Rental conversions on Long Island

Islip grants an accessory apartment permit only if an owner of the lot lives in the main dwelling unit, and the tenants are limited to the accessory unit.⁸ Islip allows one accessory apartment per lot with at most two bedrooms, at least 300 square feet of floor area, and no more than 800 square feet or half of the house's total floor area, whichever is less.⁸ Islip accessory apartment permits must be renewed every three years or when title transfers, with an affidavit of residency and notice to the owners of homes within 100 feet.⁸ In Islip, a house that received its certificate of occupancy after September 1, 1992 must be at least seven years old, counted from that certificate, before it can have an accessory apartment.⁸

To qualify for a Babylon accessory apartment permit, the house must be owner-occupied as the owner's primary residence, have off-street parking for four cars and meet fire and structural requirements.⁹ Babylon also requires the house to be at least three years old, both units to have at least 350 square feet of habitable space and every room at least 80 square feet, and a plumbing permit for the sink in a new apartment's kitchen.⁹ Babylon's accessory apartment permits are temporary exemptions from the zoning law; they must be renewed, and owners reapply three months before the expiration date.⁹

In Nassau, Oyster Bay takes a narrower approach. The Town of Oyster Bay allows parent-child residences, small dwelling units meant for a member of the resident owner's immediate family, such as a parent, child, sibling, grandparent or in-law, rather than an outside tenant.¹² In Oyster Bay, the owner must live in either the main or the accessory unit as a primary residence, only one parent-child residence is allowed per lot, and the accessory unit must be smaller than the main one with no more than two bedrooms.¹² An Oyster Bay parent-child residence must keep the look of a one-family house, both units must share one entrance, doorbell, mailbox and electric meter, and the lot needs at least three off-street parking spaces.¹²

Other towns and the villages set their own terms, so read your own town's law before paying for drawings.

Hempstead rental occupancy permits are valid for two years from the date of issuance.¹⁰ Babylon requires a rental permit whenever someone other than the owner is the primary resident of a home, including family members who pay no rent; in a legal two-family house both units may be rented, but each still needs the permit.⁹

A rental permit and an accessory apartment permit are different things. The first lets someone else live in a legal unit; the second makes the unit legal in the first place.

Suffolk County's Office of Wastewater Management says that building a new home or modifying an existing one may need its approval to confirm the sewage disposal system meets the Sanitary Code, and it has a separate application for the sewage disposal and water supply of an accessory apartment.¹³ Suffolk's Sanitary Code counts as an expanded single-family residence any addition or change that requires new or modified sewage disposal, or that adds bedrooms beyond the number the Department's Office of Wastewater Management previously approved.¹⁴ A second kitchen and a bedroom or two in the lower level is exactly that kind of change.

To qualify for Suffolk's septic improvement grant, the property must be an existing single-family home, two-family home or single-family home with one accessory apartment, with a valid certificate of occupancy, current property taxes and a deed on file with the County Clerk.¹⁵ In Nassau, Oyster Bay's law adds a county health step. Unless the house is connected to public sewers, Oyster Bay requires Nassau County Department of Health approval before, or as a condition of, the special use permit for a parent-child residence.¹²

New York's Plus One ADU Program, funded with $85 million in the 2022–2023 state capital budget, works through local governments and nonprofits to help low- and middle-income owner-occupants of single-family homes build a new accessory unit or bring an existing one up to code.¹⁶ HCR's list of Plus One ADU localities includes the Suffolk towns of Babylon, Brookhaven, Huntington and Islip, and lists no locality in Nassau County.¹⁶ If your town is on that list, the local administrator can tell you whether the grant applies to a conversion like yours.

These are national model code rules; your town applies New York's version, and Islip requires the house to meet its two-family standards. The 2021 IRC requires the units of a two-family dwelling to be separated by walls and floors with at least a 1-hour fire-resistance rating, or a 1/2-hour rating if the building has an automatic sprinkler system throughout.¹⁷

The 2021 IRC requires at least one egress door for each dwelling unit, reached by a continuous path that does not pass through a garage, and opening to a public way or a yard or court that leads to one.¹⁷ On a high ranch that usually means a new side or rear door into the lower level rather than sharing the front stairs. The 2021 IRC requires smoke alarms in each sleeping room, outside each separate sleeping area and on every story including basements, interconnected within each dwelling unit so that one sounding sets off all of them.¹⁷

EPA's lead renovation rule generally doesn't cover homeowners working on their own pre-1978 homes, but it does apply if you rent out all or part of your home.¹⁸ Federal law requires renovation firms working in a rented home to give the renters EPA's Renovate Right pamphlet no more than 60 days before work begins.¹⁹

More than one in four adults 65 and older fall each year.²⁰ Oyster Bay's law is written for family members, and many owners elsewhere build the unit for a parent too. A step-free entrance, a curbless shower and lever handles cost little more if they're in the first drawings. NAHB's Certified Aging-in-Place Specialist (CAPS) credential trains remodelers in home modifications for aging in place.²¹

The number on this page puts you through, on a recorded line, to one independent company that handles rental conversions in the Long Island area. Design, schedule and price are between you and that company.

That company pays us for each call, so connecting costs you nothing, and no one from our side contacts you by phone or text afterward. How we make money

New York State does not license home improvement contractors, but some local governments do, including New York City, the City of Buffalo, and Nassau, Suffolk, Westchester, Putnam and Rockland counties; where a local license is required, the Department of State says to hire only a licensed contractor.²² Nassau County's Office of Consumer Affairs licenses home improvement contractors, and its daily-updated lookup shows each license's status and what work the contractor's insurance does and doesn't cover.²³ Suffolk County's License and Complaint Violation Look Up searches county license records, including home improvement, master plumbing and master electrical licenses, by license number, name, business name, phone or address, along with complaint and violation information.²⁴ Check a New York license

A New York home improvement contractor must deposit payments received before the job is finished as the Lien Law requires, or instead give the owner a bond, contract of indemnity or irrevocable letter of credit, and the contract must tell the owner so.²⁵ Make the town's approval of the apartment a condition of the contract, so construction doesn't start before the board has ruled.