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Basement waterproofing cost

Interior waterproofing — drain tile plus a sump pump — costs $2,300 – $7,500 for most basements ($65 – $130 per linear foot). Full exterior excavation and membrane work runs $8,000 – $26,000. Often a $350 – $900 crack injection or $600 of grading fixes the actual leak; here is how to tell which job you have.

Interior drain system $2,300 – 7,500 The most common fix
Exterior excavation $8,000 – 26,000 Membrane at the wall
Fix the gutters first $100 – 600 Solves more leaks than you’d think
By Dana Keller, 14 years estimating structural repair Reviewed by Marcus Oyelaran, PE · Last updated July 30, 2026

What basement waterproofing costs

An interior drainage system — perimeter drain tile feeding a sump pump — costs $65 – $130 per linear foot, which lands most basements at $2,300 – $7,500. Full exterior excavation with a waterproof membrane costs $95 – $210 per linear foot, usually $8,000 – $26,000.

Before either: a surprising share of “wet basement” calls are solved by $100 – $600 of downspout extensions and regrading, or by a single $350 – $900 crack injection. Rule those out first — a waterproofing company rarely will.

Basement waterproofing cost by line item

Basement waterproofing costs by component, US national, 2026
Line item Typical range Unit What drives it
Downspout extensions & regrading $100 – $600 per project DIY-able. Fixes many "wet basements"
Crack injection (single leak) $350 – $900 per crack When one crack is the whole problem
Interior sealant / waterproof paint $40 – $90 per gallon Cosmetic damp control only
Interior drain tile + sump $65 – $130 per lin. ft Slab thickness, discharge run
Sump pump (installed with system) $1,000 – $3,500 per pump Pit excavation, discharge plumbing
Battery backup sump system $900 – $2,500 per system Storm power loss protection
Exterior waterproof membrane $95 – $210 per lin. ft Excavation depth, landscaping
Exterior French drain $50 – $120 per lin. ft Trench depth, gravel and pipe
Egress window (with well) $3,000 – $6,500 per window Cutting the wall, code compliance
Dehumidifier (basement grade) $1,300 – $2,800 per unit Installed with drain line

Source: Compiled from published 2025–2026 contractor cost datasets and waterproofing supplier pricing, normalized to installed cost including labor. Linear-foot prices assume a standard 8 ft basement wall. · Last reviewed July 30, 2026 · Reference data · How we compile these figures

Interior or exterior — which system do you need?

Interior vs exterior basement waterproofing, US national, 2026
System Installed cost Scope What it actually does
Interior drain tile + sump $2,300 – $7,500 typical basement Manages water that enters. Solves most chronic seepage
Exterior membrane + drainage $8,000 – $26,000 typical basement Stops water at the wall. For structural damage or finished space

Source: Totals assume a typical 120–170 linear foot basement perimeter. Exterior pricing varies most with excavation depth and what has to be removed and replaced above ground. · Last reviewed July 30, 2026 · Reference data · How we compile these figures

Interior systems accept that water reaches the wall and manage it: collect at the footing, route to a pit, pump it out. They solve most chronic seepage at roughly a third of the exterior price, and they can be installed year-round without touching your landscaping.

Exterior systems stop water before it reaches the wall. They are the right call when hydrostatic pressure is damaging the structure, when the wall itself is deteriorating, or when a finished basement cannot tolerate any water entry at all.

Most contractors sell what they install. On a five-figure quote, an independent inspection ($300 – $600) pays for itself by telling you which system your specific water source calls for.

Try the cheap fix first — seriously

Water in a basement comes from somewhere, and the somewhere is often above ground. Walk the perimeter during the next heavy rain and look for:

  • Downspouts dumping at the foundation. Extensions cost $20 – $50 each and should discharge 6+ feet out.
  • Soil sloping toward the house. Grade should fall about 6 inches over the first 10 feet. Regrading runs $100 – $600 DIY.
  • Clogged or undersized gutters. A blocked gutter concentrates a roof’s worth of water at one corner.
  • One identifiable crack doing all the leaking. Inject it for $350 – $900 — see crack repair cost.

If the basement stays dry through a full wet season after those fixes, you have saved several thousand dollars. If it does not, you now know the water is coming through the wall or up through the slab, which is exactly the diagnosis a drainage system is designed for.

What you can do yourself

DIY-able: regrading, downspout extensions, crack injection kits ($60 – $150), interior sealant paint ($40 – $90 per gallon), and swapping a sump pump into an existing pit ($150 – $600 for the pump).

Contractor work: perimeter drain systems (they require breaking and re-pouring the slab), exterior excavation (trenching against a foundation without shoring is genuinely dangerous), and anything involving the structural condition of the wall itself.

A note on sealant paint: it manages surface dampness and does nothing about water under pressure. Sold as a waterproofing solution, it is the most common way homeowners spend $200 to postpone a real diagnosis by a year.

Does insurance cover any of this?

Waterproofing itself, no — it is preventive maintenance, excluded everywhere. Water damage is covered only for sudden internal events like a burst pipe, not for groundwater seepage or surface flooding (which needs separate flood insurance). The full breakdown is in will homeowners insurance cover foundation repair.

Related: sump pump installation cost, basement repair cost, and the cost calculator if water is coming through a crack.

Frequently asked questions

Interior drain tile with a sump pump — the most common fix — costs $65–$130 per linear foot, or $2,300–$7,500 for a typical basement perimeter. Exterior excavation with a waterproof membrane costs $95–$210 per linear foot, usually $8,000–$26,000 total. Single-crack injection is only $350–$900.

Interior systems manage water that gets in — they collect and pump it out, and solve most chronic seepage for a third of the price. Exterior membranes stop water at the wall and are the right call for hydrostatic pressure damaging the structure, or when a finished basement cannot tolerate any water entry. Most contractors sell what they install; an independent inspection ($300–$600) is worth it on a five-figure quote.

No — waterproofing is preventive maintenance and excluded. Water damage itself is covered only for sudden internal events (a burst pipe), not for groundwater seepage or flooding, which needs separate flood insurance.

You can handle the cheap end: regrading soil away from the wall ($100–$600 DIY), extending downspouts ($20–$50 each), sealing minor cracks with an injection kit ($60–$150), and interior sealant paint ($40–$90 per wall). Perimeter drain systems and excavation are contractor work — trenching against a foundation is dangerous without shoring.

These are estimates, not quotes. Figures reflect 2026 US market data reviewed on July 30, 2026. Actual prices vary with soil, access, local labor rates and the scope a licensed contractor defines after inspecting your property. foundationsage doesn’t perform, schedule or warranty repair work.