Installing an interior French footing drain

An interior French drain doesn’t prevent water from entering your basement. Rather, it catches water that seeps inside and channels it by gravity to a sump pump that sends the water back outside or into a drain line.

To install an interior French drain, a waterproofing contractor cuts a channel into your basement slab around its perimeter. The contractor excavates the ground below the channel, installs perforated drain pipe and a sump pump well, and fills the trench with drainage gravel. The slab is patched with fresh concrete.

Advantages:

  • Doesn’t disturb exterior landscaping
  • Basement is readily accessible in all weather, so work proceeds on schedule
  • Costs less than an exterior footing drain

Disadvantages:

  • Can’t stop wall seepage (so applying wall finishes remains problematic)
  • Sump pump won’t function during electrical outages without battery or generator backup
  • Cutting concrete is messy and noisy

Cost: $3,000 to $4,000.

Installing an exterior French footing drain

An exterior footing drain is one of the surest wet basement solutions. It’s also one of the most expensive. Because this system requires a thorough excavation to expose your foundation walls and footings, it gives you the opportunity to apply a waterproof coating or membrane to the exterior surfaces of your walls for added protection.

To install an exterior footing drain, a waterproofing contractor digs around the outside of your foundation with a backhoe. The contractor applies waterproofing to your basement walls, then installs a French drain system next to the foundation footing. The excavation is filled with gravel to promote drainage.

If your lot is sloped, the drainage will flow by gravity to an exit point or a storm drain system. Otherwise, you’ll need an exterior sump pump to move the water away from your house.

Advantages:

  • Waterproofs basement walls from the outside
  • Large excavation ensures good drainage next to the foundation
  • Removes water before it can enter basement

Disadvantages:

  • Working a backhoe around your property may destroy landscaping features
  • All plantings at the dig site will be removed
  • Expensive

Cost: $9,000 to $15,000 (including waterproofing walls).

John Riha is a HouseLogic managing editor. He’s been a residential builder and was the executive editor of Better Homes and Gardens magazine. He’s hand-built a French drain system and notes, “It’s a heck of a lot of digging.”