NJ Sump Works Blog · Updated September 2026

How Much Does a French Drain Cost in NJ?

Short answer: an interior French drain in NJ typically costs $4,000-$8,000 for a full basement perimeter ($50-$80 per linear foot), while an exterior system runs $8,000-$15,000+. Here's exactly what goes into the price.

Interior vs. Exterior French Drain Costs in NJ

These are two different jobs with two very different price tags. An interior French drain runs inside the basement, along the inside of the foundation walls just under the floor slab. In North Jersey, a full-perimeter interior system runs $4,000 to $8,000 installed.

An exterior French drain is installed outside, around the foundation at footing level, intercepting groundwater before it reaches the wall. That means excavating around the house — often 6 to 8 feet deep — which is why exterior systems typically cost $8,000 to $15,000+. For most wet basements the interior system is the better value: about half the cost, a day or two to install, and no torn-up landscaping, patio, or driveway.

How Linear-Foot Pricing Works

French drains are priced by the linear foot because the work scales with the trench length. In NJ:

Interior: $50-$80 per linear foot installed. Exterior: $100-$150 per linear foot, because excavation, soil hauling, and backfill are labor-heavy. A typical NJ basement perimeter measures 100 to 150 linear feet — that's how you get to the $4,000-$8,000 interior range. Many homeowners only need a partial perimeter (one or two problem walls), which can bring an interior job down to $2,500-$4,000. We measure your basement during the free inspection and price exactly what you need. In Paterson or Passaic, where high water tables keep basements wet year-round, a full perimeter is usually the right call.

What's Included in the Price

A complete interior installation includes: breaking a strip of concrete floor along the wall, digging the trench below slab level, laying perforated pipe bedded in washed gravel, covering it with filter fabric to keep silt out, tying into a sump basin with a working pump, repouring the floor flush, and hauling all debris. The finished floor looks like we were never there — just a clean seam along the wall. Wayne and Hackensack homeowners often ask whether a basic drain is enough; usually it is, but pairing it with a battery backup pump (see our sump pump warning signs guide) protects you when the power goes out.

What Drives the Cost Up

Several factors push a French drain quote higher. A finished basement costs more because drywall, flooring, and baseboards must come out along the wall before trenching. Exterior obstructions — decks, patios, driveways, buried utilities — add excavation cost to exterior systems. Depth matters: deeper footings mean deeper trenches and more soil to haul. Adding a new sump pump and basin runs $1,200-$2,500 on its own, and a battery backup adds more — but it's the difference between a system that works and one that works during a blackout. Upgrades like a wall vapor barrier or second discharge line also add cost but pay off in dryness. That's one reason a general basement waterproofing cost estimate varies so widely — a French drain is one component, and the extras add up.

How to Know You Need a French Drain

Water pooling where the wall meets the floor is the classic sign — groundwater rising under your slab and finding the cove joint. Recurring puddles after every heavy rain, dampness that never dries, and efflorescence (white mineral crust) on the lower walls all point to water pressure under the floor. In Clifton and river-adjacent towns, the water table sits high enough that some basements seep even without rain. If you're mopping up more than once a year, a French drain isn't a luxury — it's the permanent fix. Our free inspection includes a moisture check that tells you in minutes whether drainage is the answer or something simpler (like grading) will do.

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