When a basement leaks along its walls, contractors generally suggest one of two approaches: fixing it from the outside or managing the water from the inside. Here's how they compare.
Exterior waterproofing
The contractor digs down along the outside of the foundation to the footing, cleans the wall, applies a waterproof membrane or coating, and usually installs new exterior drain tile before backfilling.
- Pros: stops water at the wall before it touches the concrete; no work inside the finished space.
- Cons: usually much more expensive; tears up landscaping, decks, patios and driveways along the wall; hard where homes are close together; doesn't address water rising from below the floor.
Interior waterproofing
A strip of the basement floor is removed along the walls, drain tile is laid beside the footing, and water is routed to a sump pump. A membrane on the wall often guides seepage down into the system.
- Pros: generally costs less; handles both wall seepage and water rising from below; can be done in any season; no exterior digging.
- Cons: water still reaches the outside of the wall; requires opening the floor and the bottom of finished walls; depends on a working sump pump.
Why interior is more common here
In many Twin Cities neighborhoods, the problem is groundwater pushing up at the floor joint as much as water through the wall. Interior systems handle that, at lower cost and with less disruption to the yard. Exterior work still makes sense for a single problem wall that's easy to reach, or for a wall that needs structural repair from outside anyway.
Whichever you choose, fix the easy outside items too: downspouts, grading and window wells.