What is an "ADU"?

Many people are acquainted with and can identify a “two family” home. A two-family home is typically a house that is divided either vertically and designed for two families to live side by side (also known as a “Duplex”) but separated by a party wall (a shared or common wall) or, divided horizontally and designed for two families occupying separate apartments constructed one above the other (known commonly as a “two-family”).

A two-family or duplex style home provides the opportunity for extended family members to live within proximity of other members of the family or can be owned as an investment option for property owners.

Are ADU's New?

An extension of the model of a two-family or duplex style homes is an “ADU” or accessory dwelling unit. If you have never heard of the term “ADU” previously you may be acquainted with the more commonly known terms such as “in-law suite” or “mother-in-law suite or apartment”, “accessory apartment”, “multi-generational unit”, “second unit” or “granny flats” (There may be some people who object to the term “granny flats”. In the research I have done for this article, I was unable to discover historical evidence to support the suggestion that this term has disparaging origins.). These terms all apply to the same idea of an “ADU”.

For simple explanation, ADU’s are supplementary living quarters on single family homesites. They are designed to function autonomously of the primary or single-family home. They are designed with fully functional kitchens and baths. An ADU can be designed with additional rooms such as a sitting room.

The idea of an ADU is not new. The history of ADU’s can be traced to the early 20th century. After World War II, America discovered the suburbs. At this point in time local municipal zoning adopted a system that created districts which allowed for the development and construction of single family, two family and multi-family homes, together with areas which permitted the development and construction of commercial, industrial, office and retail businesses.

As the suburbs continued to flourish, the elevated demand for lower density construction was a significant factor which contributed to many local municipalities to exclude the construction of ADU’s.

There have been many clients I have represented in my career who owned properties containing an ADU which are commonly categorized as “in-law apartments” or “in-law suites”. Some of these in-law apartments were not officially recognized by local zoning, while others were allowed through “spot-zoning”. In the cases where the properties were sold to buyers who financed their purchase through the traditional means of mortgage financing and, the local zoning did not allow for such an ADU, the mortgage lender, as a condition of the purchaser’s loan commitment, would require the second kitchen found in the in-law apartment to be removed prior to the closing. The expense of which was often fell to the seller of the property in cases which the buyer was hesitant or unwilling to perform demolition work on a property they did not yet own.

The Different Types of ADU's

An ADU can either be attached to the primary single-family home or detached from it. ADU’s are typically smaller in stature compared with the primary residence, but they can become a second source of income, or a circumstantial convenience designed to keep a compassionate eye on extended family or a loved one.

ADU’s can also serve as home offices, guest quarters and, in some cases where local zoning permits, short term rentals.

There are five different types of ADU’s which can be grouped into three categories: Interior, attached and detached.

Detached (New or Existing) Construction: This would be a standalone ADU and separated from the primary residence which may be described as a “rear yard cottage” or a “garden cottage”.
Attached Addition ADU: This ADU would be a new construction addition to the existing primary residence.
Attached (or detached) Above Garage ADU: Occasionally, an ADU can be added on the second floor above an existing attached or detached garage with relative ease.
Attached (or detached) Garage Conversion: In this example, the function of housing an automobile or storage space is converted in favor of an ADU.
Basement Transformation to an ADU: This option converts existing basement and storage space to living space for an ADU.

Some Important Items to be Aware Of

Local zoning laws can vary from one town, city, and village to another. Check with your municipal building or zoning department to find if the local zoning law permits an ADU on your property. Ask if there is a minimum and/or maximum size of an ADU, if allowed.
If the local zoning law or ordinance does not allow for an ADU, it may be possible to secure a variance.
Some local zoning laws do not allow full kitchens in ADU’s while other may not allow such suites to be rented out.
With a growing need for affordable housing and the increasing frequency of adult children providing elder parent care, some states and local municipalities have structured zoning laws in such a way which promote the use of ADU’s.

The features, general accessibility, and conveniences of an ADU can make a home more desirable and, thereby, more valuable to certain prospective home buyers. Multi-generational living has been on the rise for several years. Finding a single-family residence with an ADU can be enticing for homebuyers looking for that benefit.
The ADU is part of the primary residence. Therefore, the ADU cannot be sold separately from the primary residence.

How Should an ADU be Designed?

I represented a property owner who sold a primary residence with a garden cottage ADU. In speaking with several prospective buyers, a floor plan which was “open” was of primary importance as was 36-inch doorways. Having kitchen and bathroom space that is ADA enabled is another feature which enhances the salability and usability of the ADU.

The primary disadvantage to constructing an interior ADU may be the loss of storage space. Yet, most homeowners I have spoken with cite the advantages of an ADU outweigh the relative brief list of disadvantages. In both the short and long term, an ADU may be a wise investment both while living in the home and when it comes time to sell the property.

If you have questions about ADU’s or any other real estate related topic, please click the “contact me” button.