I recently did a collaboration with the Sightline Institute to study where there are multi-unit residences in single-family zones. These places are the remnants of the time before Seattle (and many other cities) went through processes of downzoning. These downzones, often along with redlining, created huge areas that have restricted the building of housing, and become, especially in recent years, areas of exclusivity and unaffordability. Working people and the middle class can no longer afford to buy even the most modest houses in these exclusively zoned neighborhoods.
Because of exclusive single-family zoning, we have missed out on generations of development of naturally affordable housing, as new construction ages over the years and becomes affordable. Very little multiplex housing has been built in these neighborhoods since the 60’s, so the opportunities for more affordable aged multi-unit housing have not been realized. If Seattle had continued to allow the development of duplexes, triplexes, and quad-plexes in these neighborhoods, instead of downzoning over half of its area, we would not be facing the affordability crisis that we currently face.
See the full, expanded map.
Margaret Morales’ article, which accompanies the map, can be read at the Sightline Institute.