What basement waterproofing costs in Long Island

There is no fixed waterproofing price in this guide, because none of the 20 companies publishes a fixed waterproofing price on its own website. Every dollar figure on this page is a range or a discount found on a company's own site, labeled as such. None of them is a fixed price for every home, and none of them is a quote for your home: final prices depend on the system type, the size of the basement, whether the work is interior or exterior, access, soil and foundation condition, and how much work the job takes, as the companies themselves state.

New sump pump and drainage channel installed in a basement corner

Published figures (labeled, never fixed prices)

LI Basement Pro: interior drainage systems, perimeter drain tile plus sump pump, $4,000 to $12,000, a range; exterior waterproofing membrane, $8,000 to $25,000, a range; sump pump plus battery backup, $800 to $3,500, a range; crack injection, $500 to $1,500 per crack, a range. A typical cost range for interior drainage in Bay Shore, $4,500 to $10,000, is a range, not a fixed price.
Long Island Foundation Co.: crack injection, $500 to $3,000, a range (a single settled vertical crack, $500 to $1,800; multiple active cracks with seepage in Nassau, $1,200 to $4,500); carbon fiber, $4,000 to $12,000 per wall in one section and $4,000 to $8,000 per wall in another, a range in conflict between sections of its own site; wall anchor, $8,000 to $20,000, a range; helical and push piers, $1,800 to $3,000 per pier, a range, with typical jobs of 4 to 10 piers; interior waterproofing with French drain and sump, $6,000 to $12,000, a range; total estimates, $5,000 to $25,000, a range.
Zavza Seal: sealants and coatings, $500 to $3,000, a range; crack injections, $400 to $1,500 per crack, a range; interior drainage system plus sump pump, $5,000 to $15,000, a range; full basement waterproofing system, $8,000 to $25,000 or more, a range; on average, interior waterproofing ranges from $3,500 to $10,000, an average range.
Diamond Masonry & Waterproofing: ranges in conflict between its own pages: interior waterproofing typically costs between $4,500 and $15,000 on one page, typically costs between $3,000 and up on another version of the same page, and interior waterproofing might range from $3,000 to $8,000 while exterior waterproofing can cost $8,000 to $15,000 or more on its Merrick page. All of these are ranges in conflict, never fixed prices.
Discounts, never prices: ACM Basement Waterproofing, 50% off materials on new projects over $10,000, a promotion, not a price; Home Healthy Homes, 15% off any service, a promotion, not a price; HRC Waterproofing, 6% off for first responders, veterans and seniors, a discount, not a price.
Foundation Crack Repair: no fixed price, only a general orientation that minor crack repairs start at a few hundred dollars and major structural work costs more. That is an orientation, not a fixed price and not a system range.
Every other company in this guide publishes no price figure at all. Several offer a free inspection, a free estimate or a free consultation instead.

What drives a waterproofing quote

System type: interior drainage, exterior membrane, or both, and whether a sump pump with battery backup is included.
Basement size and layout: linear feet of drainage, number of walls, and crawl space area.
Condition: cracks, seepage, wall movement, and what an inspection finds.
Access: how easy it is to reach the walls, excavate outside, and run discharge lines.
Scope: waterproofing only, or waterproofing plus foundation repair, such as wall anchors or piers.
Who does the work: the company's own crew or subcontractors, and whether permits, disposal and restoration are included.
Timing: routine service versus emergency service for active water entry, which companies price differently.

What a written quote should itemize

Exact scope: interior system, exterior system, or both, and which parts of the job are included.
How the price is calculated: by job, by linear foot, or as a flat scope price, and what would change it.
Permits and county requirements: which ones apply, who obtains them, and whether fees are included.
Discharge: where the water goes, and whether the discharge line and backup power are included.
Who does the work: the company's own crew or subcontractors.
Total price and what would change it: extra work found during excavation, added parts, or added drainage.
Warranty: what it covers, for how long, and whether it transfers to a new owner.

Ask every company the same questions and compare itemized quotes, not headline figures. The quote-questions checklist on the Get quotes page is built for exactly that comparison.