How To Fix Basement Water Issues When Digging Outside Isn’t an Option

When water starts creeping into your basement, garage, or other below-ground spaces, the first thought is usually: “How do we keep it out?” Ideally, we’d install a drainage system outside the foundation, but that’s not always possible.

Maybe your yard is too tight to excavate. Maybe there’s a porch or patio in the way. Or maybe you just don’t want to rip up your landscaping.

The good news? There’s a great solution from the inside.

An Interior French Drain—Under the Slab

If we can’t get to the outside of your foundation, we can install a version of a French drain system underneath the concrete floor, right inside your basement or garage.

This method follows the same water management principles as a traditional French drain but is installed entirely below the floor slab. Here’s how it works:

How It’s Installed

1. Cut & Remove the Concrete

We start by cutting back about 12 inches of the concrete slab along the edges where water is coming in. This gives us access to dig a trench below the floor and foundation footing.

2. Install the Drain System

• A shallow trench is dug, slightly sloped toward a collection point.
• We add a layer of gravel, then place a perforated PVC pipe inside the trench.
• More gravel is added on top of the pipe, stopping a few inches below the slab level.

3. Add the Sump Pump

To remove the water, we install a sump pump inside the space:

• A section about 3 feet by 3 feet is cut out of the slab.
• We dig a hole and place a 15-gallon sump basin surrounded by gravel to allow water to flow in freely.
• The pump inside the basin automatically turns on when needed and pumps the water out through a buried pipe that drains into the yard—far away from your home.

4. Pour New Concrete

Once everything is in place, we re-pour concrete to cover the trench and pump area, leaving you with a finished surface again.

Optional Wall Drainage (for Persistent Wall Leaks)

If water is also coming through the basement walls, we can install an angled drainage strip along the edge. This creates a small gap that directs wall moisture into the drain. We can also add a wall covering to help guide water down into the system, keeping the space clean and dry.

This step isn’t always required, but it’s helpful for homes with stubborn wall seepage.

Concerned About Radon?

If your home has radon concerns, don’t worry. We can modify the system to make sure it doesn’t create new paths for radon gas to enter your home. Drainage and radon mitigation can absolutely work together when designed properly.

The Bottom Line

If water is coming into your basement or slab-level space and digging up the yard just isn’t possible, an interior French drain with a sump pump is an effective, proven solution. It’s discreet, durable, and handles water before it becomes a bigger issue.

We Can Help

At Upstate Structural Repair, we design interior drainage systems tailored to your space—no guesswork, no pressure. We’ll inspect your home, walk you through the options, and offer a free estimate to help you make the right decision.