A French drain is a gravel-filled trench with a perforated pipe that allows water to automatically drain from your lawn. If water is accumulating in your basement, a french drain is a great way to prevent damage to your house. A french drain, when properly built, will help keep your basement dry and avoid potential water damage.
French drains are used as an alternative to gutters to prevent ground and surface water from destroying building foundations. Bad drainage is the most common source of collected water.
When you suspect an excessive amount of humidity in your building or find water penetration, you'll need to start thinking about replacing or repairing your french drain.