The Rising Popularity of Accessory Dwelling Units Part 2: Are Homeowners and Localities Frenemies?

By Karen Strong

In Part 1 of our blog series focusing on Accessory Dwelling Units, we discussed the ins and outs of what defines an ADU.  Many homeowners are seeking to add this new type of housing to their property for a variety of reasons, including adding living quarters for an aging relative or a child returning home, creating the proverbial “man cave” or “she shed,” or as an additional source of income. However, homeowners starting their building process may find that local zoning and municipal regulations can pose a set of challenges unique to ADUs.

As the demand for these alternative housing options have increased, so have the number of jurisdictions that are endeavoring to ease regulations. There is, however, no universal ordinance outlining regulations for ADUs, and zoning rules can vary widely from municipality to municipality.

Types of ADUs (Accessory Dwelling Units) currently on the market

Laws Vary From Place to Place

An analysis conducted by the New York Times’ The Upshot found that a large number of cities have laws making it illegal to build anything other than a detached single-family home on 75% of residential land. In Charlotte, NC, the law is even more strict, with 84% of residential land zoned solely for Single Family homes.

Each jurisdiction will most likely have passed its own ordinance outlining the regulations for these units. If not, state law must be followed. The ordinance will often include specific regulations for things such as:

  • Parking
  • Maximum unit size
  • Able to rent long or short-term (i.e. Airbnb)
  • Whether owner occupancy is required


One County Debates the Issue

The Montgomery County Council Debating a bill that will bring ADUs to part of the county

In 2019, ADUs were actively debated in Montgomery County, Maryland when councilman Hans Reimer introduced a bill easing requirement for the construction of ADUs.

Residents were worried about overcrowding and the destruction of neighborhood character.  According to Montgomery County Executive Marc Elrich, “As I've indicated, I believe it is important to establish a responsive, well-regulated, and fair approval process for ADUs for property owners seeking alternative housing options, whether to address multigenerational needs or generate a source of income to provide mortgage relief or allow seniors to age in place. However, this is not a "one-size-fits-all" County, and how we achieve these goals matters if we want to successfully integrate a larger number of ADUs into our single-family neighborhoods.”

After much discussion, Maryland’s Montgomery County Council unanimously passed a bill allowing accessory dwelling units in three of the county’s residential zones. The bill, Zoning Text Amendment 19-01, would loosen restrictions for in-law suites and tiny homes, and allow homeowners to convert basements and garages into separate residences.


A brochure by the Town of Ridgway, Colorado spells out some of the things residents need to know when considering building an ADU

ADU Facts and Figures

Counter to the concerns of some residents, research by does not support fears about lower property values or parking shortages. Conversely, there are some indications that ADUs do increase the supply of affordable housing and do make significant economic contributions to their host communities through construction activity and property taxes.

While land use in the United States is usually legislated by local governments, occasionally there is a mechanism that allows the state to provide input. The New Hampshire Home Builders Association was a vocal advocate with a coalition, including Housing Action New Hampshire and New Hampshire's Business and Industry Association on this issue, and in 2017 New Hampshire passed an ordinance that requires local zonings to allow ADUs nearly everywhere that single-family houses are permitted. The New Hampshire law also prohibits some of the most commonly restrictive regulations including requiring that the units have fewer than two bedrooms, be smaller than 750-square-feet, or that a person related to the owner live in the ADU.

California has continually taken steps to encourage and support the option for building ADUs. Effective January 1, 2018, California enacted legislation that allows ADUs to be built alongside a primary single-family residence along with an easing of parking restrictions and fees from utilities.  The city of Los Angeles currently has over 1,000 ADUs.


Check Out the Twin Cities

Sometimes even cities in the same metropolitan area utilize different strategies to adopted ADUs. For example, in Minnesota, Minneapolis and St. Paul may be called the “Twin Cities,” but they have taken very different approaches as to how they regulate ADUs.

Since 2013, both Twin Cities have explored how to increase diversity and add density in residential neighborhoods. In 2014, Minneapolis introduced an ordinance to allow all types of ADUs—internal, attached, and detached—to be built on single- and two-family lots throughout the city, resulting in the issuance of 92 building permits in the first three years.

Conversely, beginning in 2013, St. Paul took a more incremental approach via a pilot ADU program near its Green Line light rail.   After public input and review, a 2016 zoning ordinance established the total area permitted for ADUs in an area of just 3.5 square miles.  Due to these neighborhood limitations, unlike Minneapolis, only one ADU was permitted for construction within the first year.


And in the Northwest…

The cities of the Pacific Northwest, particularly Portland, OR, have led the way in ADU innovation. A survey and study completed by UC Berkley entitled, Jumpstarting the Market for Accessory Dwelling Units: Lessons Learned from Portland,Seattle, and Vancouver details their challenges and successes.

As Portland based ADU consultant Kol Peterson points out, “There’s the potential for ADUs to create a lot of affordable housing, but it’s going to take decades. ADUs are still in their infancy. Only four cities in the country — Portland, Los Angeles, Seattle and Austin, Texas — have more than 1,000 ADUs.”


Summing It All Up

Many cities and counties permit ADUs in single family neighborhoods, subject to several common requirements, including limitations such as owner occupancy, lot size, and number of bedrooms. Some of the most restrictive challenges for those homeowners seeking to rent their ADUs for supplemental income are those communities that limit ADU occupancy to family members.

As communities strive to expand housing options for their citizens via ADUs, most municipalities will find that permitting them is not as easy as flipping a switch. Instead, each community will need a long-term strategic plan combined with assessments, demographic studies, and the drafting of specific zoning regulations.  These studies often uncover illegal ADUs in older communities. Sometimes as part of the overarching plan, an amnesty period will be granted contingent upon the owner registering the illegal ADU.

Together, the studies we’ve seen focusing on ADUs spotlight the need for more affordable housing and resources for senior citizens seeking to “age in place.” At Immersion Active, our team will be keeping a close eye on new regulations and studies about ADUs as they become available. If you are a builder or developer interested in learning more about ADUs, we encourage you to contact with our team of professionals for help navigating the rules and regulations in place wherever you are interested in building.

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