What foundation leak repair costs
Most homeowners pay $350 – $900 to seal a single leaking foundation crack, and $2,300 – $7,500 when the leak is chronic enough to need a perimeter drainage system with a sump. Exterior excavation with a waterproof membrane, the most thorough option, runs $8,000 – $26,000.
That is a spread of roughly seventy to one, which is why every honest answer to "what does a foundation leak cost" starts with a question rather than a number. The price follows the source of the water. One crack is a morning of work. Water arriving along the entire footing is a system.
Between those two sits the fix people skip: $100 – $600 of downspout extensions and regrading. Roof water dumped beside a foundation saturates the soil against the wall and finds any weakness in it. A meaningful share of foundation leaks stop when that water is sent somewhere else, and the work is a Saturday with a shovel.
Foundation leak repair cost by line item
| Line item | Typical range | Unit | What drives it |
|---|---|---|---|
| Downspout extensions & regrading | $100 – $600 | per project | DIY-able; resolves a large share of leaks |
| Crack injection | $350 – $900 | per crack | Length, width, access to the wall face |
| DIY injection kit | $60 – $150 | per kit | One dry, accessible, non-structural crack |
| Interior drain tile + sump | $65 – $130 | per lin. ft | Slab thickness, discharge run, obstacles |
| Interior system — typical basement | $2,300 – $7,500 | per basement | 120–170 ft of perimeter |
| Sump pump (installed) | $1,000 – $3,500 | per pump | Pit excavation and discharge plumbing |
| Battery backup system | $900 – $2,500 | per system | Storm outages, when the pump matters most |
| Exterior waterproof membrane | $95 – $210 | per lin. ft | Excavation depth, landscaping to restore |
| Exterior French drain | $50 – $120 | per lin. ft | Trench depth, gravel, pipe, restoration |
| Floor slab crack repair | $500 – $1,600 | per crack | Flooring removal drives the price |
| Structural engineer report | $450 – $600 | per visit | Independent read on cause and scope |
| Permit | $75 – $400 | per job | Required for most drainage and sump work |
Source: Compiled from published 2025–2026 waterproofing contractor cost datasets and supplier pricing, normalized to installed cost including labor. Linear-foot figures assume a standard 8 ft basement wall; the typical-basement totals assume a 120–170 ft perimeter. · Last reviewed July 30, 2026 · Reference data · How we compile these figures
Two lines are worth reading twice. The permit at $75 – $400 shows up on most drainage quotes, and its absence from a bid is a sign the contractor plans to skip the inspection. The engineer report at $450 – $600 is the line most homeowners leave off and most wish they had bought, because it is the only number on the page that comes with no product attached.
Region moves these figures more than any other factor outside the scope itself. Basements in the upper Midwest and Northeast sit deeper and the trades that dig them are busy, so drainage work there tends to land in the upper half of the per-foot range. Slab-on-grade regions across the South and Southwest see fewer perimeter systems and more slab-level repairs, which shifts the same homeowner's bill toward the crack-injection and slab lines instead. Expect a swing of roughly 25 percent either side of the national figures purely on labor rates and how deep the local frost line pushes a footing.
Season matters too, in a way that is easy to use. Waterproofing crews book solid in spring and after the first hard autumn rains, and quotes reflect it. The same job priced in midwinter or midsummer often comes in lower, and a leak you have already diagnosed is a leak you can afford to schedule at your convenience rather than the weather's.
Cost by where the water is coming from
| Where the water enters | Typical cost | Scope | What the fix is |
|---|---|---|---|
| Roof water landing at the wall | $100 – $600 | per project | Downspout extensions, gutter clearing, regrading |
| One identifiable wall crack | $350 – $900 | per crack | Polyurethane injection, done in a morning |
| Window well filling up | $100 – $600 | per well | Well drain, cover, and grade away from it |
| Seepage along the wall–floor joint | $2,300 – $7,500 | per basement | Interior drain tile and a sump pit |
| Water pushing up through the slab | $2,300 – $7,500 | per basement | High water table; relieve pressure under the floor |
| Sump pump that stopped keeping up | $1,000 – $3,500 | per pump | Capacity, check valve, discharge freezing |
| Damp walls with dry floor | $1,300 – $2,800 | per unit | Condensation. A dehumidifier, not a drainage system |
| Structural damage or finished space | $8,000 – $26,000 | per basement | Exterior excavation and membrane at the wall |
Source: Source categories reflect the standard diagnostic sequence used in residential water-intrusion assessment; each is priced with the same installed-cost dataset applied to the repair that source calls for. Multiple sources are common in one basement. · Last reviewed July 30, 2026 · Reference data · How we compile these figures
Notice how far apart the first two rows sit from the fourth. Getting the source right is worth several thousand dollars, and it is the part of the job a homeowner is genuinely well placed to do — you are the one who can be standing in the basement during the rain.
Finding the source costs you nothing but a rainstorm
Watch during the next heavy rain rather than after it. Wet concrete an hour later tells you little; water moving tells you everything. Take a flashlight and a phone, and look for the entry point rather than the puddle, since water travels along the footing before it pools.
- Water at one spot on the wall. Follow it up. A crack, a form tie, or a pipe penetration — all sealable for $350 – $900.
- Water along the joint where wall meets floor. Hydrostatic pressure under the slab. This is what drain tile at $65 – $130 per linear foot exists for.
- Water in a window well. The well drain is clogged or missing. Usually under $600 to correct.
- Damp walls, dry floor, musty smell. Tape a square of plastic sheeting to the wall for 48 hours. Moisture on the room side means condensation — a dehumidifier at $1,300 – $2,800 handles it.
That last test is the highest-value ten minutes in this entire guide. Condensation and seepage look identical on a block wall, and homeowners buy drainage systems for humidity problems every year. The plastic tells the two apart for the cost of the plastic.
What you can do yourself, and what to hand over
Homeowner work: extending downspouts to discharge 6 or more feet from the house, clearing gutters, regrading soil to fall about 6 inches over the first 10 feet, clearing a window-well drain, and injecting one accessible dry crack with a $60 – $150 kit. Together that is a weekend and under $600, and it resolves more foundation leaks than any single product sold for the purpose.
Contractor work: perimeter drain tile, which requires breaking and re-pouring a channel of slab; sump pit excavation and discharge plumbing; and anything involving a trench against the foundation, where an unshored wall of soil is a genuine hazard.
A word on interior sealant paint. It costs $40 – $90 a gallon, controls surface dampness, and is marketed as waterproofing. Against water under pressure it delays the diagnosis by a season and leaves the wall looking fixed while the water keeps arriving. Spend the same afternoon outside with a shovel instead.
Insurance, and where to go next
Standard homeowners policies treat groundwater seepage as gradual, which puts it outside coverage. A sudden burst supply line under the slab is usually covered, because the cause is sudden and accidental. Surface flooding needs separate flood insurance. The distinctions are set out in full on will homeowners insurance cover foundation repair.
Related reading: basement waterproofing cost for the systems side, foundation crack repair cost for a single crack, sump pump installation cost, and the cost calculator for a range built around your perimeter.