Mother In Law Units Make Sense in California. Here’s 6 Reasons Why.

In response to the current housing market, homeowners in California are looking for other construction options; leading to the increase in mother in law units.

Mother in law units, also  known as accessory dwelling units (ADUs), granny flats, secondary units, or granny cottage have been around for awhile; they were popular throughout the early 1900s.

Such add-on spaces fell out of favor shortly after WWII but are experiencing a resurgence during the past few decades in response to a tight housing market coupled with population growth, stagnant economy, and increased focus on environmental concerns.

The housing market is seeing a decrease in the number of available existing single-family homes with simultaneous increases in purchase price. Additionally, more people than ever are looking for reliable housing, most facing some degree of economic pressure.

These factors lead current homeowners to seek ways to earn extra income to decrease their expenses, and potential buyers to search for new housing options.

These units fit into this unique situation to solve many of the economic and physical constraints faced by individuals and municipalities exploring inexpensive housing options.

Put simply: mother in law units just make sense.

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Benefits of Mother in Law Units

Mother in law units offer benefits to the owners of the primary residence, residents of the individual ADU, and to the environment in general.

1. Ease

Accessory dwellings are relatively easy to permit and construct as compared to other housing solutions.

They’re generally not subject to the same building ordinances, zoning laws, or impact fees as single-family homes. And they require much less time to build on the premises.

2. Amenities

Residents of ADUs enjoy the amenities of living in a neighborhood without the major investment; and the perks of apartment living without the impersonal quarters.

Mother in law units offer more privacy, parking, and yard space than an apartment but residents can escape the lawn work and property maintenance that accompanies home ownership.

3. Keeps Character

Small residences like these add living space to a neighborhood without changing the character that comes from its current structures.

Most ADUs aren’t obvious as someone drives by the main residence; they’re not an eyesore or blight to the nearby architecture.

4. Environmental Footprint

Accessory dwellings leave a smaller environmental footprint because of their size. They require less space, energy, and materials to construct.

Less existing land has to be altered at their location, and they require less energy to heat and cool the facility.

5. Additional Income

Renting the additional space afforded by the ADU brings in additional income for the homeowner.

The prevalence of online tools makes it easy to find a reputable long-term or short-term tenant. The extra space also increases the overall property value.

6. Cost-Effective

Accessory dwellings are a cost-effective alternative to senior living facilities or older children.

Semi-private facilities and adjustments are expensive and out of range for most families. ADUs give your senior or young adult a degree of independence but keeps them close in the event of an emergency or illness.

Current Realities of ADU Home Construction

It’s easy to find studies and research that discuss the theoretical results.

They explore short-term and long-term of citywide implementation of mother in law units and ADUs. However, there’s not much in regards to the reality of what happens to an area when building and using accessory dwelling units.

It’s difficult to conduct studies or find current data because although individual homeowners have, for decades, built such additions to satisfy personal desires and needs, these structures haven’t been widely adopted.

No centralized organization oversees their creation or development.

In most areas, homeowners construct them without obtaining a local permit so data concerning characteristics such as their prevalence, size, and safety simply don’t exist.

The same is true for looking at trends about their ultimate use or how much money comes from them; few people acquire business licenses so little data is available from those local regulatory departments.

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Where Are ADUs Being Adopted?


Some areas, such as Portland, Oregon have embraced ADUs though, and gives us a picture of how these structures really affect the area.

In March 2018, 2000 ADUs were reported. The city building department notes that it issues permits at a rate of about one per day.

Findings in a 2018 report by the Institute for Sustainable Solutions at Portland State University found that the majority of ADU owners have owned their main home for over five years and built the ADU to be used as short-term rentals through companies such as Airbnb.

The large percentage of guests stay 1 to 3 days though a significant amount stay up to a week.

These structures are typically between 700 and 800 square feet, and nearly 85% were constructed by a contractor. Respondents reported satisfaction with the building process, and being a landlord.

Cost of living is the biggest reason for deciding to move into an ADU.


California has also recently reduced regulations governing ADUs in the form of easing the permitting process and changing the requirements for parking spaces.

Researchers at University of California Berkley’s Terner Center for Housing Innovation report a jump in applications though cost is still the largest barrier to construction.

Those researchers also found that most of the units are rented below market value. This is mainly because of their size and the fact that homeowners rather than development companies build them; which makes them comparable to subsidized affordable housing.

Initiatives in Oregon and California to adopt mother in law units is still new, so their impact is changing.

Early indications reveal that they’re not detrimental to the areas where they’re located. Thus far response to them has been positive with no interference of local traffic or crime.


Mother in law units, or ADUs, can’t seamlessly or completely solve all of the economic, environmental, and family issues that arise because of urban development, but they are a step in the right direction.

They solve the biggest problems currently plaguing the housing market, as well as the people and areas affected.

Mother in law suites benefit the individual user as well as the surrounding city.

Individuals enjoy extra income, and tax advantages while government officials are provided a viable way to safely house more people without changing the character of a neighborhood or increasing the environmental burden. Widespread adoption within cities is slow but so far results are promising.