Guides
ADU questions and answers
Quick answers to what homeowners ask most. Each links to a guide with the details and sources.
Basics
What is an ADU, and what kinds are there?
An ADU (accessory dwelling unit) is a second, smaller home on the same lot as a house, with its own kitchen, bathroom, sleeping space and entrance. It can be a detached backyard cottage, an addition attached to the house, a converted garage, an apartment over a garage, or a unit inside the house, such as in a basement. You may also see "JADU" (junior ADU), a California term for a small unit inside a house; New York has no such category. Your town decides which of these types it allows.
How is an ADU different from a tiny home, park model, modular home or manufactured home?
"ADU" describes how a home is used: a legal second home on a lot with a main house. A modular home is built in a factory to the same state code as a site-built house, while a manufactured home is built to a separate federal HUD standard. A tiny house is a very small permanent home, and a park model is a recreational vehicle meant for seasonal use, not year-round living. Modular, manufactured and tiny homes can serve as ADUs where zoning allows; a park model usually can't.
Can a park model or a tiny home on wheels be my ADU?
Usually not as a year-round home. Park model RVs are built to a recreational standard and federal rules say they aren't meant for permanent living, so most towns won't issue a certificate of occupancy for one as a home. A tiny house on wheels can qualify only if it was built and certified to a dwelling standard and your zoning allows it. Check the unit's label and ask your town's code office before you buy.
Can someone live in an ADU full time?
Yes, if it is a legal ADU: allowed by your town's zoning, built to the building code, and given a certificate of occupancy. Campers and park model RVs usually can't be legal year-round homes, because they're built for temporary or seasonal use. Some towns also limit who may live in an ADU, such as family members only, so read your town's rules.
What sizes and floor plans are common, and which fit typical rules?
Most ADUs are studios, one-bedrooms, accessible one-bedrooms or two-bedrooms, and one-bedrooms are the most common in the survey data we've seen. Your town's size cap, bedroom limit and lot coverage rule decide what fits, and those vary widely around Rochester. Our concept homes show a range of sizes, but check your town's cap, and how it measures square footage, before you choose one.
Rules
How long do permits take, and what do they cost?
Each town sets its own fees and review times, and we found no state deadline for reviewing a building permit. If a board has to approve your project, such as for a special use permit or a site plan review, state law limits how long it can take once it has your application. A county review can add up to 30 days if your lot is near a town, village or city line, a county or state road, or a farm. Ask for the fee schedule, the meeting calendar and the submission deadlines on your first call to the town's code office.
What happens if I need a variance or a public hearing?
A variance is permission from the zoning board of appeals to break a zoning rule. An area variance bends a measurement, such as a setback, and is possible for a small, reasonable request; a use variance allows a use the district doesn't permit and is very hard to win. Hearings are publicly noticed, neighbors can speak, and anyone harmed by the decision can challenge it in court within a short window afterward. If you need a variance or expect opposition, talk to a land use lawyer.
How long does an ADU take, from first call to move-in?
As rough planning ranges, not promises: about 9 to 18 months where your town requires a special use permit (a board's approval, usually after a public hearing), and possibly under a year where an ADU is allowed with just a building permit. A variance, septic problems or a neighbor's lawsuit can stretch it to two years or more. Under New York Town Law the special use permit alone can take a little over four months, and contractor-built new homes averaged 11.7 months from permit to finish in 2025. Your town's meeting calendar and your builder's schedule set the real timeline.
What are the steps, in order?
Roughly: check with your town's code office that an ADU is allowed, get drawings made, get any zoning approval your town requires, get a building permit, line up utilities (septic or sewer, water, power and a free 811 call before digging), build with inspections along the way, and get your certificate of occupancy, the town's OK to move in. Zoning comes first, because a "no" from the town turns the rest into wasted money. No one may legally move in before the certificate of occupancy is issued.
Are ADUs allowed in my state?
It depends on the state. Some states have laws that make towns allow ADUs, but New York does not, so every city, town and village here writes its own rules. Our state ADU law pages explain each state's rules in plain words, with sources and the date we last checked.
Do I need my HOA's approval, and what if my deed has restrictions?
Possibly. An HOA rule or a deed restriction can limit a lot to one home, ban rentals or require design approval, even where zoning allows an ADU. A few states override HOA bans on ADUs, but we found no New York law that does, so a valid covenant likely still controls. Read your deed, title policy and any HOA documents before you design, and have an attorney review anything unclear.
Are ADUs allowed in my town, and how do I find out for sure?
In New York your city, town or village decides, and a village can have different rules from the town around it. Find your zoning district on the town's zoning map or your tax bill, then read the ADU or "accessory apartment" section of the zoning code, which many towns post on ecode360, and note the date the online code was last updated. Then call your town's code office to confirm whether an ADU is allowed outright, needs a special use permit, or isn't allowed. Get the answer in writing before you pay for plans.
Can I put an ADU on my lot?
It takes three checks: what your zoning allows (district, setbacks, lot coverage, height and size), what the land allows (septic or sewer, well, wetlands, flood zones and slope), and what private rules allow (deed restrictions, easements and HOA rules). A current survey, a call to the code office, the FEMA flood map and the state DEC's wetland mapper answer most of it at low cost. Our property checker walks you through the first questions, and links you to the research we have for your property.
How big can my ADU be?
Your town sets the limit, because New York has no statewide size rule. Near Rochester the limits vary a lot: the Village of Fairport caps ADUs at 650 square feet, while the Town of Clarkson allows up to 30% of the main home's living area, and many towns also cap bedrooms. Ask how your town measures size, since footprint, floor area and living area are counted differently.
Do I have to live on the property to rent out the ADU?
It depends on your town. New York has no statewide rule either way, and many upstate codes require the owner to live in the main house or the ADU, sometimes with a signed affidavit, as the Village of Pittsford and the Town of Clarkson do. Others, such as the Village of Fairport's ADU section, have no such rule. An owner-occupancy rule can also affect who will buy your home later, so ask how it works if you move or sell.
What permits do I need, and who gets them?
Every ADU in New York needs a building permit, and many also need zoning approvals such as a special use permit, site plan review or a variance, plus septic or sewer, water and electrical sign-offs. The homeowner is usually the applicant for zoning approvals, and the builder usually files for the building permit with proof of workers' compensation coverage. A homeowner acting as their own general contractor files a BP-1 form instead, which comes with strict limits.
Money
How much does an ADU really cost, all in?
The total depends on the kind of ADU, the site, utilities, design and approvals, and what the construction price includes. Published national figures mix conversions with new construction and do not establish a price for your property. Compare the complete scope, including site work and utility connections, and get an itemized estimate before committing to a project. Our cost guide explains the main line items and how to compare quotes.
What does the base price include, and what do I pay for separately?
It depends on how the price is quoted. A factory unit price often covers only the structure, with delivery, crane, foundation, utility hookups, permits and site work on top, so the installed price runs far higher. A turnkey price should cover everything needed to move in, but ask in writing about steps, decks, the driveway, tree removal, long utility runs, septic work and fees. Compare every quote at the same level.
How do people pay for an ADU?
Most homeowners use some mix of savings, a home equity line of credit (HELOC) or home equity loan, a cash-out refinance, or a renovation mortgage that lends on what the property will be worth once the ADU is done. FHA, Fannie Mae and Freddie Mac now let lenders count part of an ADU's rent as income in some cases, within tight limits. Talk to two or three lenders and ask whether they will finance a new detached ADU. This is general information, not lending advice.
Are there grants or incentives for ADUs in New York?
The main state program is the Plus One ADU grant, run by NYS Homes and Community Renewal through local partners for income-eligible homeowners who live on the property. At our last check in October 2026, no local partner served Monroe or Ontario County, so most Rochester-area homeowners can't use it yet. New York also lets towns, counties and school districts offer a property tax break for new ADUs, called RPTL 421-p, if they choose to adopt it. The ADU Incentive Act you may read about is a bill, not a law.
Will an ADU raise my property taxes?
Usually yes, because a finished ADU adds market value and your assessment follows it. New York lets cities, towns, villages, counties and most school districts choose to offer a tax exemption on the value a new ADU adds (RPTL 421-p), phasing out over ten years, but each taxing body decides on its own. Ask your assessor whether it has been adopted where you live, and apply before the taxable status date.
Will an ADU raise my home's value?
Often it adds value, but there is no reliable figure for upstate New York, and most studies come from California. A permitted ADU with a certificate of occupancy helps at resale, while an unpermitted one can put off buyers, lenders and appraisers. Where few homes with ADUs have sold nearby, an appraiser may not credit the full cost of building one, so be wary of any flat percentage you see quoted.
What could I earn renting an ADU, and what will it cost to run?
As a local starting point, HUD's Fair Market Rents for the Rochester metro (Monroe, Livingston, Ontario, Orleans and Wayne counties) in its 2025 fiscal year were $1,116 for a studio, $1,256 for a one-bedroom and $1,573 for a two-bedroom, including utilities; in rural Yates County a one-bedroom was $836. No one can promise what your ADU will rent for, so ask a local property manager for an estimate. Then subtract the real costs: loan payments, higher property taxes, landlord insurance, any utilities you cover, upkeep, empty months, and income tax on the rent. Our renting and taxes guide covers the landlord rules and the tax side.
Building
What foundation does an ADU need?
Common choices are a slab with frost walls, a frost-protected shallow foundation, a crawlspace, piers or helical piles, and a full basement. Footings must sit below your town's frost depth or be insulated so frost can't reach them, and New York allows the insulated shallow kind only for buildings that stay heated. A full basement usually costs the most because it takes the most digging, but your soil, slope and groundwater decide what works, so get a quote for your lot.
What does site prep involve, and is my lot ready?
Site prep usually means a survey, clearing and grading, digging the foundation, trenching for water, sewer or septic and power, and a way in for equipment. Before anyone digs, your builder calls 811, and you should hire a private locator for lines you own, like a wire to a garage, because the utilities won't mark those. A factory-built unit also needs room for a truck and crane, so walk the path with your builder early.
Does an ADU need its own septic system, or will I have to upgrade mine?
It depends on your system and the office that reviews septic systems where you live: the county health department in Monroe, Livingston, Genesee and Seneca, or the NYS Department of Health’s Geneva District Office in Ontario, Wayne and Yates. New York sizes septic systems by bedrooms, so adding an ADU's bedrooms means asking whether the existing tank and field can carry the load; it may need to grow, or the health office may want a separate system. Required distances from wells, water and buildings can also decide where a detached ADU can sit. Have the system checked before you design anything.
How do water, power and sewer get connected? Can the ADU have its own meters?
Many ADUs branch off the main house's water, sewer and electric lines, often with a subpanel in the ADU fed from the house panel. Some utilities allow or require a separate service and meter, which costs more up front but makes renting simpler, so ask your water supplier and electric utility early. In New York, billing a tenant through your own electric submeter needs state approval first, so check before you plan on it.
Can an ADU be off-grid or run on solar?
Solar panels can be part of an ADU's design, like any house. Going fully off-grid is harder, because New York's code requires every home to have a toilet, sink, tub or shower and a kitchen sink, so the unit still needs a working water supply and an approved septic system or sewer connection. If off-grid matters to you, ask your town and the office that reviews septic systems (in Ontario, Wayne and Yates counties, the NYS Department of Health’s Geneva District Office) what they will accept before you design.
What building code does an ADU follow, and who inspects it?
Outside New York City, every ADU must meet New York's Uniform Code, including its residential and energy codes, whose 2025 editions took effect at the end of 2025. Your local code enforcement officer reviews the plans, inspects the work in stages and issues the certificate of occupancy. For a modular unit, a state-approved agency inspects it in the factory and each module carries a state Insignia of Approval, so the local inspector checks the foundation, hookups and site work.
Factory-built or built on site: which is better for me?
Neither wins everywhere. Building on site gives the most design freedom and suits attached units, conversions and tight or sloped lots, but more of the work happens outdoors and in sequence. Modular construction moves much of the work into a factory where weather can't delay it, but it needs a clear path for a truck and crane and locks in your design and deposit early. Compare installed prices, not unit prices.
Will an ADU hold up to Finger Lakes winters?
A code-built ADU here has to be designed for our climate. Most of the Rochester and Finger Lakes area is in New York's climate zone 5, which sets high standards for insulation, windows and air sealing, and each town sets the snow load a roof must carry and the depth footings must reach. Heating cost depends on size, insulation and equipment. As checked October 9, 2026, New York's Department of State still lists the new-building fossil-fuel provisions as suspended by court order; ask your code office which current rules apply before choosing heating equipment.
Can I customize the layout and finishes?
With an ADU built on site, nearly everything can be designed around your lot, your house and the person who will live there, within your town's rules and the building code. Factory-built units come in set plans with a menu of options, and changes after the factory slot is booked tend to be expensive. Either way, settle the design before you apply for the permit, because changes during construction have to go back to the town's code office.
What warranty comes with an ADU, and what does New York law already give me?
Builder warranties vary, so get yours in writing before you sign. New York requires a written contract for most home improvement jobs over $500, listing the work, the dates, a payment schedule and your right to cancel within three business days, though it may not cover a brand-new detached ADU. New York's General Business Law also sets an implied warranty for many new homes, and whether it applies depends on how your job is contracted. A lawyer can tell you which protections cover your project.
What does delivery day look like for a factory-built ADU on a rural lot?
The modules arrive by truck and a crane lifts them onto a foundation that was built ahead of time. The truck and crane need a firm, clear route: wide enough roads, no low wires or branches, a manageable driveway slope, and level staging space next to the foundation. Cranes must keep well clear of power lines, so you may need the utility's help on set day, and the route shouldn't cross your septic field or well. Have the crane company walk the site before you sign.
What is Finger Lakes ADU, and are the homes real projects?
Finger Lakes ADU is an educational resource for ADU laws, planning and small-home ideas. The craft archive shows existing homes and woodwork, not ADUs; our concept homes are original illustrations, not finished builds or approved plans. Whoever you hire, ask to see completed projects, talk to past clients and get a written contract.
Living with an ADU
What insurance do I need, especially if I rent the ADU?
Call your insurance agent before anyone moves in. A standard homeowners policy usually won't cover a unit you rent out, so a long-term rental typically needs a landlord policy or endorsement, and tenants should carry renters insurance for their own belongings. Regular short-term renting is treated more like a business, and New York's short-term rental law sets its own coverage minimum. Ask whether the ADU is covered as part of your home or as a separate structure, and get the answer in writing.
How long will an ADU last, and what upkeep does it need?
A permanent ADU built to the code on a proper foundation is built like a house and needs the same care: roof and gutters, caulk and paint, heating and ventilation service, and working smoke and carbon monoxide alarms. In our winters, keep snow clear of egress window wells and outdoor heat pump units, and keep the path to the door cleared. Test for radon after move-in.
Can an ADU be designed for an aging parent?
Yes, if your town and your lot allow an ADU. Plan one level with a step-free entry, 32-inch clear doorways, a curbless shower, room to turn a wheelchair and wood blocking in the bathroom walls for future grab bars, which cost little on the drawings and a lot once the walls are closed. A single ADU usually doesn't have to meet federal accessibility rules, so these choices are yours. Some towns near Rochester allow an ADU only for relatives, or expect it to come out later, so ask your code office before you design.
Can I rent out my ADU?
Only if your town allows it, and many upstate towns add conditions, such as requiring the owner to live in the house or the ADU, or allowing the unit only for relatives. If you rent on a regular lease, New York's landlord rules apply to you, including a security deposit of no more than one month's rent. Short-term rentals face their own town rules and, since March 2025, New York sales tax on stays over $2 a day. An ADU built with the state's Plus One grant must be permanent housing, not a short-term rental.
Can I sell the ADU separately from my house?
Usually not. An ADU sits on the same lot and tax parcel as the main house, so it is sold with the house; a separate sale would need the lot split or turned into condominiums, and many local codes forbid that outright. We found no statewide path to do it in New York, so talk to a real estate attorney if this matters to you.
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