• Angie Lane

Why Everyone Is Talking About Accessory Dwelling Units (ADU)

Updated: Sep 24, 2021

First off: what are accessory dwelling units? Accessory dwelling unit means: a room or set of rooms in a single-family home in a single-family zone that has been designed or configured to be used as a separate dwelling unit and has been established by permit; a secondary house or apartment that shares the building lot of a larger, primary house.

Accessory dwelling units can be detached from the main residence...

modern house design accessory dwelling unit

Home and studio by In Praise of Shadows

They can be attached as an addition (or as a conversion of part of the original footprint)...

modern house design accessory dwelling unit

Propel Studio

Accessory dwelling units are also popular over garages...

modern house design accessory dwelling unit

You may also know them as mother in-law suites, guest suites, in-law suites, guest house, carriage house, attic or basement apartment.

modern house design accessory dwelling unit

Back yard office by FiveDot

There are several companies that specialize in tiny homes and accessory dwelling units. Some are pre-fab and some are model units...

modern house design accessory dwelling unit

Wishbone Tiny Homes

modern house design accessory dwelling unit

Plant Pre-Fab

But why do accessory dwelling units keep coming up over and over again? You know if Justina Blakeney mentions it, it's going to continue to be a "thing". But it's not just because an amazing entrepreneur/designer is talking about them. Accessory dwelling units have many benefits:

  • Economical Housing for Elderly Parents

  • Increased Home Value

  • Passive Income Opportunity

  • AirBnB Possibilities

  • Economical For Adult Children in Transition

  • Economical Housing for College Kids

  • Economical Way to Downsize a House

  • Easy Way to Create a Home Office or Studio

modern house design accessory dwelling unit

The Biggest Thing to Keep in Mind with Accessory Dwelling Units

Zoning. These are the local laws that dictate the uses allowed on your property. Even though accessory dwelling units are on the rise, there are still many jurisdictions that do not allow a second dwelling on certain properties. That's not to say you still can't have one if it's not allowed in your zoning but it does mean additional costs to file for a variance with no guarantee it will be approved.

Every jurisdiction also varies as to what they define as an accessory dwelling unit as well as different restrictions they put on accessory dwelling units. For instance, I had one jurisdiction where just the installation of a dishwasher in a garage studio constituted an accessory dwelling unit even though there was no intent to have an occupant in the space. It was purely for the homeowners. Some jurisdictions interpret any additional kitchen features (stove, dishwasher, etc) to constitute an accessory dwelling unit. Sounds crazy but it happens.

The best thing to do is to either contact your zoning official right from the beginning and if you've hired an architect, this will be the first thing they do as well. They probably even have a relationship with local officials so it's worth it to hire them to do the initial digging, even if you don't hire them to complete the design and drawings.

Also, if you are in a subdivision or other neighborhood with an association, they may have their own set of rules and guidelines for accessory dwelling units.

Economical Housing for Elderly Parents

Improvements in medicine and healthier lifestyles have lead to longer lifespans. This means there is a large segment of the population that is elderly. "The number of Americans ages 65 and older is projected to more than double from 46 million today to over 98 million by 2060, and the 65-and-older age group's share of the total population will rise to nearly 24 percent from 15 percent."-prb.org

The hallmark of accessory dwelling units in modern house design is efficient and small floor plans. This is especially key for elderly people looking to scale back. The need for accessibility and compliance to handicap standards should also be taken into consideration for elderly occupants.

modern house design accessory dwelling unit

Besides an efficient and smaller floor plan, another nice feature of accessory dwelling units and modern floor plans is the accessibility to a covered, exterior space.

modern house design accessory dwelling unit

The need for affordable housing is already here and only going to get bigger. Accessory dwelling units are an economical solution to this problem.

If elderly parents are still active, accessory dwelling units are a great way for them to maintain their independence while at the same time be in close proximity to relatives in the event that they need help. The smaller sized home also reduces the size of things they need to take care of. Having a home that's too big for them to take care of any longer can be a point of stress, especially if they can't afford a smaller home. An accessory dwelling unit on a child's property eliminates this stress and depending on local real estate, is often much cheaper than buying a smaller house or condo. An accessory dwelling unit is also an investment as in most areas it adds value to a home versus even the option of renting an apartment.

modern house design accessory dwelling unit

If an elderly parent needs a level of in-home care, accessory dwelling units are also an economical solution to that. It eliminates the cost of an "old folks home" as well as allowing the occupants to be close to family without being in an institutional setting.

The issue of aging relatives can bring up lots of emotions. The parent(s) feeling like a burden. The children feeling guilty or even helpless when it comes time to try to make decisions for a parent. Oddly enough, the accessory dwelling unit can help alleviate some of those feelings and actually be a mutually beneficial situation. The parent using money that may have went to buy a condo and instead constructing an accessory dwelling unit on their child's property, gives them a sense of control and, more importantly, a feeling of being helpful instead of a burden. They are investing in their children's home, which benefits both them and the children.

Increased home value

This is a tricky one to throw out there as a generalization but as their popularity rises, an accessory dwelling unit becomes a more desirable feature in contemporary homes and modern design. Across the board, it seems that property values go up with an accessory dwelling unit but this is definitely specific to the market in that area. Areas that already have a pretty good density of homes tend to have a better return on investment. So urban and suburban environments tend to fare well.

modern house design accessory dwelling unit

modern house design accessory dwelling unit

small but very comfortable living space

This article is very informative as to how accessory dwelling units are appraised. This article mentions the fact that accessory dwelling units can also be used for passive income, which also affects the return on investment.

Passive Income Opportunity

An accessory dwelling unit can provide passive income when used as a rental unit. There is almost always a need for affordable housing. The smaller footprint and amenities of an accessory dwelling unit lend themselves to providing an affordable rental option.

Things to consider modern home design, accessory dwelling units, and passive income is whether or not to have an attached or detached accessory dwelling unit. You may not have a choice, depending on your zoning or your lot, whether you can have an attached or detached accessory dwelling unit. If the only way is to have an attached accessory dwelling unit, use special considerations when it comes to insulation, sealants, and sound proofing. The detached accessory dwelling units require special consideration when it comes to cars and parking. This may also be a separate (prohibitive) zoning issue so be sure to CHECK YOUR ZONING!

Check out this article for elaboration on attached & detached, as well as more benefits of accessory dwelling units. However, please note the costs listed in the article seem to be out of date. Always consult a local contractor to get the best idea of costs. And the only way to get a hard and fast cost is to have drawings. So contact an architect- like me!

modern house design accessory dwelling unit

AirBnB Possibilities

The popularity of AirBnBs has also led to an increased popularity in accessory dwelling units as well. This is also another method of passive income. AirBnBs allow for more flexibility in terms of how long an occupant will be there. You can control when the unit is available to rent.

modern house design accessory dwelling unit

AirBnB in Austin, TX

AirBnBs invite creativity in terms of ways to draw renters in as well. You can be completely fun or themed to offer your accessory dwelling unit as a unique space. With the popularity of eco-tourism and agro-tourism, accessory dwelling units make a lot of sense.

modern house design accessory dwelling unit

Bungalow in Maui

For eco-tourism, the tree house or zero footprint trend is a great way to build compatibly with the environment. Accommodating groundskeeping equipment and sleeping quarters alike, this enchanting little abode affords an ideal natural interconnectedness for its user

modern house design accessory dwelling unit

Garden Shed by Ville Hara.

This one from Gather Greene has "all the comforts of a tiny hotel room, in the middle of the woods. With a grand picture window, you will feel like you are out in nature, but with air conditioning, heating, and warm showers, you will be able to enjoy it like never before. Each one of our seventeen cabins comes with an outside deck, a king size bed, bathroom, closet with large mirror, mini fridge, and caffeine fix."

modern house design accessory dwelling unit

modern house design accessory dwelling unit

And this amazing cabin: "Principal designer Tom Kundig, of Olson Kundig Architects, developed the structure for a client who fly-fishes on the Olympic Peninsula. The owner wanted a “compact, low-maintenance, virtually indestructible building to house himself and his wife during fishing expeditions.” Stairs lead up from outside and into to the house, which consists of two levels. The entryway, dining area, and kitchen are located on the first level while a sleeping loft is located on the upper level. An outdoor deck also provides a view of the river."

modern house design accessory dwelling unit

There is also a rise in "glamping" (glamorous camping). Small, luxurious tent spaces that cater to those who would probably never even think about camping. Some are more elaborate than others and are basically a hotel room in the wild.

modern house design accessory dwelling unit

Accommodations at Collective Hill Country, a Retreat at Montesino Ranch, outside Austin, Tex.

This one might not exactly be "glamping", but it is definitely in the middle of nowhere and surrounded by nature. I would glamp here any day.

modern house design accessory dwelling unit

Casa Tiny, Puerto Escondido, Mexico

Economical for Adult Children in Transition

All the millennial jokes aside, there is a large population of young adults who either cannot afford housing on their salaries or are just barely making ends meet and living paycheck to paycheck. It's not due to laziness or lack of ambition. Today's economy has a vastly smaller middle class, an large, college educated young adult population with hefty student loans, and very few jobs that pay enough to live beyond paycheck to paycheck, even with a college education.

modern house design accessory dwelling unit

Second story accessory dwelling unit by Peterssen/Keller Architecture

Tiny house architecture is perfect for a modern home design that needs an accessory dwelling unit.

modern house design accessory dwelling unit

Micro House by Fieldwork Design & Architecture

Many of these young adults are forced to rely on mom and dad. An accessory dwelling unit is an economical solution to this problem. It gives separation between parents & children while allowing the children to save money (assuming parents aren't charging rent or charging a highly reduced rate). Saving money is so hard to do today. This bit of savings by "living at home" can allow kids time & stability to seek out higher paying jobs and actually have a chance of taking on the leap of sustaining themselves on their own.

Prefab accessory dwelling units might make sense for contemporary homes that need an accessory dwelling unit.

modern house design accessory dwelling unit

the Eco Pod model by Pod Space

When the children leave, the parents are left with an accessory dwelling unit that can provide additional income as an AirBnb or as a rental housing unit. Or, once the kids are gone, maybe grandma & grandpa will need a place to live that offers closer proximity.

modern house design accessory dwelling unit

a one-bedroom house designed by Glamuzina Paterson Architects

Economical Way to Downsize a House

Many people are finding that they simply don't need the size of house that they used to. Whether they are empty nesters or simply trying to scale back day to day responsibilities, many people are starting to downsize.

modern house design accessory dwelling unit

Detached accessory dwelling unit by Robert Hutchison Architecture

One way to downsize, without buying a new house, is to convert part of your existing house into an accessory dwelling unit. You downsize what you already have while at the same time creating a passive source of income. You get all the benefits of downsizing without having to move.

modern house design accessory dwelling unit

Granny Flat by Hyer Architecture

Of course all the normal market factors figure in to just how economical this can be, but the other benefit of converting a portion of your existing house into an accessory dwelling unit is that in some areas it can be hard to sell houses with large square footages. The vast McMansion floor plans have fallen by the wayside in terms of popularity but there are still many of those types of houses out there. Converting these older plans into modern floor plans containing an accessory dwelling unit can increase the home's value.

modern house design accessory dwelling unit

800 square foot house by Webster Wilson

I have done several accessory dwelling units, each with their own unique set of complications. You can do accessory dwelling units attached or detached. They can be part of your house remodel or part of your new build modern house design. Construction costs vary. Please contact local contractors to get ideas about pricing. The way to get the most exact price is to go to the contractor with design drawings in hand. This is where an architect can help.

If you're not sure what to do with soon to be displaced family members or wouldn't mind the opportunity for extra income, an accessory dwelling unit could be the answer. I can help you determine if it's the right answer as well as get you an efficient, contemporary design so you'll have all the drawings you need to approach contractors as well as city officials.

modern house design accessory dwelling unit

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