Dense Single Family The most common sense of the word “density” in land-use terms is simple: more people in a smaller area. Frequently the only way to accomplish this is to build taller, multi-unit buildings. High rises.

But in areas with low concentrations of people, increasing density can mean something different than building up to the sky. There are ways to create more diversity and choice in single-family neighborhoods—accessory dwelling units (ADUs) can mean mother-in-law apartments, garages converted into detached housing, or rooms for rent. All of these are good growth strategies for cities, providing families and property owners with more options, and maintaining the character of some single family neighborhoods.

There is a lot going on in the region when it comes to increasing choices in single-family neighborhoods. Vancouver, Portland and Seattle are all looking at ways to accommodate more people, while keeping established neighborhoods intact. Each city has a different name and a different game plan to legalize ADU options that have been shut out by city codes, but in all, density is on the rise—and not the high rise.

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  • Vancouver and Seattle have both created programs to legalize the accessory dwelling unit.  ADU’s typically come in two types, attached and detached. In Seattle the attached ADU has been allowed for some time but the detached version has not been, even though many people have had garages or carriage houses they have converted.

    In Vancouver ADUs are called laneway housing, and the city is holding a series of public meetings this summer, beginning on July 21, to consider different options. The laneway program is part of the EcoDensity initiative which I wrote about earlier. Vancouver is proposing to permit the units on lots that are 33′ and wider, lots with an open lane or alley, or a corner lot with an alley. The new unit cannot be built on a lot with a house that already has an existing ADU. The laneway houses can only be rented, not sold. In this sketch the green building is where the city proposes these homes could fit in single family neighborhoods:

    ADU Laneway Housing

    Seattle is also convening some meetings this summer about expanding their Backyard Cottage Housing program. Cottages, Seattle’s name for detached ADUs, are currently allowed in the southeast section of the city. Less than two dozen have been built. The City’s proposal is to expand the program citywide, allowing 50 cottages to be permitted in the other three quadrants of the city. Seattle is handling this program as if there would be huge demand for permits, but if the test run in the Southeast is any indication, there likely won’t be hundreds of applicants. But, then again, times are a-changing. In this economy, maybe Seattle residents are ready to wring every last dollar out of their property. Investing in a rental on your own lot is one way to do that.

    Here is an image of a cottage permitted by Seattle’s proposed program:

    ADU Seattle Sample.JPG

    Click here for a larger image.

    Seattle is also in the midst of reconsidering the “townhouse” which is a designation in the code that has been very controversial. Townhouses can now be built in clusters of 4 or 6. They have generally been resisted by single family neighborhoods because of the increase in density but also because they are seen as ugly.

    For those very reasons, the Congress of Residential Architects is leading a very intelligent campaign to rethink the code that governs the townhouse. Essentially, they argue, the townhouse designation fails because it puts many of the same requirements—parking and open space for example—that the code requires of single family homes on the denser, more compact townhouse designs. Allowing developers to design townhouses without parking or consolidating open space in to a courtyard in exchange for design review would allow flexibility to support more innovative designs and facilitate acceptance of townhouses by single family neighborhoods. In other words, they might look better and be more acceptable to neighbors.

    Here is an example of a townhome design using a courtyard to consolidate centralized open space. The project, called The Secret Garden, is in Seattle’s Capitol Hill neighborhood.

    ADU Secret Garden

    And speaking of courtyards, the City of Portland is working on amending its land use code to encourage more “courtyard housing” as an option for increased density in residential neighborhoods. Portland held a courtyard housing design competition that generated many ideas—with an emphasis on good design and courtyard housing that’s family friendly. The Portland City Council will be holding a hearing next month to consider a draft proposal to change to the code to allow construction of the types of projects that were winners in the competition. Projects like the Babylon Twelve (below) couldn’t be realized under the city’s existing code.

    ADU Portland Entry

    Finally, another group, the Central Puget Sound Chapter of the Northwest EcoBuilding Guild, is doing a series of presentations in Seattle to promote its walkable and livable communities. The Guild is working to promote more flexible use of single-family lots, including detached accessory dwelling units, and allowing corner stores in single family zones as well as flexible use of existing homes. One idea is to better use existing lots, especially corner lots, to create more housing opportunities.

    ADU Corner Lots
    Click here for larger image.

    What makes the Guild’s approach so refreshing is its emphasis on solutions that allow for more people in single family neighborhoods while preserving their character, something that is essential to these efforts.

    What these approaches all have in common is encouraging—and legalizing—more variety and options for property owners in single-family neighborhoods, while at the same time creating more density, affordability, and livability through better design. The moral of all the stories: density doesn’t have to go straight up. There are myriad options for density right in our own back yards.