Questions and Answers about Accessory Dwelling Units

Accessory Dwelling Units:What Are They and Other Frequently Asked Questions


The Board is currently considering a local law that will allow homes in Single Family Residential Zoning Districts the ability to add an additional dwelling unit on the property of an existing home. Accessory Dwelling Units have also been called a mother-in-law apartment, granny flat or an in-law suite. The legislation is designed to be a low impact approach to increasing the number of affordable housing units in the Village while also providing a way for seniors in our community to age in place. As has been said by the Westchester County Planning Department, and housing experts with the Village’s Housing Affordability Task Force, this is just one tool in the toolbox to address the affordable housing problem in our region.

Please see below answers to general questions about Accessory Dwelling Units as well as specific questions the Village has received from residents.

What is an Accessory Dwelling Unit? (ADU)

An ADU is a 2nd dwelling unit on the property of an existing home in a Single Family Residential Zone. It can be attached (basement, attic, addition) or detached (garage, cottage). In the proposed legislation, ADUs must include a kitchen and a bathroom, and must adhere to all building code regulations in terms of safety. No more than one ADU is permitted per lot.

Are owners required to live on the property?

Yes. The proposed legislation requires the owner to live on the property in either unit.

Where are ADUs permitted?

In Single Family Residential Zones. Newly constructed detached ADUs are only permitted in zones where the minimum lot size is 15,000 square feet or greater (R-15 through R-80).

Is the proposed ADU legislation going to change all Single-Family Residential Zones to Multi-family zoning districts?

No. The Village Code has separate zoning districts where multi-family units are allowed. The Accessory Dwelling Unit proposal would only allow one additional accessory dwelling unit that complies with the law per lot, and that unit would be confined to the existing single-family structure, or in the larger lot Zones R-15 and above, there could be a new detached accessory structure that conforms to the size and setback restrictions of the law.   

Was this legislation considered in the Tarrytown Comprehensive Plan?

Yes. The Tarrytown Comprehensive Plan was developed over the course of many months with widespread community input. Chapter 10 of the section on Planning Goals and Policies emphasizes the need to “ensure housing stock supports a diverse and multi-generational community,” and implementation action 10.b.ii states: “Amend single-family zoning to permit accessory, establish guidelines and permitting process.” The Housing Affordability Task Force was charged with considering this goal and implementation action from the Comprehensive Plan and spent more than a year researching and crafting this proposed legislation with the Village Attorney and the Village Administrator for the Board to consider.   

How big can an ADU be?

In the proposed legislation ADUs must be a minimum of 300 sq ft and can be a maximum of 1,000 sq ft, but must not be greater than 50% of the size of the existing property. ADUs can have no more than 2 bedrooms, except in the zones with smaller lots (R-5, R-7.5 and R-10) where only studios or one-bedrooms are permitted.

How many people can live in an ADU? Is there a limit?

ADUs can be no more than two bedrooms and no more than 1,000 sf. The New York State Building Codes limit the number of people who can inhabit a residence based on square footage.

Is additional parking required?

Yes. One off-street parking space is required for an ADU, in addition to the two off-street parking spaces required for all single family residences. The only exception is for dwellings north of Rt. 119 and west of Broadway where no additional parking will be required for an ADU.

Is Land Use Board Review required?

If an ADU is constructed within the existing footprint of an existing structure, no site plan review is required unless the property is in the historic district or is a historic landmark. However, adherence to building code standards for safety, fire codes, egress, etc, is ALWAYS required. If the ADU expands the existing footprint or square footage of the existing structure, then land use board review is required if the increase meets the Code’s existing thresholds for any improvement (ADU or otherwise).

Is my neighborhood going to be transformed by this legislation?

Based on the experiences of other communities, no. The purpose of the legislation is to offer a low-density and low-impact opportunity to chip away at the housing crisis in our area. It also is the rare tool that offers benefits to existing residents (in terms of additional income) and new residents (in terms of a new unit). The following is data from other Westchester Villages with Accessory Dwelling Unit provisions, the years they were enacted, and the number of units in each community to date (source: Westchester County Planning Department):

  • Briarcliff Manor (2014): 26
  • Buchanan (1989): 25
  • Croton on Hudson (2015): 10
  • Hastings on Hudson (1997): 23
  • Irvington (2016): 2
  • Pleasantville (2020): 5

Anecdotally, Hastings on Hudson has had Accessory Dwelling legislation in place since the 1980s. Building Inspector Charles Minozzi, Jr. reports that in the 12 years he has been inspecting units and handling application renewals, he has experienced a single complaint from a neighbor regarding a unit and does not perceive a change to neighborhoods as a result of the units in place. In addition, Hastings recently relaxed restrictions to the creation of ADUs given how favorably they have been received.

If this legislation is so low impact, why should we institute it at all? Don’t we have enough affordable housing in the Village?

The purpose of ADU legislation is to provide an opportunity for those who need it, whether it be to house a family member who needs to move back home, or receive rental income from a second unit in order to age in place. According to the 2019 Housing Needs Assessment for the County, and specifically the Municipal Housing Snapshot for Tarrytown, almost 20% or 1 in 5 renters and more than 13% of owners (more than 1 in 10) in Tarrytown are severely cost burdened, which means they pay more than 50% of their annual income on housing. This legislation offers one alternative for those who need it.

Who will enforce the 6-month minimum lease and how will you monitor compliance this and other aspects of the legislation such as the requirement that the homeowner live in one of the units?

Every ADU will require a building permit. Prior to issuance of a Certificate of Occupancy, the homeowner will also have to register the Accessory Dwelling Unit  and attest to understanding and compliance with ADU regulations. The owner's affidavit will need to be signed every time there is a transfer of ownership for properties with an ADU. As with many other building and zoning code issues, the Building Department has a range of tools at its disposal, including resident complaints, to monitor compliance with building and zoning requirements.

What happens to the tenant should the property owner(s) die and the property is transferred or sold to a non-resident? How will the village enforce the owner occupant requirement? 

The property owner will have the same responsibilities as any landlord, and the terms of a lease when the property changes hands will apply.

In terms of the Building Department’s ability to track principle ownership of an ADU when the property changes hands, the Building Department will be able to monitor transfer of ownership through their receipt of title search requests. When a title search is received, the Building Department will issue a letter notifying the new owner that they are required to re-register the Accessory Dwelling Unit with the Building Department whether they intend to collect revenue or not.

Why will this make the village more affordable?

Accessory Dwelling Units help diversify the range of housing options available. Housing affordability is connected to supply and demand. By increasing the supply of housing, it helps control rental rates. Accessory Dwelling Units are by nature small, and therefore more affordable than larger units. To be clear, ADUs will not “solve” the affordable housing crisis we are experiencing. It will, however, start to move us in the right direction.

What other proposals were there to make living in the village more affordable?

There have been several large housing developments proposed that have not received approval in recent years. The Village approved the construction of the YMCA complex by the Wilder Balter development firm which will increase the number of affordable units in the Village. The purpose of the ADU legislation is not solely to increase the supply of affordable units in the Village, but also to give individual homeowners options to help with affordability, including senior citizens who are living on reduced incomes.  In addition, ADUs accommodate family members that can live with, but separate from, one another such as an aging parent or a college graduate. 

Would an ADU be allowed on my street?

Accessory Dwelling Units are permitted in all single-family residential zones, but whether an ADU is permitted on a given property depends on the property and the type of ADU proposed.  

The list of other locations in Westchester is a small sample size and shows a relatively small number of ADUs. How has it helped make it more affordable if there are so few of them?

The ADU legislation is meant to be just one tool in the toolkit to address the housing affordability problem. It is not meant to be the only response.

What about reducing taxes to increase affordability?

Village taxes only account for 25% of the property tax burden. The majority of property taxes go to the school district. Nevertheless, the Village continues to make efforts to keep the tax levy steady while delivering the level of service expected by residents. To be clear, however, expanding the Village’s tax base in ways that don’t place significant burdens on existing resources is also a way to reduce taxes.

If the goal is to create affordable housing how does the village plan to regulate rent? If not, the assumption is rent will be market driven. If that is the case, what is the average rent for a unit comparable to a typical ADU and more importantly, how will this meet the primary objective of the initiative?

There are two major objectives of the legislation. It is designed to increase the availability of affordable housing in the Village, and it is also meant to help residents age in place instead of having to leave the Village after they retire. The Village does not regulate rents. It will be up to the homeowner and the market to set the rental price. But the small nature of the units and the increase in supply should help keep rental rates in check.  If a resident needs to access government subsidy to build out a unit then the unit will come with a government requirement to rent at an affordable rate.  The owner of the property will be governed by the subsidy provider to maintain affordability. 

Will the addition of an ADU be considered an improvement that will increase the valuation of the property (assessment) thereby increasing the primary owner’s property tax rate?

Yes. Improvements made to a home including the addition of an accessory dwelling unit will likely increase the assessed property value of the home.

Does the village anticipate additional tax revenue?

If the assessed property value of a home increases with the addition of an Accessory Dwelling Unit, then tax revenue may slightly increase which will help accommodate additional residents.

Who are the members of the Task Force and what is their role (representatives from the village, residents, business owners etc).

The Members of the Housing Affordability Task Force are listed here:

The bios of the members of the Task Force can be found here:

The role of the Housing Affordability Taskforce is to identify opportunities to create more housing and affordability in the village and make recommendations to the Board of Trustees in support of those opportunities. 

Does the village anticipate demand for ADUs in Tarrytown from neighboring communities?

The demand for ADUs will likely be the same as any rental apartment.

Am I to infer that this effort means the demand for market-based housing has diminished and the town will therefore not advance new market-based construction?

The ADU legislation is just one tool in the toolkit for increasing the availability of housing in the Village. It is also meant to provide homeowners who wish to remain in their homes but may need assistance doing so as they age a way to accomplish that goal. The Village continues to receive proposals from developers for market-based housing and will consider each one as it comes forward.  The demand for housing across the region is incredibly strong and Westchester County is behind in providing new units to keep up with demand.

 How many properties in the village currently meet the eligibility requirements set forth in the legislation and do you have a layout map?

Accessory Dwelling Units will be permitted in all single-family residential zones. The Zoning map for the Village can be found here. Given the number of possible iterations of Accessory Dwelling Units and an exponential number of factors, it is not practical to determine eligibility for every property.

What avenues/opportunities do neighboring properties have to comment on a proposed ADU?

The concept of permitting ADUs within the Village is not a new one. Permitting ADUs was an explicit recommendation of the Village’s Comprehensive Plan; one that was widely supported by throughout the development of the Plan. Subsequent to the adoption of the Village’s Comprehensive Plan, the Housing Affordability Task Force made several presentations to the Board of Trustees on the topic of affordable housing and ADUs before legislation was even drafted.

An application for an individual ADU is subject to site plan approval, and therefore community comment, in the following circumstances:

  1.  a new addition to an existing one-family dwelling is created for the ADU and the addition increases footprint, square footage or FAR triggering the requirement for Planning Board site plan approval under § 305-132(A)(1);
  2. an existing garage is converted to an ADU resulting in the need for on-site parking triggering the requirement for Planning Board site plan approval under § 305-132(A)(2);
  3.  there is a change, addition or modification to land or buildings designated as an historic district or historic landmark by the Village Board triggering the requirement for Planning Board site plan approval under § 305-132(A)(3); and/or (ii) Architectural Review Board approval under § 9-4(A)(4). 

If an ADU is installed within the footprint of an existing structure excluding the above circumstances, necessary building permits will be required but notification of neighbors will not be required.

What is the application process a tenant will need to complete and how will the Village ensure adherence to fair housing practices? 

The Village does not get involved with adherence to fair housing practices for other rental units in the Village, and nor will it do so in the case of ADUs. If there is a complaint regarding fair housing practices, it is handled by the Westchester County Human Rights Commission.

One of the illustrations in the presentation depicts a lower lever/basement unit. Given issues the area has had with flooded basements during severe rain, is this an area of concern? 

Accessory Dwelling Units are required to conform to building codes and safety requirements. This legislation should help alleviate some of the illegal construction that causes harm to health and safety.

Can a multiple-family home that presently exists in a single-family zone add an ADU? Can they add one per living unit? Can they add it in an out building or as part of the existing structure?

No. A multi-family home grandfathered into a single-family residential zone cannot add an accessory dwelling unit.

Can a property owner develop an ADU in an out-building that does not have a 3 foot setback on an existing non-conforming lot?

It depends on the out-building. Fire safety and building codes would require renovations that will often make a non-conforming out-building cost prohibitive such as the installation of a sprinkler system and the need to make the structural elements non-combustible.

Is the village going to allow and consider applications for variances for allowing ADU's that don't fit the present proposal?

All property owners have the right to go to the Zoning Board of Appeals.

What are you going to do with attached garages?

If the minimum of two parking spaces required for the principal residence are removed in the installation of an Accessory Dwelling Unit, the property owner will be required to submit the proposal to the Planning Board for site plan review.

What conditions make a garage fireproof?

The walls of the garage need to be made of fire-rated materials and/or a fire sprinkler system needs to be installed. It depends on the structure.

What are you going to do about driveway blockage in an emergency situation?

The issue exists currently and should not significantly change with the enactment of this legislation.

Where will the extra garbage go?  

The same rules for how trash and recycling are treated will continue to apply.

Where will the extra vehicles go?

Every property is different.

How are you going to monitor sublets?

The Village does not monitor sublets. The 6-month minimum lease requirement will apply to ADUs and compliance will be enforced as it is currently by the Building Department's Code Enforcement officer.

How will you measure success of the program?

The program will be considered a success if units are added to the supply of housing in the village. In addition, if illegal apartments are made legal, and compliant with building codes and safety regulations, the program will be deemed a success.

Other Resources on Accessory Dwelling Units

AARP on Accessory Dwelling Units

Shelterforce Series on "ADUs Explained"

American Planning Association on ADUs


For more information about the Accessory Dwelling Unit Legislation being proposed, you can access the draft legislation, the presentation from the Housing Affordability Task Force, and other information on the Village HATF webpage. The Public Hearing on the proposal will continue at the February 8, 2023 Board of Trustees Meeting.