Basement finishing in Westchester

Westchester is not on the state Department of Health's list of 40 high radon area counties, though neighboring Putnam and Dutchess are, and the department still recommends testing all homes.¹³ The EPA recommends testing for radon on the lowest lived-in level, so a basement that hasn't been tested should be tested before it is remodeled; fixing a radon problem is usually easier and cheaper before the basement is finished.¹⁴

The New York State Department of Health advises testing for radon every five years, every two years if the home has a mitigation system, and also when buying a home and after major renovations.¹⁵ A state test kit costs $12¹⁵. The EPA's guidance is to fix your home if radon tests at 4 picocuries per liter or higher, and to consider fixing it between 2 and 4.¹⁶

Before turning basement space into living space, the EPA advises checking it for leaks and other signs of moisture and fixing any moisture problem first, because damp basements promote mold and other biological growth.¹⁴ The EPA warns that carpet on a basement slab can stay damp from water or vapor coming up through the concrete, or from room moisture condensing on a slab that is colder than the air, and either can lead to mold.¹⁴

For the inside of basement walls, Building America calls for rigid foam fully adhered to the foundation with sealed seams, or spray foam, and rates closed-cell spray foam as the best moisture control of the interior options.⁷ ENERGY STAR's guidance for existing homes, based on the 2021 IECC, is R5 insulating sheathing or R13 batts on basement walls in climate zone 3, R10 sheathing or R13 batts in zones 4A and 4B, and R15 sheathing or R19 batts in zones 4C and 5 through 8.¹⁷ Have the company name the climate zone and the wall build-up on the permit drawings, so the inspector and the crew work from one plan.

Because finishing a basement changes how air moves through a house, the EPA advises having a professional check afterward that new and existing combustion equipment is not backdrafting.¹⁴ That matters in the many Westchester basements where an oil boiler and water heater share the space.

In Mamaroneck's A flood zones, the lowest floor of a home must sit at least two feet above the base flood elevation, and enclosed areas below grade on all sides count as basements and are not permitted.¹¹ In New York, a building that is substantially improved, meaning the work is valued at more than half of the structure's market value, falls under the same floodplain development rules as new construction.¹²

The Village of Mamaroneck counts substantial improvement cumulatively, adding up improvements over ten years against the 50 percent of market value that brings a building under its flood rules.¹¹ A finished basement can tip that total even when the job itself seems modest. Floodplain management in New York is run locally: work in a FEMA special flood hazard area needs a floodplain development permit from the municipality, whose designated floodplain administrator is usually the building inspector.¹²

Your municipality enforces New York's residential code, which is built on the national model; the numbers here are the model's, so ask the building inspector to confirm them. The 2021 IRC requires habitable space and hallways, including the parts of a basement that contain them, to have a ceiling at least 7 feet high, and bathrooms and laundry rooms at least 6 feet 8 inches.¹⁸ In a basement with habitable space, beams, girders, ducts and other obstructions may hang down to within 6 feet 4 inches of the finished floor.¹⁸

The 2021 International Residential Code requires at least one operable emergency escape and rescue opening in a basement, plus one in each sleeping room, including every bedroom in a basement.¹⁸ Under that code, an escape opening needs a net clear opening of at least 5.7 square feet, at least 24 inches high and 20 inches wide, with its bottom no more than 44 inches above the floor.¹⁸ An escape window whose bottom sits below the ground outside needs an area well of at least 9 square feet, at least 36 inches out from the wall and 36 inches wide, big enough for the window to open fully.¹⁸

A finished basement with a kitchen is a different project. Westchester municipalities each write their own accessory apartment law, and two of the laws read for this guide bring in the county health department. Before New Castle issues a building permit for an accessory apartment, the Westchester County Department of Health and the Town Engineer must approve its water and sewage, and a separate water meter is required where feasible.¹⁹

More than one in four adults 65 and older fall each year.²⁰ Basement stairs in older houses are often steep and open on one side. Finishing the space is the time to add a second rail, switches at the top and bottom, and treads that contrast with the floor. NAHB's Certified Aging-in-Place Specialist (CAPS) credential trains remodelers in home modifications for aging in place.²¹

The number on this page reaches one independent company that handles basement finishing in the Westchester area, and the call is recorded. What gets built, when and for how much is between you and that company.

The company pays us for the call. You pay us nothing, and we don't call or text you later. How we make money

Westchester County's Department of Consumer Protection licenses home improvement contractors and requires plumbers and electricians to hold a county trade license to work in the county.²² Westchester County tells consumers to ask plumbers and electricians to show their county license card, which shows when the license expires, or to search the county's online list of licensed tradespeople.²³ Check a New York license

A New York homeowner may cancel a home improvement contract until midnight of the third business day after signing, by written notice that shows they don't intend to be bound; the right doesn't apply when the owner called the contractor for a bona fide emergency and signed a handwritten waiver.²⁴