Eli Spevak who was a co-presenter with me several weeks ago on a panel exploring alternative housing models sent me a great blog post outlining a model code for what we call in Seattle DADUs or Detached Accessory Dwelling Units. This housing option has also been called backyard cottages.

As editors of www.accessorydwellings.org, we’d like to offer a model zoning code that ensures ADUs are small and discreet, while also providing enough latitude in their creation that they actually get built. Commentary is provided in italics, along with some alternative clauses that could be helpful for particular circumstances. You can also download it as an editable Word or PDF file. This needn’t be a static document. I expect we will update it periodically as we gain more experience with ADUs and the codes that govern them.

The sample code addresses one of the most troublesome aspects of DADUs in Seattle, the owner occupancy requirements. This makes DADUs a mostly ineffective tool to increase housing supply.

Owner-occupancy requirements make properties with ADUs unsuitable for income-based valuation by appraisers, constraining their value and making them more difficult to finance. Affordable housing restrictions on ADUs sound appealing, except that deed restrictions and tenant income screenings are (unsurprisingly) obstacles for mom-and-pop landlords (fortunately, ADUs provide a surprising amount of market-based affordable housing without subsidy or use restriction).

Allowing homeowners to build and rent out their DADU  (or sell them) is essential for improving the financing of the units. Without that, most people would have to add more debt to their own home without a way to recover that investment. The model code is a good place for Seattle to start creating options for using DADUs to increase housing supply.