Video:What Is a French Drain?

Transcript:What Is a French Drain?

Hi, my name is Sarah Ray, landscape architect, for About.com. Today I'm going to explain what a French drain is, how it is used and what to avoid when installing one.

Why Should You Install a French Drain?

The primary reason for installing a French drain is to prevent standing or subsurface water from causing serious structural damage to your home or property. Standing or subsurface water can cause foundation damage; flooding in your basement, crawlspace and garage; retaining wall failure; buckling of walkways and driveways. And all of these things are very expensive to repair or replace.

Example of Where You Need a French Drain

This is a French drain I installed on this property -- the reason it needed a French drain was because this entire crawlspace was wet and saturated with water. The grading around the house was causing runoff from the hill and from the garden, and was pooling along the foundation. This corner in particular was saturated with water because this downspout was dumping here and it was just pooling.

What a French Drain Looks Like

So a French drain is a gently sloping gravel-filled trench with connecting perforated drain pipes wrapped in filter fabric. It uses gravity to draw water away from a structure to a discharge point -- ideally to the street. Though the concept of the French drain is simple, installing one isn't. Be prepared for some serious back-breaking work, or be willing to hire a professional company that specializes in drainage issues.

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