The longer answer

Why water picks that exact spot: your basement floor and foundation wall were poured at different times, so there's a cold seam where they meet. When the clay outside is saturated, hydrostatic pressure pushes water down the wall face and under the footing — and the cove joint is the easiest way in. It's almost never a "crack" you can patch; sealing the seam from inside just makes the water find the next gap, because the pressure is still there.

The question that decides the fix: why is the soil next to your wall saturated?

  • Downspouts dumping at the foundation — the #1 cause we find on cove-seepage calls. One downspout can deliver hundreds of gallons per storm into a few square feet of clay. Burying the extensions ($300–$700 per line) is the cheapest fix on this page and often the whole answer.
  • Grade sloping toward the house — settled backfill tilting the first few feet of yard at the wall. See regrade vs French drain.
  • Water arriving from uphill — a neighbor's slope or a whole backyard draining at one wall. A French drain ($25–$60/LF, most systems $1,500–$3,800) intercepts it before it reaches the foundation.
  • Genuinely high water table — water rising even in dry spells. This is the one case where interior drain tile and a sump system genuinely earn their keep.

About the $10,000–$15,000 interior waterproofing quote: interior systems don't stop water entering your foundation — they catch it after it's inside and pump it out. Sometimes that's genuinely necessary. But it's the last resort, not the first quote, because in most KC homes the water supply outside can be cut off for $300–$3,800. Get the outside fixed first; if seepage persists after the water path is corrected, then the interior conversation is honest. We'll tell you plainly which case you have — we don't sell interior systems, so we have no reason to steer you there.

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