The Seattle Planning Commission report we discussed last week mentions a number of small and not-so-small ways to make Seattle more affordable for families by incentivizing the construction of more 2- and 3BR housing units. As the report notes, this will likely require controversial zoning changes in Seattle’s current single-family zones. Even if sweeping change is not on the horizon anytime soon, modest changes can be made to the code today that would increase affordability.
For example, in the last few years there have been efforts to allow more households in single-family zones via accessory dwelling units (ADUs). First came detached accessory dwelling unit (DADU), and later, the ADU (a basement or mother-in-law apartment). These were a good start, but they never quite took off in large numbers for a couple of reasons. It takes a fair amount of scratch to build a second house on your land, even if you’re willing to cut down trees or re-do landscaping to make it work. Most homeowners don’t have access to that kind of cash, and getting second mortgages has been a lot harder since the housing crash. Second, one unit must be owner-occupied, meaning that you can’t rent both units out.
One modest way to increase the stock of affordable housing would be simply to remove the owner-occupancy requirement on ADUs, making them more akin to a standard duplex. As commenter Eric writes in last week’s post, you could easily build a duplex inside the existing size envelope of a single-family house: built on no more than 35% of the property, obeying setback rules, etc. Such a duplex would easily “fit in” with the neighborhood. By removing the owner-occupancy requirement, it would be possible for an investor to build and operate a duplex as an investment property. That would open up a huge pile of potential capital and make ADUs more viable. If there were a way to sell them off separately as condos, all the better.
Keep in mind that I’m not talking about increasing the maximum allowable “house” size at all. The maximum size of a house on an SF-5000 lot depends on several factors, but can be as much as 5,000 square feet if built to three stories. A duplex of two, 2,000-square-foot units would fit within this envelope with room to spare. Furthermore, duplexes like this exist today in Seattle. There are a few, small, duplex zones, but some exist in single-family zones as well. They pre-date the current zoning laws and would be illegal to build today, but the earth still manages to spin despite their existence. Adding a few more wouldn’t solve everything, but it would give us some more options.