Interior French drains
Interior perimeter drainage that collects groundwater and directs it toward the sump system.
The workhorse of interior waterproofing: a channel at the base of the wall that catches water before it spreads across your floor.
What it is
An interior French drain is a trench cut into the slab along the inside perimeter of the foundation, at the level of the footing. Perforated pipe is set in washed stone inside that trench and pitched toward the sump basin. Concrete is restored over the top.
Water that reaches the base of the wall — through the cove joint, through block cavities, up through pressure under the slab — drops into the stone, enters the pipe, and travels to the sump instead of running out onto your floor.
Why interior instead of exterior
An exterior system means excavating around the foundation, which can mean removing decks, walkways, landscaping and utilities. Interior drainage does the same job from inside, is workable year-round, and doesn't disturb the outside of the house. There are properties where exterior work is genuinely the better answer, and we'll say so when that's the case.
What the installation looks like
- The perimeter is marked and the work area is protected
- Concrete is cut and removed in a band along the wall
- The trench is dug to the footing and pitched toward the sump location
- Washed stone and perforated pipe are set in place
- Where block walls are involved, weep openings can be created so water in the cavities can drain out rather than sit
- Concrete is restored over the trench
On the job
Drilling weep holes at the base of the wall
Water sitting inside the cavities of a block wall has nowhere to go. Drilling into the bottom course lets it drain out at footing level, straight into the stone and pipe rather than pooling in the wall.
This is the kind of detail that decides whether a system works in year five. It costs almost nothing to do at installation and is close to impossible to add later.
About interior french drains
How long does an interior drain take to install?
Many single-family basements are a two to three day job, depending on the length of the perimeter, access, and what has to be moved first. We give you a schedule before we start.
How much mess is there?
Concrete cutting is dusty and loud — there's no way around that. We contain the work area, remove the debris, and clean up before the final walkthrough.
Does the whole perimeter need drainage?
Not always. Some basements only need the wet walls addressed. That's a judgment call made during the inspection.
Service area
Local waterproofing, local service
We're based in Schenectady and work across the Capital Region of New York. If your town isn't listed, call and ask — we're likely close by.
- Schenectady, NY
- Albany, NY
- Troy, NY
- Niskayuna, NY
- Rotterdam, NY
- Colonie, NY
- Latham, NY
- Clifton Park, NY
- Saratoga Springs, NY
- Amsterdam, NY
Schedule your free basement inspection
Tell us what you're seeing and where. We'll look at the basement, identify the visible signs of water intrusion, and explain the options in plain language.