1.4 Million ADUs: Some Interesting Stats About Granny Flats

  • July 29th 2020

by Nena Perry-Brown

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A recent report from Freddie Mac takes stock of accessory dwelling units (ADUs) around the country and offers evidence of the growing popularity of the property type. 

The data shows that there are 1.4 million single-family homes with ADUs nationwide, and the number of ADUs grew by an average of 8.6% year-over-year between 2009 and 2019. Between 2000 and 2019, the share of active listings with ADUs grew from 1.6% to 6.8%, and the number of homes sold with ADUs grew from 1% to 4.2%.

Growth in number of ADUs nationwide. Click to enlarge.

Similarly, ADUs grew as part of the rental market: between 2003 and 2019, the share of ADU rental listings grew from 1.8% to 4.1%. It should also be noted, however, that despite legal and zoning changes in DC and other jurisdictions in the area, barriers remain to the construction of detached ADUs. For DC in particular, fewer than 50 ADUs have been permitted annually since the 2016 zoning rewrite.

Mapping prevalence of attached or detached ADUs. Click to enlarge.

It is unsurprising then that no state in the DC area appears in the top ten for ADU supply, nor is the DC area in the top 25 of metro areas in fastest growth of ADU supply from 2015 to 2018. 

The study does not account for owners whose ADUs are not advertised, are advertised without using "key-phrases", or whose home sales took place outside of the MLS. There are also instances where pre-existing ADUs may be counted as new if those units were not previously marketed.

The study uses over 20 years of data from 600 million MLS transactions nationwide to note when new ADUs hit the market; unpermitted "shadow" ADUs are not included.

Thumbnail photo is an ADU by Ileana Schinder

See other articles related to: accessory dwelling units, accessory dwellings, freddie mac

This article originally published at https://dc.urbanturf.com/articles/blog/14-million-adus-some-interesting-stats-about-granny-flats/17120.

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