Basement finishing in Central Jersey

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.¹² NJDEP rates three Middlesex County municipalities Tier 1, its high radon potential category: Highland Park, North Brunswick and Piscataway.³ Even in a low-tier town such as Sayreville, some houses test high, which is why NJDEP asks every home to test. NJDEP recommends that all homes be tested for radon, because levels vary widely even within a tier and homes in low or moderate radon areas can still test high.¹³

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 4.¹⁴ By New Jersey law, every business and professional that tests for radon or installs radon mitigation must be certified by NJDEP.¹³ A fan and a vent pipe from under the slab are far simpler to route before the drywall goes up.

Department of Community Affairs rules require builders to include radon-resistant features in new homes built in Tier 1 areas.¹⁵ A house built in Highland Park, North Brunswick or Piscataway since those towns joined the high tier may already have the passive pipe; an older one may not, so ask whether it can be roughed in while the ceiling is open.

New Jersey's Division of Codes and Standards says finishing an existing basement is an alteration under the Rehabilitation Subcode, and nothing requires raising the existing ceiling to 7 feet just because the space is being finished.⁹ New construction follows a stricter number. 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.¹⁶ In postwar Middlesex basements, the low points are usually the ductwork and the steel girder down the middle.

When an alteration creates a bedroom below the fourth floor, it needs a window or exterior door that meets the subcode's escape-opening requirements, plus a hard-wired smoke alarm in the bedroom and a second one near it.¹⁰ 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.¹⁶ In a raised ranch, the lower windows may already come close to that size; in a full basement, a bedroom usually means cutting a bigger opening and digging a well outside. 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.¹⁶

After the remnants of Tropical Storm Ida, Middlesex County declared a county-wide state of emergency because of flooding and storm damage in every municipality, and water levels in the Raritan River were the highest in 50 years.¹⁷ If your lower level took water in that storm, start with drainage and the flood map before any finishes.

Under New Jersey's flood hazard rules, a regulated flood hazard area and riparian zone exist along every regulated water that drains 50 acres or more.¹⁸ In Woodbridge's A-zone flood hazard areas, new construction and substantial improvement of a habitable building must have its lowest floor, including any basement, and its utilities and service equipment raised to or above the local design flood elevation, confirmed by an elevation certificate.¹¹ Finishing the basement of a house that is being substantially improved can run into that elevation rule, which a below-grade floor rarely meets, so talk to the floodplain administrator before drawings are made.

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.¹² 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.¹² Building America advises keeping fiberglass batts and cellulose out of contact with foundation walls, and not putting polyethylene sheeting, vinyl or foil wallpaper, or epoxy, oil or alkyd paint on the inside of basement walls, because they trap moisture.¹⁹ Flooring that shrugs off damp, such as tile or vinyl plank, is the safer pick on a slab.

More than one in four adults 65 and older fall each year.²⁰ Cellar stairs in older houses are often steep and narrow, and finishing the basement is the moment to fix them: handrails on both sides, switches at top and bottom, and tread edges that contrast with the steps. NAHB's Certified Aging-in-Place Specialist (CAPS) credential trains remodelers in home modifications for aging in place.²¹

The number on this page connects you, on a recorded line, with one independent company that handles basement finishing in the Central Jersey area. What gets built, when and for how much is agreed between you and that company.

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Look up the company's state registration before money changes hands. New Jersey's Contractors' Business Registration Act requires every home improvement contractor business, from a sole proprietorship up, to register with the Division of Consumer Affairs every year before selling or making home improvements, unless the law exempts it.²² The Division of Consumer Affairs' License Verification System is a real-time lookup; its Business Search finds home improvement contractor businesses by business name, license number or city and lists each one's registration number, license type, status and city.²³ Check a New Jersey license

Ask who files the building, plumbing and electrical permits, and consider tying the last payment to a radon test taken after the work is done.