What Is A French Drain? Different Types, How It Works, & Benefits

If you’ve landed on this blog, you’re probably dealing with some water issues in your basement. Or maybe your front yard turns into an impromptu swimming pool every time it rains.

What Is A French Drain? - Image 1

Or hey, maybe you're simply here to quench your thirst for waterproofing wisdom in which case, we respect it.

Whatever the reason, this article will describe and discuss everything you need to know about French drains: what they are, how they work, interior vs. exterior, and more. Let's get into it.

What is a French Drain?

French drains are a drainage system designed to redirect water away from your house. It involves a trench that's filled with gravel or rock, with a perforated pipe placed at the bottom. The trench is strategically positioned in areas where water collects, such as along the foundation of a house or around the perimeter of your basement.

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And before you start dreaming of croissants and baguettes, let’s clarify something: French drains were not designed by our friends over in France. They’re named after the inventor, Henry Flagg French, a Massachusetts lawyer, and farmer who developed the concept in the mid-19th century.

Important to note: There are several names when referring to French drains. Most people refer to it as a “French drain”, but sometimes it’s called a basement drain, weeping tile, perimeter drain, drain tile, and footing drain.  

French drain's entire purpose is to prevent drainage problems and water damage. It creates a path for water to flow away from, which reduces soil erosion and basement flooding.

The perforated pipe is designed to prevent debris from clogging it. And the gravel surrounding the pipe acts as a filter that moves the water where it needs to go while preventing pesky soil particles from getting in.

How do French drains work? Interior vs. exterior

In order to explain how French drains work, we first need to identify the two different types: interior and exterior. They both serve a distinct purpose and work differently.

Interior French drain

An interior French drain is typically installed inside the basement or crawl space, along the perimeter of the foundation walls. It's designed to intercept and redirect water that enters your home, effectively managing basement flooding and preventing moisture-related problems.

Installing An Interior Drainage System

Purpose of an interior French drain

Interior French drains address water issues that occur inside your home, such as basement flooding, moisture, and water seepage. By collecting water before it reaches the basement floor, they help to keep the interior space dry and prevent water-related damage.

Accessibility & installation

Interior French drains are usually more accessible for maintenance and repairs since they're installed inside. This accessibility makes it easier to monitor the drain system and address any potential issues.

The installation of an interior French drain involves cutting a trench along the interior perimeter of the basement floor. The trench is then filled with gravel and a perforated pipe, which collects and carries water to a sump pump or drainage system for removal.

What's the cost of an interior French drain?

The cost of installing an interior French drain can vary depending on factors such as the size of the basement, the complexity of the install, and any additional features required, like a sump pump. Overall, it's typically less expensive when compared to exterior French drains.

Exterior French drain

An exterior French drain is installed outside of the foundation walls, typically around the perimeter of the building. It helps to manage water that collects around the foundation and redirects it away from the property. 

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The purpose of an exterior French drain

Exterior French drains address water issues that occur outside your home, such as surface water runoff, groundwater infiltration, and moisture around the foundation. They help to protect the foundation from water damage, prevent soil erosion, and maintain a stable environment.

Landscape & installation

Installing an exterior French drain requires excavation around the foundation, which can disrupt landscaping, walkways, and other outdoor elements. It's important to consider the impact on your home's exterior during installation. 

After the soil is excavated around the foundation and the trench is dug, the installation of an exterior French drain involves placing a perforated pipe in the trench, adding gravel, and covering with fabric to prevent soil intrusion. The trench is then backfilled with soil.

How much does an exterior French drain cost?

The cost of an exterior French drain installation can be higher compared to interior drains due to the excavation and additional materials required.

Is one better than the other?

Naturally, you're probably wondering which method is better to keep water out. 

Benefits of a French drain

  • French drains effectively manage water and prevent damage to your foundation, basement, or landscaping.
  • They can be installed in various locations and environments and can adapt to different property types and drainage issues.
  • French drains are more affordable to install and maintain than alternative drainage systems.
  • French drains are virtually invisible once installed and covered.
  • They are durable and are a long-term drainage solution.

How to know if you need a French drain

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Basement flooding: If your basement floods or gets wet after heavy rains, then water is clearly finding its way into your home. Moisture can lead to serious damage, including structural issues, mold growth, and compromised indoor air quality. A French drain can help redirect the water away from your foundation, preventing basement flooding and keeping your space dry.

Standing water in the yard: Does your yard or garden turn into a mini pond after rain showers? If your soil has poor drainage, a French drain can effectively collect and divert any excess water, allowing your yard to dry out more efficiently and preventing potential water damage.

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Soil erosion: Soil erosion can wash away valuable topsoil, and damage the health of your landscape. Installing a French drain can mitigate erosion by channeling water away from vulnerable areas, preserving the integrity of your soil, and protecting your landscaping investment.

Foundation problems: Water pooling near your foundation can affect its stability. If you observe cracks in the foundation walls, sinking or shifting of the foundation, or signs of moisture damage, it's
a clear indication that water is negatively impacting your foundation. A French drain, strategically placed around the foundation, will intercept and divert water, preventing potential foundation issues and safeguarding the structural integrity of your property.

Not all French drains are created equal

French drains can be very effective. However, not all French drains are created equal and the quality of installation can significantly impact its effectiveness. 

Installing a French drain requires technical knowledge and expertise. We highly suggest hiring a professional contractor to perform this work. Installing a French drain yourself, though tempting, can end up costing more in the long run if done incorrectly. 

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Here at Thrasher, we use an interior, below-floor French drain system called the WaterGuard. The big difference between WaterGuard and every other French drain system is WaterGuard sits on top of the footing, instead of alongside it. This is important because it keeps the wet dirt (aka mud) from getting into the drain. WaterGuard works to capture that wall and floor seepage before it reaches your basement floor. Small holes, called weep holes, are drilled into every concrete block on the base of your wall. Now, once water collects in the concrete walls, the WaterGuard track effectively captures it. 

After we install the system, we pour brand new concrete to conceal it completely. 

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Protect your home with a French drain

A French drain is an effective and versatile drainage solution designed to manage excess water and prevent water damage to your home. Whether you are dealing with a soggy yard, a wet basement, or erosion issues, a French drain can help mitigate these problems and protect your property. 

If you're in our service area and interested in learning more about our French drain process, our team at Thrasher Foundation Repair is here to help. With our expertise in basement waterproofing, we'll ensure your home is protected from water intrusion. Contact us today by starting a chat in the bottom right corner, filling out this form, or calling us at 1-844-948-3306.


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