Waterproofing

Basement water problems are never "just a little dampness." Untreated, they become mold, framing rot, finished-basement loss, and reduced resale value. The fix depends entirely on whether water is coming through the wall, under the slab, or from a failed drainage system above.

Waterproofing sits at the intersection of building science, local code, and what your property actually needs over the next 20 years. Gotham Home Services has been doing this work across all five boroughs and both Long Island counties for years, and we've seen every failure mode the climate, the soil, and the previous contractor can deliver. That history is why we approach every waterproofing job the same way: figure out what the substrate, the structure, and the codebook all require, then deliver work that meets every one of those — not just the cheapest path through.

If you're reading this page you're probably weighing two or three contractors against each other, trying to figure out which one is being honest about scope and price. Our answer is straightforward: we tell you exactly what the job needs, we put it in writing with line items, and we don't change the number after the work starts. Below is the full picture of how we run waterproofing projects — the why, the materials, the steps, the mistakes other crews make, and what it actually costs in 2026.

Brooklyn brownstones and Queens detached homes have very different water issues — brownstones typically need vault and front-wall sealing; Queens needs interior French drains for high water tables.

Material selection is where most waterproofing projects are won or lost. The wrong-grade material costs 10–15% less up front and fails in a fraction of the expected service life — that's not a hypothetical, it's the failure pattern we see every week when we get called in to fix someone else's recent work. The materials and specs we use on waterproofing jobs aren't the most expensive on the market, but they are the right grade for the loads, the climate, and the substrate they're going on.

Every waterproofing job we run uses the spec below as the baseline. When the site conditions call for an upgrade (heavier traffic, problem soils, exposure, historic-district compatibility) we'll quote the upgrade explicitly and explain why. When the site conditions allow a downgrade without affecting service life, we'll quote the downgrade and pass the savings through. The point is that the spec matches the job, not the other way around.

One thing that separates real contractors from "guys with a truck" is that real contractors follow a documented process on every job, in the same order, every time. The waterproofing sequence below is what every one of our crews runs — not what we wish they'd do, what they actually do. If a step is skipped, the job doesn't pass our internal QC and it doesn't get billed as complete.

We share this process publicly for two reasons. First, so you know what to expect: when you book waterproofing with us, the steps below are the steps that happen, in this order, with photo documentation at each milestone. Second, so you can use it to evaluate any other quote you're considering. Ask the contractor across town what their process is — if they can't answer in this much detail, that's information.

We get called in to fix recent waterproofing work all the time — sometimes a year after the original install, sometimes within weeks. The mistakes are remarkably consistent, and almost all of them are avoidable with proper training and a no-cut-corners attitude on site. If you're vetting contractors, the list below is what to look for and what to ask about.

Some of these mistakes are technical (wrong mix, wrong gauge, wrong substrate prep). Others are procedural (no permit, no written warranty, no insurance certificate). And a few are commercial red flags — pressure to sign today, large up-front deposits, "cash discounts" that conveniently leave no paper trail. We've never asked a customer for cash, we don't take more than a reasonable mobilization deposit, and we don't pressure anyone to decide before they're ready.

Waterproofing stops new water. Existing mold needs separate remediation. We coordinate both. Exterior is more permanent but costs more and disrupts landscaping. Interior is faster, cheaper, and handles most residential cases effectively when paired with a proper sump and drain.

Waterproofing pricing in 2026: $400–$1,200 per crack for polyurethane injection, $80–$150 per linear foot for interior French drain with sump, $150–$300 per linear foot for exterior membrane installation.

Pricing for waterproofing is driven by a handful of variables that we lay out plainly in every quote. Two jobs that look identical from the curb can price very differently once you account for sub-grade condition, access, permit requirements, and finish level. That's why we don't give blind phone quotes — a 5-minute site visit is the difference between a number you can trust and a number that grows once the work starts.

Whatever the final number ends up being, it's documented before any work begins. Line-item scope, materials by spec, labor, permit, disposal, and any allowances all show up on the estimate. Change orders (when they're needed) are written, signed, and priced before the change happens. You never get a surprise invoice at the end.

Ongoing maintenance on waterproofing is straightforward when the install is done right. The schedule below is what we recommend to every customer — follow it and the work we deliver lasts the full design life.