“French drain” gets used for two completely different systems, and a lot of confusion on waterproofing quotes comes from that. One goes in the yard. One goes under your basement floor. They solve different problems.
The exterior French drain
A shallow trench in the yard with filter fabric, washed stone and a perforated pipe. It catches water moving through the top couple of feet of soil, or running across the surface, and carries it to a lower spot, a dry well or a storm connection.
It’s for: soggy lawns, standing water against the house, runoff from a neighbor’s lot, wet window wells.
It won’t fix: water coming up through the basement floor or in at the bottom of the wall. That water is deeper than a yard drain reaches.
The interior “French drain”
What contractors often call an interior French drain is really an interior drain tile system. A strip of floor is cut out along the wall, pipe is set in washed stone at the footing, a membrane goes on the wall, and the water runs to a sump pump.
It’s for: water along the bottom of the walls, at the joint where the wall meets the floor, especially after rain and snowmelt.
It won’t fix: water pooling in the yard, or a sewer backing up through the floor drain.
How to tell which you need
- Water in the yard or against the outside of the wall: exterior.
- Water inside along the floor joint: interior.
- Both: often both, starting with the outside, because the cheapest water to deal with is the water that never reaches the wall.
Cost and warranty
A yard French drain depends on the length and where it can discharge, we price it after we see the yard, and it isn’t covered by our waterproofing warranty. An interior drain tile system runs approximately $6,000 to $8,000 for a 40-foot wall, depending on how much wall needs it, and our drain tile and membrane work carries our 25-year transferable limited warranty.
More on French drain installation and interior waterproofing.
We’re Mansour’s Innovations, a waterproofing, excavation and plumbing contractor in Shelby Township, in business since 2014 and working across Macomb, Oakland and Wayne counties. Call (586) 345-7292 for a free estimate. We book from 8 a.m. to 8 p.m. every day and answer emergency calls 24/7.
