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 Opelika (Lee County) – see this comment
Arizona Phoenix (called a ‘guesthouse’)
California Lake Elsinore – “second unit”
Los Angeles – defaults to state standards
San Diego (City)
– “Companion Unit”
San Diego (County)
San Francisco – Castro District
San Jose (Section 20.30.150)
Santa Cruz
Colorado Boulder
Connecticut  Norwalk
District of Columbia
Florida Jacksonville – not allowed
Idaho  Boise
Illinois Chicago – newly constructed ADUs not allowed, but older coach houses may be available for sale as units in a condo-like arrangement
Maryland Montgomery County
St. Mary’s County
Michigan Detroit – Not allowed except carriage houses built prior to 1940 (p. 461)
Traverse City
Missouri  Columbia
New Hampshire
New Jersey
New Mexico
New York New York City – Not allowed
North Carolina  Charlotte-Mecklenberg
North Dakota
Oregon Beaverton – section 40.05

Hillsboro – section 88a
Oregon City
Salem – Not allowed
Pennsylvania Philadelphia
Rhode Island
South Carolina
South Dakota
Tennessee  Nashville
Texas Austin
– only by special exceptionEl Paso
Port Aransas
San Antonio
Utah  Provo City — see this and this and this
Washington Olympia
West Virginia
Wisconsin Madison (p. 28-199)

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.

38 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 helpful. As you noted, we hope it assists planners to promote ADUs throughout the country.

      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:

  11. Ridge Turner
    November 19, 2014

    This is what I could fine for St Mary’s MD. Pulled from the ST. MARY’S COUNTY

    “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!!!

    • Martin John Brown
      November 29, 2014

      Grandfathering would be reasonable to me, but obviously you need to confirm with your particular local authorities to see how they interpret things. Good luck!

  13. Lee
    November 29, 2014

    Who do I contact for Sussex County in Delaware?

  14. D Jones
    November 29, 2014

    We are interested is this for the city of Elgin Illinois. We have a 115 year old home there. Anything you can find will be helpful.

  15. Martin John Brown
    November 29, 2014

    Hi Lee and D, your best bet will be to simply start calling around, for example the local planning or building permit office would be a good place to start. Let us know what you find out so we can post it here!

  16. Maxeem
    December 5, 2014

    Minneapolis, MN just passed ADU legislation to be allowed city-wide! :D

    • Martin John Brown
      December 5, 2014

      Maxeem, from my reading of the Minneapolis Star Tribune, at this date it is headed to the city council for a vote.

  17. Bryce
    December 6, 2014

    Hello, for the town of Norwalk, CT, here are the rules for an “Accessory Apartment:”

  18. Tom H.
    January 15, 2015

    Chicago has grandfathered in all existing ADUs (known locally and in the zoning code as “coach houses”), but does not allow new ADUs or expansions or major alterations to existing ADUs. Contrary to this site’s definition, in Chicago coach houses often are for-sale as stand alone condominiums as opposed to solely rentals on single-family properties.

  19. Jerry McIntire
    January 20, 2015

    Viroqua, WI doesn’t have any provision for ADUs in its zoning.

    • Martin John Brown
      January 21, 2015

      Hey Jerry, thanks for your comment. Can you clarify a bit about Viroqua? The long document you link to doesn’t seem to mention ADUs (I did a text search for “accessory dwelling”) but I’m not sure what this implies. ADUs aren’t mentioned and therefore… you can’t do them? or … you can do whatever you want? –Thanks!

      • Jerry McIntire
        March 3, 2015

        Martin, there is no provision for them so you can’t do them. If a lot is zoned for a duplex (many are) you can build a second residence. It must be at least 600 square feet.

  20. Burkley Allen
    January 22, 2015

    Nashville, TN passed an ordinance in 2014 allowing Detached Accessory Dwelling Units in residential areas zoned to allow duplexes.

    There was reluctance in areas that had downzoned to single family only to allow DADU’s as a blanket policy. Now some areas would like to come up with a “hybrid” zoning that would allow DADU’s but not full sized duplexes.
    Does any other city have a policy similar to that?

  21. carol
    February 24, 2015

    Regulations for Alameda County: Alameda and Castro Valley?

  22. Mona
    February 27, 2015

    We are up in Bellingham, WA. Our situation is a bit unique as we own a SFR, that we would like to convert to an ADU once we build a new house out in front of it. This is our place which we currently rent and she loves it: [link deleted for privacy’s sake — ed.]

    It was built with this idea in mind, to convert to an ADU, therefore was built to conform to ADU code. Within the city limits of Bellingham the ADU must be attached to the main residence. We had a designer help us with plans for the house and connection to the (hopefully) converted ADU. The code specifying the connection is very vague – really non-existent. It just says the structures need to be attached. The garage/ADU sits on the very back of the lot. Our design placement put the main house on the front of the lot as far forward as possible to allow a backyard between the ADU/main house. The connecting room would open onto the backyard, creating a courtyard feel. The City decided they did not like our connection design (too long), even though the code does not specify how it connects. They denied us. We withdrew our application as they said no way. Grrrr.

    The ADU Ordinance is now being revisited by the City Council and Planning Dept over the next few months, with the first meeting coming up next week. We will be active at those meetings, inform them of our situation and use your site for some of our references. It seems time the City entertain detached ADU’s as well. From everything I’m reading impact is negligible and outcome is positive. Our set up could not be more perfect for an ADU situation. I see why people give up trying to get approval, very frustrating!

    If you have any information or tips as we go through this process with the City, I’d appreciate it! We are hopeful things will turn in our favor so that we can resubmit converting this lovely place. We put everything on hold (have not started construction of the main house), hoping the tide will change and Bellingham will get more progressive with ADU development.

  23. Penelope
    March 3, 2015

    Does anyone happen to know the ADU laws for Sherwood, Oregon? I tried to find information online, but was unsuccessful. Thanks!

  24. Kirsten Sharer
    March 3, 2015

    Other Denver-Metro area, Colorado cities that allow ADUs-

    My husband and I (and my parents) are desperately waiting for Wheat Ridge to follow suite.

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