Strategy-of-the-Month: Accessory Dwelling Units
Posted Date: February 10, 2009


Regulatory Barriers Clearinghouse
Strategy-of-the-Month Club
February 2009
Built-out communities burdened with high housing costs
are increasingly turning to Accessory Dwelling Units
(ADUs) as an effective and inexpensive way to expand
affordable housing options. Accessory dwelling units -
also referred to as granny flats, accessory apartments,
or second units - are additional living quarters
equipped with kitchen and bathroom facilities that are
independent of the primary dwelling unit on single-
family lots. A publication prepared for the U.S.
Department of Housing and Urban Development, Accessory
Dwelling Units: Case Study, examines the history and
benefits of ADUs, and highlights six communities that
have successfully implemented ADU ordinances.
The report identifies ADUs as an affordable housing
option for many low- and moderate-income residents.
Additionally, second units are less costly to develop
than new single-family homes on separate lots, and also
facilitate an efficient use of the existing housing
stock and infrastructure. With detailed descriptions of
ADU ordinances and programs adopted by six case study
areas, the report explores various methods of revising
existing regulations to encourage ADU development. Each
of the study areas adopted variations of bylaws and code
revisions that allow ADUs to be built by right or by
special permit. Revising restrictive zoning policies and
adopting incentive programs to encourage ADU development
has proven advantageous to the study areas. The report
concludes that successful ADU programs must be flexible,
uncomplicated, include fiscal incentives, and be
supported by public education campaigns so as to
engender and maintain community support.
To view the report in its entirety, please visit You
can also order a hard copy of the report by calling HUD
USER at 1-800-245-2691, option 1.
We hope this information proves useful to you in your
efforts to grow your region's affordable housing stock.
If you have regulatory reform strategies or resources
that you'd like to share, email us at, call us at 1-800-245-2691 (option
4), or visit our website at
Feel free to forward this message to anyone who is
working to reduce regulatory barriers to affordable
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