Interior French drain guide

Control water at the perimeter—not after it crosses the floor.

An interior perimeter drain can collect water near the foundation and carry it to a sump basin. Its usefulness depends on correct diagnosis, continuous pitch, suitable stone, and a reliable discharge system.

Signs worth investigating

  • Water repeatedly appears along the wall–floor joint
  • Hydrostatic pressure affects multiple basement walls
  • Surface drainage has been corrected but seepage continues
  • A finished basement requires a planned, serviceable drainage route

What a careful evaluation should cover

  1. Confirm that perimeter groundwater is the likely source.
  2. Map the channel, basin, utilities, structural footings, and discharge route.
  3. Specify clean stone, drainage pipe, wall interface, and concrete restoration.
  4. Require access points and a maintenance plan.

Before approving work

Questions to ask the contractor

  • Why is an interior drain preferable to exterior work here?
  • Will the installation disturb the footing?
  • Can the system be flushed or inspected later?
  • What finishes must be removed and restored?

Continue exploring

WaterproofingFoundation cracksSump pumpsFrench drainsCrawl spaces