Accessory Dwellings

A one-stop source about accessory dwelling units, multigenerational homes, laneway houses, ADUs, granny flats, in-law units…

What are the rules where I live?

Rules for creating ADUs vary from place to place.  Check the table below for links to your area.

Please remember this is a volunteer-driven site!  If you don’t see your city, or the link for your city is wrong, please let us know with a comment below — or even better, do some digging and leave the correct info in your comment.  With your help, we can build an up-to-date list for the entire continent.

State/Province City/County
Alabama
Alaska
Arizona Phoenix (called a ‘guesthouse’)
Arkansas
California Lake Elsinore – “second unit”
Los Angeles – defaults to state standards
Sacramento
San Diego (City)
– “Companion Unit”
San Diego (County)
San Francisco – Castro District
San Jose (Section 20.30.150)
Santa Cruz
Colorado Boulder
Connecticut
Delaware
District of Columbia
Florida Jacksonville – not allowed
Georgia
Hawaii
Idaho
Illinois Chicago – not allowed
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland Montgomery County
St. Mary’s County
Massachusetts
Michigan Detroit – Not allowed except carriage houses built prior to 1940 (p. 461)
Traverse City
Minnesota
Mississippi
Missouri  Columbia
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York New York City – Not allowed
North Carolina  Charlotte-Mecklenberg
North Dakota
Ohio
Oklahoma
Oregon Beaverton – section 40.05
Bend

Corvallis
Eugene
Gresham
Hillsboro – section 88a
Medford
Oregon City
Portland
Salem – Not allowed
Springfield
Pennsylvania Philadelphia
Pittsburg
Rhode Island
South Carolina
South Dakota
Tennessee
Texas Austin
Dallas
– only by special exceptionEl Paso
Houston
San Antonio
Utah  Provo City — see this and this and this
Vermont
Virginia
Washington Olympia
Seattle
West Virginia
Wisconsin Madison (p. 28-199)
Wyoming

More details about Oregon cities

If the table above isn’t enough info for you, here is an older table that focuses on Oregon cities, and has some more details about specific regulations:  Accessory Dwelling Unit Zoning Codes .ADU Zoning Matrix

If you’re willing to add to this dataset for your state, please contact us.

Even more details about Portland, Oregon

For more in depth information on Portland’s ADU regulations, review the following information.An introduction to the rules governing ADUs in Portland, OR is contained in this on-line guide. Among its more helpful links are:

Portland also allows accessory structures, some permitted and some not, that don’t qualify as separate dwelling units yet often have attributes similar to ADUs. For a table-format summary of codes related to these other structures, check out this Accessory Structure (Informal) Code Guide.

18 comments on “What are the rules where I live?

  1. Chris Neubecker
    May 9, 2014

    Thank you for sharing this information. This is wonderful research and will help planners in other communities trying to promote ADUs to advance this cause in our own jurisdictions.

    • linamenard
      May 9, 2014

      Dear Chris,

      We’re so glad you’ve found the information on AccessoryDwellings.org helpful. As you noted, we hope it assists planners to promote ADUs throughout the country.

      Sincerely,
      Lina Menard
      A fellow planner and coordinator of the ADU Case Studies Project

  2. J. Schmidt
    May 9, 2014

    Anything known about Long Island/Suffolk County/Brookhaven Town?

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  5. Lora Shaner
    September 5, 2014

    How about Nevada – particularly Las Vegas?

  6. Sharri Chaidez
    September 9, 2014

    I live in Sacramento, California. I have been contemplating adding a 4/plex to my current property, but I’m not sure of the codes or regulations regarding this type of addition. My residence is also considered a historical property. Where would I begin to find information about adding an adu?

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  8. captainlucianchiroptera
    September 15, 2014

    I’m curious if there has been any word if Salem, OR will be changing it’s laws any time soon, or if I should start looking for places around Salem, while I maintain my current place of employment…

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  10. Dylan
    October 2, 2014

    Columbia, Missouri now allows Accessory Dwelling Units in all R-2 zoned residential lots, excluding two neighborhoods / overlay districts. While the majority of residential lots in the city are zoned R-1 and are not affected by the new ADU ordinance, it is possible for future ordinances to extend this to the R-1 residential lots as well.
    The relevant information can be found on the City of Columbia’s website: http://www.gocolumbiamo.com/community_development/planning/AccessoryDwellingUnits.php

  11. Ridge Turner
    November 19, 2014

    This is what I could fine for St Mary’s MD. Pulled from the ST. MARY’S COUNTY
    DEPARTMENT OF LAND USE AND GROWTH MANAGEMENT FAQ site.

    http://www.stmarysmd.com/docs/PermitsFAQ.pdf

    “May I build a second home/accessory apartment on
    my property?

    An alternative to a second home is an accessory dwelling unit. An accessory dwelling unit may be part of the principal dwelling or in a detached accessory structure (CZO Section 51.3.105.a.1). If part of the principal dwelling, it must be at least 300 square feet but may not exceed 30 % of the gross floor area. If in an accessory structure, the dwelling unit may contain no more than 2 bedrooms and may not exceed 50% of the gross floor area of the accessory structure (CZO Section 51.3.105.a.2).
    Accessory dwelling units are permitted in all zoning districts except in the CC, I and OBP districts (CZO Schedule 50.4.105).
    Accessory dwelling units are not subject to density limitations except in the RCA Critical Area overlay where they are considered a principal dwelling unit (reference to be provided). Thus, properties outside the RCA Critical Area are permitted “by right” to an accessory dwelling unit provided a building permit is obtained. There may be only one accessory dwelling unit per lot or parcel (CZO Section 51.3.105.a.3).
    Related Issues
    Contact the Health Department at 301-475-4321 for well and septic system requirements.

  12. Lynn Poindexter
    November 21, 2014

    Question: If an ADU existed before a property was annexed into a city, is it typical for that ADU to be considered ‘grandfathered against such city’s rules? Any insight greatly appreciated!!!

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