The City of Seattle has released their 2022 annual report of ADUs

Key takeaways

Most importantly, there has been a big increase in the number of ADU and DADU permits issued. In 2022 there were 551 DADUs permitted which is approximately four times the number permitted five years ago. While not all of these will get built, it is a lot of DADUs, and they are fairly evenly spread out through the city.

The effects of the building code changes to facilitate ADU construction?

It appears that the removal of the owner occupancy requirements and the addition of allowance of 2 ADUs on a property were the most impactful code changes. A full 40% of ADUs permitted were projects where 2 new ADUs were being planned. An estimated 34% of ADU projects were the result of the removal of an existing single family residence (SFR) and the construction of a new SFR plus one or more ADUs. These projects represent a new housing typology for Seattle. A typology that we look forward to shaping in a positive way.

Another big impact of the land-use code changes of 2019 is the addition of a floor area limit (FAR) to the size of new SFRs. Largely because ADUs are excluded from FAR calculations, 70% of new SFRs permitted in 2022 included an ADU.

For full details read the report

ADU Report