What are ADUs?

By‌ ‌Ashley‌ ‌Zimmermann,‌ ‌Creative‌ ‌Content‌ ‌Director‌ ‌for‌ ‌@designREMODEL‌ ‌

Have you ever heard of a mother-in-law suite or a granny flat? The image that often comes to mind is of a separate apartment or section of the house for one’s aging parents or in-laws as they move in with their adult children. The official term for this living situation is an accessory dwelling unit (ADU).

ADUs Explained

Travelers tells us: 

“A ‘granny flat’ is an accessory dwelling unit (ADU) attached to your home or free-standing on your property. Also known as an in-law suite, mother-in-law suite or a garden cottage, a granny flat serves as a self-contained living area.”

As mentioned above, an ADU is considered a self-contained, full residential unit, not merely a separate building, like a shed, for example. Clever quotes the American Planning Association: “An accessory dwelling unit (ADU) is a smaller, independent residential dwelling unit located on the same lot as a stand-alone (i.e., detached) single-family home.” An ADU can also be called an accessory apartment or a secondary suite, and more.

Building

Be prepared to spend a tidy sum if you plan to go the building route. Clever reminds us that since an ADU is considered a full residential dwelling, you’ll need to include plumbing and appliances as well as décor. Check out this interesting ADU cost calculator for examples of cost in San Mateo County, California. New construction and modular are two building options, the modular method being built offsite and delivered to your location. Modular fabrication can be significantly less expensive than a new construction.

Getting Started

As with any residence, there are rules and codes to be followed. Check out the below linked “Guidelines for Garage Conversion ADUs” for the state of California. Mass.gov says that often owners do not follow zoning guidelines, so their ADU is ‘unlawful’; we definitely don’t want that, so call to schedule an appointment at your local zoning office. The League of Wisconsin Municipalities explains in their article titled “Accessory Dwelling Units: A Provocative Alternative to Traditional Housing”:

“ADUs are not defined in or directly regulated by state law … [therefore] the lack of statutory direction provides municipalities significant leeway in defining and customizing ADU regulations to meet the needs of a specific town, village, or city."

Upon doing some searching, I quickly found a Facebook page called “ADUs in Madison & Dane County, WI.” Ample resources are available; just do your research.

Converting

Escape to the Chateau on PBS has been parents’ guilty pleasure 'quarantine' show over the last two years, and I remember watching a specific episode with them that featured the owners converting their 19th-century French chateau’s old tack room into a beautiful granny flat for Angel’s mother. The before and after pictures are amazing. 

Not many of us have a French castle property to renovate, so your conversion will likely look more like converting a pool house, garage, finished part of the house, or unfinished part of the house.

Renting out

ADUs are not only for aging parents! I see essentially limitless potential for renting an ADU in this age of Airbnb. New Avenue, a West Coast design and building firm that specializes in ADUs and compounds, agrees you can take the short-term Airbnb approach or consider renting your ADU on a long-term basis. They showcase a handy chart on their site to help you decide what route might be the best for your needs, considering the factors of turnover, privacy, and amenities. For example, you may want to consider how much privacy your dwelling offers: if you plan to rent your ADU as an Airbnb property, you will likely opt for more privacy, since short-term vacationers usually prefer a private escape; whereas, if you are renting your property on a long-term basis, you may choose to develop a friendly relationship with your renters. 

If an accessory dwelling unit investment is speaking to your heart, make sure to follow the proper regulations for the area where you live. Then enjoy the creation process and the finished result!

References: 

https://www.planning.org/knowledgebase/accessorydwellings/ - Accessory Dwelling Units

https://accessorydwellings.org/what-adus-are-and-why-people-build-them/ - Accessory dwelling units: what they are and why people build them

https://www.architecturaldigest.com/story/accessory-dwelling-unit-housing-of-the-future - The Ins and Outs of ADUs
https://www.ally.com/do-it-right/home/whats-an-in-law-suite/ - In-Law Suites: More Room for Mom and Pop

https://www.moving.com/tips/what-is-a-mother-in-law-apartment/ - What Is a Mother-In-Law Apartment & Should You Have One?

https://www.masterclass.com/articles/mother-in-law-apartment-guide - Mother-In-Law Apartments: Pros and Cons of In-Law Suites

https://www.travelers.com/resources/home/insuring/insuring-granny-flats#:~:text=A%20%E2%80%9Cgranny%20flat%E2%80%9D%20is%20an,a%20self%2Dcontained%20living%20area - What is a ‘Granny Flat’?

https://www.appraisalinstitute.org/accessory-dwelling-units-may-have-higher-values-when-using-income-approach-the-appraisal-journal/ - Accessory Dwelling Units May Have Higher Values when Using Income Approach: The Appraisal Journal

https://www.newavenuehomes.com/ 

https://www.newavenuehomes.com/blog/adu-design-considerations-for-short-term-airbnb-vs-long-term-rental - ADU design considerations for short-term (Airbnb) vs long-term rental

https://www.hcd.ca.gov/policy-research/accessorydwellingunits/docs/guidelines%20for%20garage%20conversion%20adus%20-%20v6hb%20ada.pdf - Guidelines for Garage Conversion ADUs

https://www.mass.gov/service-details/smart-growth-smart-energy-toolkit-modules-accessory-dwelling-units-adu - Smart Growth / Smart Energy Toolkit Modules - Accessory Dwelling Units (ADU)

https://www.planning.org/knowledgebase/accessorydwellings/ - Accessory Dwelling Units

https://calculator.secondunitcentersmc.org/ - Accessory Dwelling Unit Calculator
https://www.dailymail.co.uk/femail/article-7771513/Escape-Chateau-sees-old-tack-room-transformed-beautiful-grand-entrance-way.html - Escape to the Chateau viewers praise Angel and Dick for transforming an old tack room into a 'beautiful' grand entrance way - by adding a bespoke hand built staircase and upcycling 19th century features

https://lwm-info.org/DocumentCenter/View/3920/4-20-The-Municipality-More-Housing - Accessory Dwelling Units: A Provocative Alternative to Traditional Housing