Accessory Dwelling Units Potential Zoning Options

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City Council Approves Standards for Detached Accessory Dwelling Units

On July 28, the Fairfax City Council approved a Zoning Ordinance to permit Detached Accessory Dwelling Units, subject to certain conditions (see below). This action by the City Council means that City property owners may now include either a detached or attached ADU as part of a single-family or duplex house.

The full standards for both attached and detached ADUs can be found in the Zoning Ordinance, under §3.5.5.D.1. A summary of those standards is below:

General Standards (for Attached and Detached ADUs):

  • One Per Lot: No more than one ADU per residential lot.
  • Size: The Gross Floor Area of an ADU may not exceed 35% of the house's Gross Floor Area.
  • Bedrooms: ADUs may not contain more than two bedrooms.
  • Parking Requirements: A lot containing an ADU must have at least 2 off-street driveway spaces.
  • Owner-Occupied: The property's owner must reside in either the house or the ADU.

Specific Standards for Attached ADUs:

  • Exterior Entrances: Any added external entrances to the ADU must be located on the side or rear of the house.

Specific Standards for Detached ADUs:

  • Location: A detached ADU can not be located between the house and the street, and if located in a house's side yard. it must be located towards the rear of the house.
  • Rear and Side Yard Setbacks: A detached ADU must be at least 20 feet from a rear lot line. If in the RH or RM zoning districts, a detached ADU must be at least 8 feet from a side (interior) lot line. If in the RL zoning district, a detached ADU must be at least 12 feet from any side (interior) lot line. This is detailed in §1.5.12 of the Zoning Ordinance.
  • Height: A Detached ADU structure may not exceed 20 feet, or the measured height of the house, whichever is less. The procedure for determining height measurements is detailed in §1.5.11 of the Zoning Ordinance.

For questions, please contact the Department of Community Development and Planning at 703- 385-7820.

City Council Approves Standards for Detached Accessory Dwelling Units

On July 28, the Fairfax City Council approved a Zoning Ordinance to permit Detached Accessory Dwelling Units, subject to certain conditions (see below). This action by the City Council means that City property owners may now include either a detached or attached ADU as part of a single-family or duplex house.

The full standards for both attached and detached ADUs can be found in the Zoning Ordinance, under §3.5.5.D.1. A summary of those standards is below:

General Standards (for Attached and Detached ADUs):

  • One Per Lot: No more than one ADU per residential lot.
  • Size: The Gross Floor Area of an ADU may not exceed 35% of the house's Gross Floor Area.
  • Bedrooms: ADUs may not contain more than two bedrooms.
  • Parking Requirements: A lot containing an ADU must have at least 2 off-street driveway spaces.
  • Owner-Occupied: The property's owner must reside in either the house or the ADU.

Specific Standards for Attached ADUs:

  • Exterior Entrances: Any added external entrances to the ADU must be located on the side or rear of the house.

Specific Standards for Detached ADUs:

  • Location: A detached ADU can not be located between the house and the street, and if located in a house's side yard. it must be located towards the rear of the house.
  • Rear and Side Yard Setbacks: A detached ADU must be at least 20 feet from a rear lot line. If in the RH or RM zoning districts, a detached ADU must be at least 8 feet from a side (interior) lot line. If in the RL zoning district, a detached ADU must be at least 12 feet from any side (interior) lot line. This is detailed in §1.5.12 of the Zoning Ordinance.
  • Height: A Detached ADU structure may not exceed 20 feet, or the measured height of the house, whichever is less. The procedure for determining height measurements is detailed in §1.5.11 of the Zoning Ordinance.

For questions, please contact the Department of Community Development and Planning at 703- 385-7820.

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  • Share Has there been any progress on this? Considering an adu on my property, but haven’t seen any sort of adaptions - wondering what setbacks will be changed in r-4 to allow us to accomplish this. Thanks on Facebook Share Has there been any progress on this? Considering an adu on my property, but haven’t seen any sort of adaptions - wondering what setbacks will be changed in r-4 to allow us to accomplish this. Thanks on X (formerly Twitter) Share Has there been any progress on this? Considering an adu on my property, but haven’t seen any sort of adaptions - wondering what setbacks will be changed in r-4 to allow us to accomplish this. Thanks on Linkedin Email Has there been any progress on this? Considering an adu on my property, but haven’t seen any sort of adaptions - wondering what setbacks will be changed in r-4 to allow us to accomplish this. Thanks link

    Has there been any progress on this? Considering an adu on my property, but haven’t seen any sort of adaptions - wondering what setbacks will be changed in r-4 to allow us to accomplish this. Thanks

    Tony asked 4 months ago

    The City of Fairfax is continuing to analyze potentially allowing detached Accessory Dwelling Units. The Planning Commission held a work session on this topic on April 13, and the City Council will discuss this at its May 12 meeting. Staff's presentation to the Planning Commission (which includes a summary of a draft Zoning amendment to allow Detached ADUs) is available here.

    If you are located in Fairfax County, rather than Fairfax City (the City does not have an R-4 Zoning District), please consult the following page for updates on Fairfax County's potential actions on this topic: https://www.fairfaxcounty.gov/planning-development/zoning-ordinance/amendments/accessory-living-units

  • Share What are the zoning regulations to convert a single family home into a duplex in Fairfax county 22309 zip code? on Facebook Share What are the zoning regulations to convert a single family home into a duplex in Fairfax county 22309 zip code? on X (formerly Twitter) Share What are the zoning regulations to convert a single family home into a duplex in Fairfax county 22309 zip code? on Linkedin Email What are the zoning regulations to convert a single family home into a duplex in Fairfax county 22309 zip code? link

    What are the zoning regulations to convert a single family home into a duplex in Fairfax county 22309 zip code?

    Regina Sanchez asked about 1 year ago

    This is the City of Fairfax, so these regulations do not apply to your property. You will need to contact Fairfax County Land Development at LandDevelopmentServices@fairfaxcounty.gov or 703-222-0801.

    The link to their website can be found here.

  • Share Good morning, As you mentioned in our previous correspondence two months ago, staff was planning to recommend amendments to the Zoning Ordinance to remove the current occupancy limitations on Accessory Dwelling Units (i.e., requiring the resident to be either disabled or age 55+). You anticipated bringing those amendments forward to City Council this spring or early summer. Has that process moved forward yet? If not, is there a specific date scheduled for the meeting? Will the general public be allowed to attend or participate in that discussion? Additionally, will the possibility of allowing detached ADUs be addressed as part of this process? If so, is there a projected timeline for when that discussion or proposal might take place? Thank you for your time and any updates you can provide. on Facebook Share Good morning, As you mentioned in our previous correspondence two months ago, staff was planning to recommend amendments to the Zoning Ordinance to remove the current occupancy limitations on Accessory Dwelling Units (i.e., requiring the resident to be either disabled or age 55+). You anticipated bringing those amendments forward to City Council this spring or early summer. Has that process moved forward yet? If not, is there a specific date scheduled for the meeting? Will the general public be allowed to attend or participate in that discussion? Additionally, will the possibility of allowing detached ADUs be addressed as part of this process? If so, is there a projected timeline for when that discussion or proposal might take place? Thank you for your time and any updates you can provide. on X (formerly Twitter) Share Good morning, As you mentioned in our previous correspondence two months ago, staff was planning to recommend amendments to the Zoning Ordinance to remove the current occupancy limitations on Accessory Dwelling Units (i.e., requiring the resident to be either disabled or age 55+). You anticipated bringing those amendments forward to City Council this spring or early summer. Has that process moved forward yet? If not, is there a specific date scheduled for the meeting? Will the general public be allowed to attend or participate in that discussion? Additionally, will the possibility of allowing detached ADUs be addressed as part of this process? If so, is there a projected timeline for when that discussion or proposal might take place? Thank you for your time and any updates you can provide. on Linkedin Email Good morning, As you mentioned in our previous correspondence two months ago, staff was planning to recommend amendments to the Zoning Ordinance to remove the current occupancy limitations on Accessory Dwelling Units (i.e., requiring the resident to be either disabled or age 55+). You anticipated bringing those amendments forward to City Council this spring or early summer. Has that process moved forward yet? If not, is there a specific date scheduled for the meeting? Will the general public be allowed to attend or participate in that discussion? Additionally, will the possibility of allowing detached ADUs be addressed as part of this process? If so, is there a projected timeline for when that discussion or proposal might take place? Thank you for your time and any updates you can provide. link

    Good morning, As you mentioned in our previous correspondence two months ago, staff was planning to recommend amendments to the Zoning Ordinance to remove the current occupancy limitations on Accessory Dwelling Units (i.e., requiring the resident to be either disabled or age 55+). You anticipated bringing those amendments forward to City Council this spring or early summer. Has that process moved forward yet? If not, is there a specific date scheduled for the meeting? Will the general public be allowed to attend or participate in that discussion? Additionally, will the possibility of allowing detached ADUs be addressed as part of this process? If so, is there a projected timeline for when that discussion or proposal might take place? Thank you for your time and any updates you can provide.

    Sasha asked about 1 year ago

    Staff held a work session with the Planning Commission on May 12 to discuss several proposed text amendments, including the removal of the age and disability requirements for ADUs. A similar work session with City Council is scheduled for June 3. Public hearings for both Planning Commission and City Council are anticipated for later this year.

    While public comment is not taken during work sessions, you are welcome to speak during the general public comment period at any Planning Commission or City Council meeting and during the public hearings on this item. You may also submit written comments via email to the Planning Commission and/or City Council.

    Detached ADUs are not a part of this text amendment package but the project to analyze the possibility of allowing detached ADUs is ongoing and there will be a substantial public engagement effort as a part of that analysis. Updates will be provided as that project progresses.

  • Share is ALU required to be connect to the local fire department? on Facebook Share is ALU required to be connect to the local fire department? on X (formerly Twitter) Share is ALU required to be connect to the local fire department? on Linkedin Email is ALU required to be connect to the local fire department? link

    is ALU required to be connect to the local fire department?

    Durrabkhan asked over 1 year ago

    For attached Accessory Dwelling Units (ADUs), there are fire suppression standards in the building code. For more detailed information, you can contact Code Administration at CodeAdministration@fairfaxva.gov or call 703-385-7830. Since the City currently does not allow for detached ADUs, there are no standards for connection to the fire department. As the possibility of allowing detached ADUs is explored, access and capacity of emergency services will be assessed.

  • Share Where does this policy change stand? There was a meeting scheduled to take place Nov of last year, but I see no follow-up on that. The link to the Comprehensive Plan is dead (Page not found). Is there a new link? Is there more information? Has a decision been made on the policy change? on Facebook Share Where does this policy change stand? There was a meeting scheduled to take place Nov of last year, but I see no follow-up on that. The link to the Comprehensive Plan is dead (Page not found). Is there a new link? Is there more information? Has a decision been made on the policy change? on X (formerly Twitter) Share Where does this policy change stand? There was a meeting scheduled to take place Nov of last year, but I see no follow-up on that. The link to the Comprehensive Plan is dead (Page not found). Is there a new link? Is there more information? Has a decision been made on the policy change? on Linkedin Email Where does this policy change stand? There was a meeting scheduled to take place Nov of last year, but I see no follow-up on that. The link to the Comprehensive Plan is dead (Page not found). Is there a new link? Is there more information? Has a decision been made on the policy change? link

    Where does this policy change stand? There was a meeting scheduled to take place Nov of last year, but I see no follow-up on that. The link to the Comprehensive Plan is dead (Page not found). Is there a new link? Is there more information? Has a decision been made on the policy change?

    MJS asked over 1 year ago

    Staff is planning to recommend amending the Zoning Ordinance to remove the existing limitations on ADU occupancy (requiring either a disabled resident, or a resident age 55+).  We anticipate bringing those amendments forward to City Council this spring or early summer.  Considerations for potentially permitting detached accessory dwelling units are still being analyzed; updates will be posted on this Engage page when available.  Staff will hold another community meeting to discuss any potential options for detached ADUs.


    The link to the Comprehensive Plan has been fixed and can also be found here: City of Fairfax 2035 Comprehensive Plan

  • Share Good morning. Can i build a 20x24 addition/ADU attached to the back of my house for my elderly parents to live in? How long is the permit process? Beside engineering plans anything else I need to do? on Facebook Share Good morning. Can i build a 20x24 addition/ADU attached to the back of my house for my elderly parents to live in? How long is the permit process? Beside engineering plans anything else I need to do? on X (formerly Twitter) Share Good morning. Can i build a 20x24 addition/ADU attached to the back of my house for my elderly parents to live in? How long is the permit process? Beside engineering plans anything else I need to do? on Linkedin Email Good morning. Can i build a 20x24 addition/ADU attached to the back of my house for my elderly parents to live in? How long is the permit process? Beside engineering plans anything else I need to do? link

    Good morning. Can i build a 20x24 addition/ADU attached to the back of my house for my elderly parents to live in? How long is the permit process? Beside engineering plans anything else I need to do?

    Randygalliani asked over 1 year ago

    Thank you for your question. You will need to submit an application through the permit portal (link here). Please refer to the zoning webpage for additional information and if you have questions, you can email zoning@fairfaxva.gov or call 703-385-7820.

  • Share How do you take into account the negative impact on a neighbor's house who may be a very short distance from the ADU and be basically in the back yard of your house? It will also affect the value of your house having an ADU so close and the noise that will also affect the quality of your life. Fairfax, from what I read, has a minimum requirement of 2 acres which would address these concerns. on Facebook Share How do you take into account the negative impact on a neighbor's house who may be a very short distance from the ADU and be basically in the back yard of your house? It will also affect the value of your house having an ADU so close and the noise that will also affect the quality of your life. Fairfax, from what I read, has a minimum requirement of 2 acres which would address these concerns. on X (formerly Twitter) Share How do you take into account the negative impact on a neighbor's house who may be a very short distance from the ADU and be basically in the back yard of your house? It will also affect the value of your house having an ADU so close and the noise that will also affect the quality of your life. Fairfax, from what I read, has a minimum requirement of 2 acres which would address these concerns. on Linkedin Email How do you take into account the negative impact on a neighbor's house who may be a very short distance from the ADU and be basically in the back yard of your house? It will also affect the value of your house having an ADU so close and the noise that will also affect the quality of your life. Fairfax, from what I read, has a minimum requirement of 2 acres which would address these concerns. link

    How do you take into account the negative impact on a neighbor's house who may be a very short distance from the ADU and be basically in the back yard of your house? It will also affect the value of your house having an ADU so close and the noise that will also affect the quality of your life. Fairfax, from what I read, has a minimum requirement of 2 acres which would address these concerns.

    mowry1000 asked over 1 year ago

    Fairfax City's Comprehensive Plan notes that if zoning standards are revised for Accessory Dwelling Units, that those standards should ensure that they "do no negatively impact surrounding neighborhoods." This could mean setting standards for a minimum distance from a property line, or required screening of ADU units, etc. - all these standards will be considered. There will be additional community meetings and public sessions on this topic so be sure to subscribe to this page for updates. Should you have specific concerns, feel free to reach out to staff or to City Councilmembers to ensure that those concerns may be understood.

  • Share Not a question, just a comment. I'd love to be able to build a standalone ADU on my city property. It's not that easy to incorporate an ADU into a split-level like mine because the ceilings are low and the floor plans do not lend themselves well to being subdivided. Retirees such as myself are property-rich but cashflow-poor, and being able to rent out an external ADU would be very helpful to everyone. I plan on staying in my home instead of relocating to a nursing facility in the future, and it would be ideal to be able to offer living space in an ADU as partial payment to a live-in caretaker. on Facebook Share Not a question, just a comment. I'd love to be able to build a standalone ADU on my city property. It's not that easy to incorporate an ADU into a split-level like mine because the ceilings are low and the floor plans do not lend themselves well to being subdivided. Retirees such as myself are property-rich but cashflow-poor, and being able to rent out an external ADU would be very helpful to everyone. I plan on staying in my home instead of relocating to a nursing facility in the future, and it would be ideal to be able to offer living space in an ADU as partial payment to a live-in caretaker. on X (formerly Twitter) Share Not a question, just a comment. I'd love to be able to build a standalone ADU on my city property. It's not that easy to incorporate an ADU into a split-level like mine because the ceilings are low and the floor plans do not lend themselves well to being subdivided. Retirees such as myself are property-rich but cashflow-poor, and being able to rent out an external ADU would be very helpful to everyone. I plan on staying in my home instead of relocating to a nursing facility in the future, and it would be ideal to be able to offer living space in an ADU as partial payment to a live-in caretaker. on Linkedin Email Not a question, just a comment. I'd love to be able to build a standalone ADU on my city property. It's not that easy to incorporate an ADU into a split-level like mine because the ceilings are low and the floor plans do not lend themselves well to being subdivided. Retirees such as myself are property-rich but cashflow-poor, and being able to rent out an external ADU would be very helpful to everyone. I plan on staying in my home instead of relocating to a nursing facility in the future, and it would be ideal to be able to offer living space in an ADU as partial payment to a live-in caretaker. link

    Not a question, just a comment. I'd love to be able to build a standalone ADU on my city property. It's not that easy to incorporate an ADU into a split-level like mine because the ceilings are low and the floor plans do not lend themselves well to being subdivided. Retirees such as myself are property-rich but cashflow-poor, and being able to rent out an external ADU would be very helpful to everyone. I plan on staying in my home instead of relocating to a nursing facility in the future, and it would be ideal to be able to offer living space in an ADU as partial payment to a live-in caretaker.

    Dave Marney asked over 1 year ago

    Thank you for your comment!

  • Share What are we doing to balance the additional people ADUs will bring with infrastructure requirements? More people will need more services like police, fire, water, sewer, transportation, etc. on Facebook Share What are we doing to balance the additional people ADUs will bring with infrastructure requirements? More people will need more services like police, fire, water, sewer, transportation, etc. on X (formerly Twitter) Share What are we doing to balance the additional people ADUs will bring with infrastructure requirements? More people will need more services like police, fire, water, sewer, transportation, etc. on Linkedin Email What are we doing to balance the additional people ADUs will bring with infrastructure requirements? More people will need more services like police, fire, water, sewer, transportation, etc. link

    What are we doing to balance the additional people ADUs will bring with infrastructure requirements? More people will need more services like police, fire, water, sewer, transportation, etc.

    Redacted 2 asked over 1 year ago

    Accessory dwelling units are not anticipated to develop at such a density that would heavily impact infrastructure. For major developments, City agencies review development proposals to assess potential impacts to infrastructure and seek mitigation measures from developers. While the City is not currently able to require mitigation for services, a fiscal impact study is completed for each development proposal to estimate whether cost burdens for services from the new development would exceed additional revenues.

  • Share What precisely is being proposed here? This is very vague and includes no details of what changes are being considered. While it addresses current ADU allowances, it does not address what is proposed, e.g. detached (separate structure) ADU dwellings; currently not permitted. If detached ADUs is what this is addressing, specifics such as property line set-backs, sewer, utility, etc need to be detailed. Also, if a detached ADU is what is being proposed, how does this fit into zoning and how would it be handled when sale of property occurs, e.g. would age requirements remain in place? on Facebook Share What precisely is being proposed here? This is very vague and includes no details of what changes are being considered. While it addresses current ADU allowances, it does not address what is proposed, e.g. detached (separate structure) ADU dwellings; currently not permitted. If detached ADUs is what this is addressing, specifics such as property line set-backs, sewer, utility, etc need to be detailed. Also, if a detached ADU is what is being proposed, how does this fit into zoning and how would it be handled when sale of property occurs, e.g. would age requirements remain in place? on X (formerly Twitter) Share What precisely is being proposed here? This is very vague and includes no details of what changes are being considered. While it addresses current ADU allowances, it does not address what is proposed, e.g. detached (separate structure) ADU dwellings; currently not permitted. If detached ADUs is what this is addressing, specifics such as property line set-backs, sewer, utility, etc need to be detailed. Also, if a detached ADU is what is being proposed, how does this fit into zoning and how would it be handled when sale of property occurs, e.g. would age requirements remain in place? on Linkedin Email What precisely is being proposed here? This is very vague and includes no details of what changes are being considered. While it addresses current ADU allowances, it does not address what is proposed, e.g. detached (separate structure) ADU dwellings; currently not permitted. If detached ADUs is what this is addressing, specifics such as property line set-backs, sewer, utility, etc need to be detailed. Also, if a detached ADU is what is being proposed, how does this fit into zoning and how would it be handled when sale of property occurs, e.g. would age requirements remain in place? link

    What precisely is being proposed here? This is very vague and includes no details of what changes are being considered. While it addresses current ADU allowances, it does not address what is proposed, e.g. detached (separate structure) ADU dwellings; currently not permitted. If detached ADUs is what this is addressing, specifics such as property line set-backs, sewer, utility, etc need to be detailed. Also, if a detached ADU is what is being proposed, how does this fit into zoning and how would it be handled when sale of property occurs, e.g. would age requirements remain in place?

    DACOX45 asked almost 2 years ago

    Thank you for your question regarding the ADU Community Meeting.

    There is not a specific policy being proposed right now – the meeting is in response to direction that City Council provided staff after a July work session that focused on Accessory Dwelling Units.  At that meeting, Council asked staff to:

    1. Eliminate the existing requirement that ADU occupants be aged 55+, or have a disability; and
    2. Investigate whether allowing Detached Accessory Dwelling Units would be beneficial to the City.


    This second item will be the Community Meeting’s major discussion point.  The meeting’s purpose is to gauge community sentiments regarding many of the issues you mentioned.  We plan to discuss Detached ADUs in general, and also potential options for ADU standards such as setbacks, size limitations, parking, etc. – similar items to what you mention in your question.  There’s little detail right now because we would like to solicit community feedback before reporting back to City Council and Planning Commission.

    I hope you’re able to attend the community meeting – should you have any further questions, please let us know.

Page last updated: 29 Jul 2026, 05:47 AM