In November 2015 David Sucher proposed taking literally Seattle City Council member Juarez’s straw-man argument against alleviating the housing crisis by building “triplexes on every block”. He calculated that adding one triplex to every single-family block in Seattle would add 31,480 units to the housing supply, advancing the mayor’s HALA goal of adding 50,000 units city-wide while minimally impacting the character of any one neighborhood.
In contrast, Seattle’s existing zoning code allows development within a defined three-dimensional space. Since zones generally encompass at least one city block and demand for housing is extremely high, an increase in zoning capacity can lead to the rapid transformation of a neighborhood.
Mr. Sucher’s would be a novel approach. Alternately, the city could regulate building based on the total number of units for the block (or acre). If 20 units currently exist on the block and 30 are allowed, either ten single-family homes could add backyard cottages or become duplexes, or one house could be replaced by an 11 unit apartment building.
The advantage of this approach would be to allow capacity to be increased incrementally and systematically with the rise in population of the city or region. If the city population increased by 1%, every neighborhood in the city could be required to increase capacity by at least 1%. By making capacity increases automatic this approach could temper resistance to “upzoning”. Residents would generally not see large-scale replacement of the building stock of their neighborhood in a short period of time.