ensures that the person with a hearing disability doesn’t miss important signals.

Open Design and Clear Sightlines:

    • If someone uses sign language or lip reading, having unobstructed views between family members in common living areas can make communication more seamless.

Smart Home Devices:

    • Invest in smart home devices with visual or tactile feedback. Modern home devices, like thermostats, smoke detectors, or security systems, can be integrated with smart technology. Choose appliances that provide visual cues or can be connected to a vibrating alert system to keep the person informed.

Assistive Listening Devices:

    • Provide assistive listening devices. These devices, like personal amplifiers or loop systems, can enhance the clarity of sounds in specific areas of the home. For example, a TV listening system that transmits audio directly to a headset can make watching TV more enjoyable for someone with a hearing disability without disturbing others.

Well-Lit Spaces:

    • Ensure well-lit spaces for effective communication. Good lighting is essential for lip reading and sign language. Consider installing bright and adjustable lighting fixtures in key areas, such as the living room or dining area. 


The Secret Superhero of ADU Design

Universal design is like the superhero of making things awesome for everyone, no matter who they are. It’s all about creating spaces that work for as many people as possible, whether big or small, young or old or have different abilities.

  1. Be Clear and Simple: Imagine you’re playing a game, and the rules are so easy to understand that everyone can join. That’s what universal design is about—making things simple. Like traffic lights! Red means stop, and green means go. 
  2. Use Big Buttons and Text: Think about a computer game for toddlers with huge buttons, and the words are easy to read. That’s like universal design—it helps everyone, especially those who might have trouble seeing small stuff.
  3. Add Pictures and Symbols: Have you ever been to a place where there are pictures to show you what’s what? Think of a bathroom sign with a picture of a person. Universal design uses images and symbols to help everyone understand, regardless of language.
  4. Make it Comfortable: Picture the comfiest chair you’ve ever sat in. Universal design is like that—it makes things comfortable for everyone. Maybe it’s a ramp instead of stairs so everyone, including someone in a wheelchair, can get in easily.
  5. Include Everyone in the Fun: Imagine a playground where everyone can play, no matter if they can run super fast or need a bit of help. Universal design wants everyone to join the fun, just like a playground with something for everyone.
  6. Think About How People Move: Universal design is like a dance floor where everyone can bust a move. It thinks about how people move and ensures everyone can get around, whether walking, rolling, or skipping.
  7. Plan for Surprises: Sometimes, things don’t go as planned. Universal design is like having a backup plan for surprises, like having an elevator when the stairs are too tricky for someone or a one-handle faucet when you have a broken wrist.

Remember, it’s like making the most incredible game or playground where everyone is invited and can have a blast! 

And for a sprinkle of magic, here is a secret: the best universal design is invisible.

curbless shower

How to minimize vacancy if your ADU is a rental

Let us get serious. If you ever decide to turn your ADU into a rental unit, it will make sense to make it comfortable for a broader range of applicants. Here is why it makes sense to design for different abilities:


According to the Centers for Disease Control and Prevention (CDC), in 2019-2020, the prevalence of obesity among adults in the United States was approximately 42.4%. This means that nearly 4 in 10 adults have obesity.


According to the National Institute on Deafness and Other Communication Disorders (NIDCD), approximately 15% of American adults (37.5 million) aged 18 and over report some trouble hearing.


According to the National Health Interview Survey (NHIS) in 2019, about 12 million Americans aged 40 years and older were visually impaired. This includes conditions like blindness or difficulty seeing even with glasses.


By adding good design to your new ADU, you are ensuring additional income with zero vacancies. You wouldn’t believe how fast well-designed ADUs get off the market and become long-term rentals.


Universal design is like a magical spell that makes homes awesome for everyone living there or visiting—regardless of age, abilities, or circumstances!

If you want to create an ADU that gives you a bang for your buck, keep reading! In this article, we discuss the must-have features for your ADU design. Paying attention to these will make sure your space is big on flexibility, simplicity, and safety! And keeps giving you back for years.

open space family room

Open Floor Plans

ADU Design Feature #1

Since ADUs are small, roominess is a top factor to consider when designing your ADU. And when creating an illusion of more space, an open floor plan takes the prize. Without walls dividing the room, open floor plans turn ADUs into open and spacious interior spaces. Its compact footprint makes a large kitchen double up as a dining area. Full bathrooms can serve as laundry rooms. 

It is also important to note that universal design focuses on creating open, flexible, and adaptable spaces. And that’s precisely what an open-floor plan can help you achieve. It is open and airy, but beyond that, it provides flexibility in design. For example, it is adaptable in furniture placement, so you can move your furniture around when needed.

Such floor plans also have plenty of other benefits for your ADU design. For example, they allow enhanced air circulation (because there are no walls to obstruct airflow). The less complex structural engineering also means the design is simple. 

dining and kitchen area in open space floor plan

Optimal Spatial Planning

ADU Design Feature #2

Spatial planning is one of the most critical features in ADU design — but why? Optimal space planning ensures smooth traffic flow in your ADU so people can move around the space without bumping into things. The following are some tips to ensure your ADU has appropriate spatial planning.

  1. Closely observe the natural traffic patterns in your ADU design. That is the pathway along which people tend to move around the most.
  2. Work on clearing these pathways. Remove any obstacles in the way; also, make sure the way you place furniture items allows enough room for movement.
  3. Consider multifunctional furniture pieces — these ensure you have enough room to store essentials in your ADU while freeing up valuable space.
  4. Maximize the use of vertical space (some ideas would be installing shelves and wall-mounted cabinetry). This helps free up floor space for easy movement.
  5. Further, save space by using pocket doors. These slide into the wall (when you open them) instead of swinging around over the floor.

Also— be sure to pay attention to circulation space. So, when you place furniture and decor items, consider the space needed for opening drawers, some appliances, doors, etc. This makes sure safety is a priority and any possible accidents are avoided.

Flexible Design

ADU Design Feature #3

Flexibility truly means accommodating different needs — such as those of differently-abled people — and changes in circumstances. Such flexibility should be a priority in your ADU design. Aim to design for inclusion (and comfort) by choosing kitchen and bathroom features accessible by all types of people. Remember, good design enables, and bad design disables.

Some ideas to consider for your ADU are:

  1. Easy grip cabinet pulls are designed with large handles/bars that are easier to grip (compared to traditional pulls or knobs). Similar are lever-handled doors, which are easier to operate by people with limited hand mobility.
  2. Multi-height countertops can suit different users. For example, lower countertop sections are ideal for seated tasks (that someone in a wheelchair may prefer). Often, people from the same household are of different heights, so they will also need different countertop heights to feel comfortable when preparing food.
  3. Adjustable shelving helps users customize the storage space according to changing circumstances. For example, the shoe section may be smaller for summer sandals and bigger for winter boots.
  4. Curbless entries between rooms refer to leveled transitions between rooms (without differences in height). For example, a walk-in shower can ensure someone in a wheelchair can enter easily. Curbless showers are also designed with sloping floors so water can quickly drain away.
  5. Non-slip floors reduce the risk of slipping, so everyone is safe and can quickly move around the ADU.
  6. Installing grab bars near the toilet and in the shower can support people with mobility or dizziness issues.
  7. Invest in appliances that comply with the ADA (Americans with Disabilities Act) guidelines. For example, ADA-compliant ovens have side-hinged doors (these are easy to access by those in a wheelchair). For similar reasons, refrigerators have adjustable shelving. Tip: Ensure the appliances have easy-to-understand controls so everyone can use them easily.
  8. Roll-in options for sinks and cooktops create space beneath a sink or cooktop, allowing wheelchair users to roll underneath.

Ventilation Considerations

ADU Design Feature #4

ADUs are small in size, so they can feel congested. The solution? A vaulted ceiling, more windows, and proper ventilation. The latter controls the moisture levels and temperature within the ADU, all while ensuring a good quality of indoor air.

  1. Install exhaust fans in high-moisture areas (most likely the kitchen and bathroom).
  2. Consider wide doorways; these promote ventilation and are feasible for people with moving support (such as walkers).
  3. Choose large windows for your ADU design — and place them strategically so cross-ventilation can occur.

As a bonus, you can install air quality sensors that monitor the ADU air quality and adjust ventilation accordingly. Look into ERVs for an additional level of comfort.

multiple types of windows in living room

Adequate Lighting

ADU Design Feature #5

Lighting should be on the top of the list when jotting down must-have features for your ADU. This is because enough lighting ensures your ADU is safe to use during nighttime (as it helps prevent falls and accidents). It also helps set the mood of the ADU — and goes beyond to reduce the eye strain levels of the residents.

Of course, lighting is vital for everyday tasks as well. ADU lighting design typically focuses on the following fixtures—

  1. Skylights to capture natural light (installed on the roof)
  2. General lighting (this can be a central chandelier)
  3. Task lights to illuminate areas for your various everyday tasks (for example, under cabinet lighting and hood lights in the kitchen)

Regarding daylighting, northern light is preferred. This means it creates an even, diffused light, lending to a soft ambiance in the ADU interior. Placing larger windows on the northern side of the ADU can help achieve the purpose.

Additional tips to keep in mind while lighting your ADU are:

  1. Reduce glare in your ADU interior. For controlling daylight levels, use window treatments. For artificial light sources, a dimmer will do the trick.
  2. Position your switches and outlets, considering the age (and accessibility) of various age groups. For example, keep them at a low height and in easy-to-reach locations (e.g., near entrances, beside the bed, etc.). 


ADU Design: Final Words

While there are many considerations for ADU design, it’s always easier to start with the must-have features. Also— remember that ADUs should be designed with maintenance in mind (easy-to-clean materials are key!).

open space kitchen and living area

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