What basement waterproofing costs
Interior drain tile costs $65 – $130 per linear foot of wall trenched, and the sump pit and pump it drains into is a separate $1,000 – $3,500 — contractors price those two lines separately, so check that both appear in any bid. Most jobs treat the one or two walls where water actually enters, which puts the typical all-in bill at $2,300 – $7,500. Trenching a full perimeter of 120 – 160 feet is a bigger job at $8,000 – $20,000. Exterior excavation with a waterproof membrane costs $95 – $210 per linear foot, usually $8,000 – $26,000.
That distinction is worth holding onto when a quote arrives. A contractor pricing the full perimeter when water enters at one wall is not necessarily wrong — but they should be able to say why. Ask which walls are in the scope and how many linear feet they priced, then check it against the per-foot rate above.
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
| 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?
| System | Installed cost | Scope | What it actually does |
|---|---|---|---|
| Interior drain tile + sump | $2,300 – $7,500 | one to two walls (35–70 ft) | Manages water that enters. Solves most chronic seepage |
| Interior drain tile + sump | $8,000 – $20,000 | full perimeter (120–160 ft) | Same system, whole basement. Only where water enters all round |
| Exterior membrane + drainage | $8,000 – $26,000 | full perimeter (120–160 ft) | Stops water at the wall. For structural damage or finished space |
Source: Totals are the per-linear-foot rates above applied to the wall length in each row. Most interior drainage jobs trench only the walls where water enters, which is why the typical bill sits well below a full-perimeter figure. 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.