Find a licensed basement waterproofing company on Long Island

What basement waterproofing companies do

Basement waterproofing keeps water out of the basement: grading and gutters outside, crack repair, drains along the footings, sump pumps, and coatings or membranes on the walls.

• Water on the basement floor after heavy rain.
• Damp walls, white mineral deposits or a musty smell.
• Before finishing a basement, so the new rooms stay dry.

Who licenses basement waterproofing companies on Long Island

Suffolk County

• Waterproofing is named in Suffolk County's home improvement law, and the law makes a county license mandatory for the businesses it regulates, unless exempt.
• Basements and waterproofing both appear on Suffolk Consumer Affairs' list of home improvement work.
• Work in the electrical and plumbing fields is excluded from Suffolk's home improvement definition.
• A waterproofing contractor working without a license in Suffolk is subject to arrest and prosecution, Consumer Affairs warns.

Nassau County

• Nassau's Administrative Code names waterproofing as home improvement work, and no one may run a home improvement business in the county without a license.
• Waterproofing is on Nassau County Consumer Affairs' list of who must be licensed.

Step by step: how to check a basement waterproofing company's license in Suffolk or Nassau.

Town by town

Each town page quotes that town's own rules for basement waterproofing, with the date we read them.

What it costs

Labor is a large part of any price. Long Island construction laborers earn a median $58,875 a year, from about $39,468 at entry level to $79,154 with experience. Cement masons and concrete finishers earn a median $65,026 a year, from about $53,234 at entry level to $82,344 with experience. (New York State Department of Labor, wages updated to the first quarter of 2026.)

Waterproofing prices turn on where the water comes from, whether the fix is outside or inside, how much of the floor or wall is opened, and whether a sump pump and drain are added. See the basement waterproofing cost guide.

What to ask before you hire

• Your county license number, so I can check it before I sign?
• A certificate of insurance sent to me by your insurer, not a photo?
• Where is the water coming from, in writing, before you sell me a system?
• Would grading, gutters or downspout extensions fix it for less?
• Does the work need a permit, and where will the sump pump discharge?
• What does the warranty cover, and does it transfer if I sell?

How Revival helps

Request a free call. Revival goes over the job and the permit with you, checks licenses and insurance, and introduces up to two vetted, licensed basement waterproofing companies as they join our network. You choose who to hire, and you never pay Revival.