Basement finishing in Wilmington

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 EPA's Map of Radon Zones places New Castle County in Zone 2, moderate potential, while Kent and Sussex counties to the south are in Zone 3.³ 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 4.¹³

Delaware's Division of Public Health offers Delaware residents a free radon test kit through its Radon Office, and notes that radon levels can differ between neighboring homes, so each home has to be tested.¹⁴ The Division of Public Health warns against relying on a basement fan or an open window to lower radon and recommends a radon contractor who installs sub-floor suction and venting.¹⁴

If a system is needed, route the vent pipe and choose the fan spot while the ceiling is still open, then test again once the room is finished.

Wilmington's sewer system is a combined system that carries both stormwater and household wastewater, and heavy storms can push that mix into nearby waterways.¹⁵ When a downpour fills those pipes, a floor drain or a basement toilet is the lowest opening in the house.

For a sewer backup in a house or neighborhood, Wilmington tells residents to dial 311 inside the city, or 302-576-2620 from outside it, or to file a 311 request online.¹⁵ Before finishing a city basement, ask a plumber whether the house drain has a backwater valve and whether one suits your connection.

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 a basement with habitable space, beams, girders, ducts and other obstructions may hang down to within 6 feet 4 inches of the finished floor.¹⁶ In a low rowhouse cellar, the floor joists and the main drain usually set the finished height, and digging the floor down is structural work.

When an existing basement is altered, the 2021 IRC requires escape openings for any new bedrooms created there, but not for the rest of the remodeled space.¹⁶ 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 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 Those are model-code figures; Wilmington building permit plans go to the Department of Land Use and Planning by email, and work must follow the 2018 International Building and Residential Codes along with the city's own codes.¹¹ Ask your own permit office which edition it enforces.

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.¹⁷ 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 8.¹⁸ Get the insulation values in writing and confirm the permit drawings show the same wall assembly.

More than one in four adults 65 and older fall each year.¹⁹ Rowhouse cellar stairs tend to be steep and narrow. While the walls are open, add a rail on the second side, light the stair from switches at the top and bottom, and mark each tread nose so it stands out. NAHB's Certified Aging-in-Place Specialist (CAPS) credential trains remodelers in home modifications for aging in place.²⁰

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

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Check the company's state registration before you pay anything. Delaware's public Contractor Registry lookup lists contractors that properly registered and are considered compliant with Department of Labor laws, searchable by name, ZIP code, certification number, NAICS code or industry; a contractor that drops off the list may not have re-registered, may be under review, or may have been suspended or revoked.²¹ Contractors working in unincorporated New Castle County must get a New Castle County contractor license, a permit-endorsed license for work that needs a permit, while electrical contractors are licensed by the State; the county's Contractor License Search shows a contractor's license and authorized trades.²² Check a Delaware license

Ask who will pull the building, plumbing and electrical permits, and get the radon work written into the contract. Delaware's Consumer Protection Unit home improvement regulations, effective November 1, 2023, require a written contract listing all material terms, bar asking homeowners to sign incomplete contracts or calling a binding contract an estimate, require a completion date unless clearly disclosed, and bar getting a certificate of completion before the work is done; contractors must give buyers a copy of the unit's summary of the rules before the contract is signed.²³