Using accessory dwelling units to bolster affordable housing

Accessory Dwelling Units, such as this one in Northern California, can provide affordable housing and rental income for homeowners. Photo via Forbes.

Creating affordable rental housing in a community is often a long and arduous process. One strategy cities can use to combat this is allowing the creation of Accessory Dwelling Units (ADUs) through amended zoning codes. ADUs, also known as “granny flats,” are small apartments built on a property with a preexisting home as the primary structure. Units typically function as studio apartments and tend to accommodate one or two people. ADUs can allow for seniors to age in place, provide homeowners with extra rental income, and fill a gap in affordable rental units.

An ADU can be constructed as either an interior, attached, or detached unit. Interior units are located within the primary structure, attached units are connected to the primary structure, and detached units are separate—for example, being built above a detached garage. The attached and detached units, which are visible on the exterior of the house, are typically designed to blend in with the primary structure and neighborhood architecture. Allowing for the construction of ADUs offers an alternative to rental projects that would create large and expensive buildings, altering the characteristics of a neighborhood.

Resistance to ADUs often centers around worries about overcrowding a neighborhood with an influx of renters, density, and traffic. In practice, these worries are generally unfounded, because of the practical limitations of ADUs and regulation measures passed by cities. Below are two examples of cities that have decided to allow ADUs under their zoning codes. Santa Cruz, CA has been successfully implementing ADUs for the past decade, and under the guidance of Local Leaders Council Member Lisa Bender, Minneapolis recently passed an ordinance to allow ADUs.

Santa Cruz, CA
Technically, Santa Cruz has allowed ADUs in its zoning code since 1984, but an update in the early 2000s revived the practice in the face of steep housing costs. Retirees on fixed incomes were moving out of the city ,and citizens looking to rent often turned to informal arrangements in undocumented makeshift guesthouses invisible to safety authorities. The zoning code’s rewrite expanded the locations in which ADUs were allowed to include all single-family residential lots greater than 5,000 square feet.

ADUs in Santa Cruz are constructed and permitted along the same standards as primary residential structures. As part of their design, ADUs must be compatible with the primary structure, maintain the privacy of neighbors, and include an off-street parking space. The policy won the “Policies and Regulations Smart Growth Achievement Award” from the U.S. Environmental Protection Agency in 2004.

The city has tried to encourage ADUs through incentives and less restrictive regulations. Homeowners constructing ADUs have the ability to have their permit fees waived if they commit to renting their unit to low or very-low income tenants. Easing the parking requirement, which can act as a barrier to construction, is something the city is looking into to encourage construction. In the decade since the code has been rewritten, over 220 new units have been constructed compared to just 120 in the previous 20 years.

Minneapolis, MN
On December 5, 2014, the Minneapolis City Council voted 10-1 approving an amendment to the zoning code, which would expand the ability to build ADUs from one pilot neighborhood to any lot with single or two-family homes. The amendment, introduced by Council Member Bender, will be able to address some of the housing needs in the city. “The great thing about this ordinance is that it really fits people at all ages and different life points,” said Bender. “It creates more affordable rental options in the city, and rental income can help homeowners stay in their homes.”

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A rendering of an attached ADU. Image courtesy of City of Minneapolis.

The amendment allows all three types of ADUs – internal, attached, and detached – but has regulations that mitigate impact on the neighborhood. Units cannot exceed 1,000 square feet, must be shorter than the height of the primary dwelling, the primary exterior materials of attached units must match those of the primary structure, and exterior materials of detached units must be durable. Two unique features of the amendment are a homestead regulation that requires the property owner live in the primary structure or ADU, and the omission of the parking requirement. These prevent neighborhoods from losing the social fabric of the original homeowners, and avoid the increased congestion from additional automobile traffic.

The amendment passed quickly, and with broad support, in part due to extensive public outreach and coalition building in the city. Six public meetings were held in order to inform citizens and answer any questions or concerns they may have had. The measure was also supported by many advocacy groups. “We were able to put together a great coalition of supporters from the environmental, smart growth, preservation, and senior advocacy communities, which I think really helped build support,” Bender said. She believes that the first ADU projects will come on-line in early 2015, and has city staff working to put together a manual for citizens as well as other outreach events.

ADUs are just one policy featured on the Local Leaders Council Model Policies page. The model policies are used to provide examples of thoroughly vetted policies that leaders can use as templates for legislation in their own towns. Recently, two dozen model policies were rolled out in the categories of housing, transportation, economic development, and sustainability.

Local Leaders Council