What a French drain does
It's a perforated pipe laid in gravel at the foot of the foundation. It collects water from the soil before it pushes against the wall, and carries it somewhere else: a sump with a pump, a ditch, depending on the lot.
Over the years it can clog with silt or roots, get crushed, or fill up with an orange sludge called iron ochre. Some older houses do not have one. Either way, the water eventually finds its way into the basement.
Check before you dig
A damp basement is not always caused by the drain. An eavestrough emptying at the foot of the wall or a yard that slopes toward the house can also let water in, and these problems can be corrected without excavation.
When we suspect the drain, we can often run a camera into it through the sump or a cleanout (see camera inspection). If the pipe is only dirty, cleaning may be enough. If it is crushed, missing or full of ochre, it needs to be replaced.
Replacing the drain and insulating the foundation
We dig along the foundation down to the footing. The wall is cleaned and inspected, a membrane goes on, then the new drain in its gravel bed. With the wall exposed, this is the ideal time to insulate it from the outside, and we recommend taking advantage of the work to do so.
We then backfill and restore the yard. One customer who had us redo their French drain and foundation insulation pointed out that everything had been put back in place afterwards. That is the result we aim for.
Where the water goes, and where it can't
A foundation drain must be connected to the right place. If the house is on a septic system, the Environment ministry's guide is clear: foundation drains and eavestroughs must not be connected to it. Such a connection would needlessly overload the leaching field. Our septic systems page covers the rest.
As for where the water can go on your lot, the municipality often has a say, so check with them. For new construction, plan the drain from the start, along with the foundation excavation. To discuss your project, use our contact page.
