A French drain is a ditch in the ground, inset with a perforated pipe under a layer of gravel. That pipe funnels storm water away from where you don’t want it—along the foundation, for example—and deposits that water in a more desirable place.

Depending on the reason for the moisture problem, the fix could be a simple remedy, or it could require a foundation contractor. If you’re looking at waterproofing basement walls, these tips will get you started.