French Drains: What They Are, How They Work, and When Your Home Needs One

If your basement smells musty after a storm, or your yard turns into a swamp every spring, you’re not alone—especially here in Colorado. Between our expansive clay soils and freeze-thaw cycles, moisture buildup is a persistent problem. That’s where a French drain comes in.

What Is a French Drain?

A French drain is a sloped trench filled with gravel and containing a perforated pipe that collects and redirects excess water away from vulnerable areas—like your foundation, basement, or yard. It’s a practical solution to prevent water from pooling near your home and seeping into places it doesn’t belong.

Despite the name, French drains aren’t from France—they were named after Henry Flagg French, an American farmer who popularized this drainage method in the 1800s.

Over the years, this system has become a go-to drainage solution, also known as a drain tile, footing drain, or weeping tile. Regardless of the name, the goal remains the same: protect your home from water intrusion.

Why This Matters in Colorado

Colorado’s weather can shift dramatically from dry spells to sudden downpours, especially during the late spring and early summer rainy season. In the Denver metro area, this seasonal shift often brings heavy thunderstorms, saturated soil, and flash flooding—all of which put pressure on your home’s foundation. Without adequate drainage, water can collect near the base of your home and find its way inside, resulting in moisture issues or a full-blown flooded basement.

That’s why it’s critical to have a system in place, like a French drain, that actively redirects water away from your property before it causes damage.

How Do French Drains Work?

A French drain works by creating a pathway of least resistance for water. As water saturates the ground, it naturally finds its way into the gravel-filled trench. From there, it flows into the perforated pipe and is carried away—either to a sump pit, daylight drain, or other safe discharge point.

Depending on where the water is coming from, there are two main types of French drains.

Interior French Drains

Installed along the inside perimeter of a basement, interior French drains are a highly effective solution for managing water that enters your home below ground.

Why Choose an Interior Drain?

If your basement experiences flooding, damp walls, or floor seepage, an interior French drain can prevent long-term damage. It captures water before it reaches your living space and directs it to a sump pump for safe removal.

How It’s Installed

We cut a narrow trench along the inside edge of your basement slab, place a perforated pipe inside a bed of gravel, and connect it to a sump pump system. Once installed, the system is concealed with new concrete.

Interior French Drain Benefits:

Less invasive than exterior systems
Cost-effective
Easier to maintain
Ideal for existing homes

Exterior French Drains

Exterior French drains are placed along the outside perimeter of your foundation. They intercept groundwater and surface runoff before it can pressure or penetrate the basement walls.

Best Use Cases

If your yard floods during storms, your downspouts overflow, or your foundation is frequently damp, an exterior French drain may be the best solution.

Installation Notes

Exterior French drains require excavation down to the footing level, which can disrupt landscaping, patios, or driveways. After trenching, we install filter fabric, gravel, and perforated piping. This is backfilled and graded to promote runoff away from the foundation.

Exterior French Drain Benefits:

Protects the exterior of your foundation
Helps with poor yard drainage and slope issues
Reduces hydrostatic pressure

What Type of Drain Is Right for You?

There’s no one-size-fits-all solution. At Pinnacle, we assess each home based on:

Drainage source (interior seepage vs. surface water)
Foundation condition
Landscape slope and grading
Basement usage (finished vs. unfinished)
Soil type and frost depth

We may recommend one type of French drain, or a combination of both, depending on the situation.

Signs You Might Need a French Drain

Not sure if a French drain is necessary? Here are a few common red flags:

Flooded Basement: Even occasional water seepage can lead to mold, structural issues, and costly damage.
Standing Water in Yard: Water that pools near your foundation or in low spots can erode soil and find its way inside.
Foundation Cracks or Shifting: Persistent moisture against foundation walls can weaken their integrity over time.
Mold or Musty Smell: Chronic dampness, especially in a finished basement, is a health and safety risk.
Soil Erosion: If heavy rain washes away mulch, grass, or topsoil, your property may benefit from added drainage support.

Why Professional Installation Matters

French drains might look simple on paper, but proper installation is critical. Poor slope calculations, lack of filter fabric, or incorrect pipe placement can lead to system failure—or worse, exacerbate your drainage issues.

At Pinnacle Structural Services, we design every French drain system to handle Colorado’s unique soil movement and moisture patterns. We use commercial-grade materials and engineer each solution based on the specific challenges of your property.

Protect Your Home from a Flooded Basement

A professionally installed French drain is a long-term investment in your home’s safety, value, and structural stability. Whether you’re dealing with soggy soil, a flooded basement, or water-damaged landscaping, we’re here to help.

Pinnacle Structural Services is Denver’s trusted partner for foundation repair, waterproofing, and drainage solutions. Reach out today for a custom inspection and learn how we can help you keep water where it belongs: outside.