Thinking about installing a French drain to deal with water around your home or in your crawl space? Smart move. French drains are a time-tested way to redirect water away from where it shouldn’t be—like under your foundation or pooling in your yard.
But one of the first questions we hear is: “How deep should it be?”
Let’s break it down.
What’s a French Drain, Anyway?
Quick refresher: A French drain is a gravel-filled trench with a perforated pipe that redirects water away from your home. It works by collecting groundwater or surface runoff and guiding it safely out and downhill—away from your crawlspace, basement, or yard.
Think of it as a hidden water highway under your property.
So, How Deep Should It Go?
Standard Depth: 18 to 24 inches
For most residential applications—like along the perimeter of a house or crawlspace—18 to 24 inches deep is the sweet spot.
- Deep enough to catch groundwater
- Shallow enough to install without hitting utility lines
- Perfect for pairing with vapor barriers or foundation protection systems
Width & Slope Factor
It’s not just about depth. A good French drain also needs:
- Proper width – typically 12 inches wide
- Consistent slope – about 1 percent grade is standard
- Clean backfill – washed gravel or drainage rock prevents clogging
- Fabric wrap – helps block dirt from entering the pipe
What Happens if It’s Not Deep Enough?
If the drain is too shallow:
- It might not catch subsurface water
- You risk freezing in colder climates
- Water can still seep into your foundation or slab
Too deep?
- You may hit utility lines or footings
- Water might bypass the drain entirely and pool elsewhere
DIY vs. Professional Install
French drains seem simple, but getting the slope, trench depth, and outlet position right can be tricky. Done wrong, they clog, fail, or make the problem worse.
That’s why many homeowners call in a pro (that’s us). At Better Basements, we:
- Evaluate water flow
- Choose the best drain depth for your property
- Handle installation, gravel backfill, sump pump connections, and more
French drains are one of the most effective tools for keeping water out of places it shouldn’t be. But to work well, they need to be installed at the right depth—with proper slope, backfill, and outlet placement.
If you need help figuring out the right setup for your crawl space or yard, we’re here to help. Better Basements offers professional French drain design and installation that keeps your home dry, protected, and ready for anything Mother Nature throws at it. Call us today for a free estimate.