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Accessory Dwelling Units or ADUs are the cool new answer to today’s housing affordability woes.

Think of them as mini-homes on your property – they’re perfect for everything from a private space for your in-laws to a neat rental spot.

The problem is there are just so many designs! And how can one small space really fit everything I need it in?

I have found the best ADU floor plans under 500 sq ft for your needs.

This article will showcase studio ADU plans, one-bedroom ADU plans, and ADU plans with office space. 🏠

I also offer design tips and share why each floor plan is a great choice. I even took a great ADU plan and added some design ideas and plan variations to create a space with an office space, sleeping for 6, and a living room that can be closed for added privacy.

We’re diving into ADU plans about making the most out of every inch. 📏

So, let’s get creative and see how these little wonders can make a big impact.

Disclosure: This post may contain affiliate links, meaning I can earn commissions. If you decide to purchase through my links, it is at no cost to you.

THE Best Studio ADU Plans Under 500 Square Feet

What are Studio ADUs? A studio ADU maximizes living space by combining the living, sleeping, and dining areas into one open-concept room.

Many will opt for this ADU design if their ADU space will function as a guest suite or in-law suite when needed and flex or additional space during other times.

This size is more affordable to build.

Mila floor plan
PinUpHouses.com

About this ADU Floor Plan:

This plan combines living and sleeping into a large space but is still divided by the built-in storage for some separation.

The kitchen and bathroom are located near each other for efficient plumbing design.

Two sets of double windows allow lots of natural light into the space. The front porch gives you some connection to the outdoors.

Square Footage: 345 square feet

Dimensions: 18’2″ x 19′

PinUpHouses.com

Who should consider this plan:

  • If your space is for family members when needed and will serve another function the rest of the time, this plan is ideal.
  • The undefined bedroom space allows you to transform the space daily into other uses, such as a work or flex space.
  • If you are looking for a budget-friendly option with minimal walls and plumbing utilities near each other.

Design ideas:

  • Install a Murphy Bed in the sleeping space for more functionality
  • Opt for a loft bed in the sleeping space to utilize the space below for an office area
  • Add a room divider between the sleeping and living space for extra privacy
  • Install a sliding door to the bathroom to save space
DID YOU KNOW

An ADU with 400 square feet or less is considered a tiny house.

Chloe floor plan
PinUpHouses.com

About this ADU Plan:

The Chloe Cabin plan prioritizes a good front porch. The home’s interior offers efficient living with a large space for the eating and living space.

The sleeping space is in a loft area, offering a little separation and privacy.

The front of the home has most of the windows offering lots of natural light.

Square Footage: 278 square feet

Dimensions: 17′ x 16’5″

PinUpHouses.com

Who should consider this plan:

  • Since this space is smaller, the cost to build will be reduced.
  • If you need more hangout space separate from the main house, this plan is ideal since it does not prioritize the sleeping space.

Design ideas:

  • Instead of a bench with storage, opt for one that converts into additional sleeping space if you will be having guests
  • Adding skylights to the backside of the roof would offer additional light to the loft
  • Consider putting a sofa where the current dining space is and adding a fold-down table where the library is for your dining space
  • Building your stairs with built-in storage
Truoba-Mini-121-ADU-floor-plan

About this ADU Plan:

Efficient living meets Function in this small adu design. This versatile plan is a perfect guest house for your backyard cottage project needs.

This space is small but has large windows and a sizable sun deck. The exterior shell is the perfect space to turn this into a modern ADU.

The design could allow more privacy from the primary house since most windows are only on two sides.

Square Footage: 285 square feet

Dimensions: 14’4″ x 20’9″

Truoba.com

Who should consider this plan:

  • You have beautiful natural surroundings and want to showcase that through large windows.
  • If you only have a small space to work within your backyard.
  • If you have an adult child living at home and want a separate space for their privacy.
  • Your adu project will be a She Shed or Man Cave Space.

Design ideas:

  • A Multi-functional Murphy Bed would be ideal in this space.
  • The space next to the bathroom could be a workspace, pantry space, or extra storage.
  • Consider swapping the window in the sleeping space for a door to add on the space easily.
  • Position the structure so the roof faces south for future solar panels
AD 399 sf adu floor plan
ArchitecturalDesigns.com

About this ADU Plan:

This ADU plan uses an efficient layout by locating the kitchen and bathroom nearby.

The small porch allows a quaint place to enjoy some of the outdoors. This plan utilizes a large room concept for all living space functions.

Square Footage: 399 square foot

Dimensions: 20′ x 22′

Architecturaldesigns.com

Who should consider this plan:

  • You are looking for an ADU that is also a Tiny House
  • You need a workspace or flex space instead of a rental unit.
  • If you are looking for an ADU with a larger kitchen

Design ideas:

  • Swap out the linen closet for more space in the bathroom to fit a tub/shower combo.
  • Add a room divider between the kitchen and living area for more privacy when the living area is used for sleeping.
  • Install a ceiling-mounted curtain rod across the wall from the bathroom to the living room to create a separation
  • Utilize a Murphy Bed in the living space across the wall without windows, allowing space for a sofa against the windows.
ad backyard cottage office wheelchair accessible

About this ADU Plan:

This amazing space is ideal for a private home office, or she shed getaway. This space has very little to offer in the kitchen area but has tons of windows for natural light. The cathedral ceilings make the small space feel even larger. This plan could be a meditation space, spa room, or even theatre room for your backyard.

Square Footage: 298 square foot

Dimensions: 21′ x 16’6″

Architecturaldesigns.com

Who this plan is perfect for:

  • This is a great option if you have a loved one with no specific need for cooking space.
  • You want a spacious private home office from your primary residence with no sleeping space.
  • If a loved one needs an ADA space, this plan offers a roll-in shower and wider doors.

Design ideas:

  • If this plan grabs your eye and you need sleeping space, consider a sofa bed or elevator bed.
  • Add a daybed sofa to add as-needed sleeping space.
  • install a sliding door to the bathroom to allow for storage or a full-length mirror on the back wall of the bathroom
  • Install corner shelves in the corner of the living space to add a storage area.
  • Add shelves at about 7 foot high in the main living space to house decor or plants

About this ADU Plan:

This secondary house has its own garage and more windows than some houses three times its size.

Don’t let this plan scare you off if you only want a ground-floor detached ADU. This plan could easily be adapted to a one-story.

If your area allows more than one ADU on the property, like in California, this is one of the ADU designs that can be adapted to a duplex ADU plan with two rentals.

Square Footage: 418 square feet

Dimensions: 19′ x 25′ 10″

Architecturaldesigns.com

Who should consider this plan:

  • An ADU with garage space could get you more rental income, or if you want your own garage or storage space and the ability to generate rental income on the 2nd story.
  • You have a dream view you want to capture, this plan offers a ton of windows.
  • If you need an ADU with an expansive living space and a ton of natural light, this is your perfect plan.

Design ideas:

  • Take this same plan, make it one-story, and swap out the middle double windows for a set of French doors.
  • Swap the windows behind the bedroom space over to the living room space side so you can install a Murphy Bed or Elevator bed.
  • Use a storage furniture piece between the living and sleeping areas that houses a TV on a lazy Susan so both areas can benefit from it.
  • Take advantage of those windows and install an herb garden nearby for fresh herbs all year.

💡 Common Design Ideas to Maximize Space in an ADU

THE Best ADU Plan with Office Space Under 500 sq ft

A dedicated home office is desirable in any living space. Versatile furniture pieces, such as a desk that transforms into a dining table or a hidden workspace nestled in a closet, offer a harmonious blend of comfort and productivity, all while maximizing space efficiency.

A dedicated workspace is possible even in a space under 500 square feet.

Let’s check out some of the best plans that will allow you to capture some workspace in your ADU plan.

Isla floor plan

About this ADU Floor Plan:

This plan has some great features and is a top plan of choice. The screened porch is a bonus in my eye, but it doesn’t have to be added to the structure.

This ADU plan also has a dedicated bedroom and a 2nd private sleeping space or dedicated office space.

The main living area even offers quite a bit of kitchen counter space.

Square Footage: 393 square feet

Dimensions: 27’5″ x 19′

Pinuphouses.com

Who should consider this plan:

  • If you need a dedicated office space or a 2nd sleeping space.
  • You intend to rent the space to a small family.
  • You want a private space away from the main living area and bedroom.

Design ideas:

  • If you don’t need an office or 2nd sleeping space, turn the extra room into a nice storage closet.
  • A larger dining table could fit if the table had a leaf insert.
  • Opt to install a set of sliding doors between the two sleeping areas instead of having a separate door to the smaller sleeping area
  • Install a barn door to the bathroom and a sliding door to the bedroom to save space.
AD 499 ADU with office floor plan

About this ADU Floor Plan:

This plan with a shed-type roof has a ton of windows to capture a lot of natural light and incredible views.

The bathroom is compact with a two-person shower. The space has two private areas for sleeping or a dedicated office.

The main living area is open and has added windows to increase the natural light pouring in. The porch is a nice addition to provide more usable space.

Square Footage: 499 square feet

Dimensions: 22’4″ x 22’4″

ArchitecturalDesigns.com

Who should consider this plan:

  • If you need a dedicated office space or a 2nd sleeping space.
  • You intend to rent the space to a small family.
  • You have great views to capture.

Design ideas:

  • The office space could double as 2nd sleeping space by adding a Murphy Bed
  • Add a kitchen island on wheels with seating for added functionality
  • Add shelving above the windows on the front of the house to capture some storage space to display items
  • You can install sliding doors to the sleeping areas, bathroom, and laundry nook to save space
  • Opt not to add the porch if it will be a budget buster.
AD Guest cabin with sep living floor plan

About this ADU Floor Plan:

This ADU plan has a shed-type roof, which allows additional windows for natural light.

The main living area is separated into the cooking and eating and then the living area.

This layout offers a little more flexibility in the space and privacy if more than one person lives there.

The small front porch is a budget-friendly addition to create more usable space. The plan offers a small loft over the living area for additional functionality and storage.

Square Footage: 460 square foot

Dimensions: 20′ x 23′

Architecturaldesigns.com

Who should consider this plan:

  • If you want a separate main living area, this plan offers a separate room for the living area.
  • The living area can function in multiple ways, including an office or secondary sleeping space.
  • You want a sleeping loft, a bedroom, and a separate living room space. This plan could have three separate sleeping areas if needed.

Design ideas:

  • Switch out the door to the living room for sliding French doors centered in the opening to have more of an open feel
  • Install a Murphy Bed in the bedroom to capture floor space during the day for a home office.
  • Install some shelving in the corner where the bathroom and bedroom meet to capture some usable storage space
  • Add a fold-down table to the kitchen on the blank wall for as-needed eating space.

➡️ Check out the Design Ideas and Plan Variations I included for this plan. ⬇️

Something about this plan caught my attention because of the flexibility of the layout and how many functions could be stuffed into this small space.

I took the floor plan layout and got to play with my home design software (a guilty pleasure of mine).

giphy

I wanted to see what tweaks I could do to transform the plan into a space for 6 to sleep, an office space by day, and a more open layout in the main area.

Here are my changes and a breakdown of what I would do to transform this plan into an even more flexible design.

The First Floor

The 2nd Story Loft

THE BEST 1-Bedroom ADU Plans

While studios are efficient, a one-bedroom ADU offers an added layer of privacy.

To maximize space, consider designing a compact bedroom with built-in storage and sliding doors.

Opt for an open-concept kitchen and living area, which creates a more spacious feeling and provides opportunities for entertaining guests.

Consider designing a compact bedroom with built-in storage and sliding doors to maximize space

Lori floor plan

About this ADU Floor Plan:

This plan offers a narrow design with two porches. The extra loft provides additional space and function to the plan.

The tall ceilings in the main living area really open up the plan, and the kitchen is efficiently designed. The number of windows in the design captures a ton of natural light.

Square Footage: 317 sq ft

Dimensions: 25′ x 10′

Pinuphouses.com

Who should consider this plan:

  • This is a great plan if you have a narrow lot.
  • If you love really tall ceilings and open spaces.
  • You want flex space in a loft.

Design ideas:

  • Install stairs with drawers in the steps for added storage.
  • Opt for a sofa bed in the living space for an extra sleeping area.
  • Add shelving above the windows in the living room space to capture storage areas for display items.
  • Consider a full wet bath instead of having a shower stall to offer more space for two to shower.
  • A Murphy Bed could be utilized in the bedroom so the space could function differently during the day.
Truoba Mini 117 floor plan

About this ADU Floor Plan:

This plan offers a separate private bedroom space from the main living area. The plan includes lots of storage, including a washer and dryer.

The main living area is spacious and has lots of windows overlooking a large covered porch.

The porch alone is almost as big as the home but doesn’t have to be added to the plan. The bedroom has a set of French Doors to access the porch space.

Square Footage: 500 sq foot

Dimensions: 36’7″ x 10′ (living room is 13′)

Truoba.com

Who should consider this plan:

  • The plan is just calling to be placed near a beautiful view.
  • The private bedroom offers a true getaway because it is removed from the living space. It defines the two functions of the person staying here.
  • If you enjoy a long wrap-around porch, this may be for you.

Design ideas:

  • Opt to not install windows in the kitchen area and instead use them for cabinetry or open shelving.
  • Save money in the budget by removing the two smaller windows in the bedroom.
  • Add a sofa bed to the living space for guest sleeping space.
  • A Murphy or loft bed in the bedroom will provide more usable floor space
  • Add shelves in the corners for decor and knick-knacks.
  • Install a pocket door to the hallway for more sound barriers for the bedroom.
485 sq ft Cabin Retreat floor plan

About this ADU Floor Plan:

This plan utilizes space well and could easily adapted to be wheelchair accessible. The separate bedroom space gives privacy from the open main living. The shed-type roof allows for additional windows to bring in even more light.

Some may want to create a loft space if the roof pitch is slightly modified. The 100 sq ft covered porch offers a nice place to enjoy the outdoors.

This plan only has windows on two sides, so it could offer privacy to structures on the side.

Square Footage: 485

Dimensions: 22’4″ x 26’8″

ArchitecturalDesigns.com

Who should consider this plan:

  • If you have a loved one who needs a separate space that can easily be modified for wheelchair access, this is a great option.
  • Since the kitchen space is smaller, this plan would make a great short-term rental.
  • This plan is great for a flexible main living area with potential loft space.

Design ideas:

  • Consider screening the covered porch for protection from critters.
  • A Murphy Bed in the bedroom will open up the space.
  • The blank wall without windows in the main living areas could house shelving for storage.
  • Consider combining the bathroom and laundry space into one room with a pocket door to open up the entire area and save a little in the budget.
  • There is space for a narrow pantry (~ 6″ deep) in the kitchen on the left side of the closet wall.

Final Thoughts

As we’ve seen, small ADU floor plans under 500 sq ft can be big on style and functionality.

Whether it’s a cozy studio, a comfortable one-bedroom home, a wheelchair-accessible space, or a home with an office, there’s an ADU plan to fit every need.

These designs show that with creativity and smart planning, you can create a space that’s not just a place to live but a reflection of your lifestyle and values.

So, whether you’re retiring and downsizing, providing a home for a loved one, or just looking for an extra income source, these ADU floor plans prove that good things really do come in small packages.

What is the Smallest ADU?

The smallest ADU is 150 square feet in most areas. That could be a space 10 feet by 15 feet. In such a small space, maximizing storage and function are key.

What size should a 1 bedroom ADU be?

An ADU with a true 1-bedroom space will likely be at least 200 – 250 square feet. To be classified as a bedroom, there are minimum size requirements, about 8 feet wide.

Why are ADUs so expensive?

Even in smaller square footage, the most expensive parts are still present, like the kitchen, bathrooms, and windows. Empty square footage is often cheaper to build.

What does ADU stand for?

ADU stands for accessory dwelling unit. These structures are typically added to a property with a primary residence for rental purposes.

How much does an ADU cost?

The cost of an ADU will depend on several factors including, if it is site-built or prefab, as well as the size of the space. The location where you are building will also be a factor.

How do I finance an ADU in California?

The good news is several new finance products were created to help finance an ADU. Check out new ways to finance an ADU.

Can a Tiny House be an ADU?

Maybe. There are requirements for ADUs, and a tiny house on wheels may not qualify legally. Check the local ordinances.

Author
  • Erin Hybart

    Meet Erin, a real estate enthusiast with a wealth of knowledge and an insatiable curiosity for all things Real Estate and living with intention. She passionately advocates for alternative, affordable, and eco-friendly housing solutions. She believes in pushing the industry's innovation boundaries and thinking outside the box. As a licensed real estate agent in Louisiana, Erin dedicates herself to assisting clients in buying and selling properties and mentoring fellow agents to succeed in their own Real Estate businesses. In addition to her professional pursuits, Erin channels her expertise into captivating house-flipping adventures.

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