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Water damage from leaking in crawl spaces and basements is a widespread issue that homeowners face, and many people struggle to find a permanent solution. Various things can be done to reduce the chance of water contacting your concrete block walls, but a French drain is one of the most efficient.

While external drainage systems are somewhat costly, they often present ongoing, preventative protection from water seepage. If installed properly, they can solve your wet basement problems and reduce the potential for massive damage to your foundation due to hydrostatic pressure.

In this guide:

  • What a French drain is
  • The different types of French drains and their applications
  • Where to install a French drain
  • A cost guide for French drain installation
  • How to save money on installing a french drain

What Is A French Drain?

A French drain, also called a drain tile or curtain drain, is an underground drainage system that commonly runs around the perimeter of your foundation. It's a type of waterproofing that limits the amount of excess water that comes in contact with your concrete walls. It consists of large perforated pipes that collect and direct water from the soil to a dry well or an area of your property that won’t create moisture issues for your foundation.

If installed outside, the PVC pipes are equipped with a landscape fabric that prevents soil and plant matter from clogging the drain, and they’re usually covered with gravel to help draw water out of the soil and into the drain pipe.

What Are The Different Types Of French Drains?

There are several different kinds of French drain systems, each of which is ideal for different drainage problems and budgets. Below, I’ll discuss the four main types of French drains, as well as some of the pros and cons of each.

Interior

Interior French drains, also referred to as weeping tiles, are placed on the inside of your foundation walls. Installation involves cutting a trench in your concrete slab, installing the drainage pipes, and coupling with a sump pump.

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These trench drains are very effective, but they’re more of a reactive measure, as they only remove water that has already entered your basement. They’re generally not suitable for finished basements, they’re very expensive, and they require the disruption of existing concrete.

Exterior

In contrast, exterior French drains are installed on the outside of your foundation walls. They present a preventative solution, as they move water away from your home before it has the opportunity to interact with your foundation walls.

Exterior drains can be much cheaper than interior drainage systems, but they do still require excavation.

There are two types of exterior French drains - shallow and footing.

Shallow

Shallow French drains are installed just below the ground, so they’re particularly useful for removing excess runoff before it damages your foundation. They’re often the least expensive drainage system to install, as they require the least excavation.

Shallow French drains are visible, so most homeowners cover the catch basis with landscaping features. Because they’re so close to the surface, they can be damaged more easily if they’re forced to bear weight.

Footing

Footing French drains are installed much deeper in the ground, usually next to the footings or base of your foundation. They aren’t visible from the exterior, and they’re much less fragile than shallow drains. They’re excellent options for removing groundwater that causes hydrostatic pressure against your concrete walls.

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Footing French drains are often the most expensive to install because they’re the most labor-intensive, and they’re not as useful for protection against heavy rain given how deep they are.

What Are The Signs You Need A French Drain?

Because French drains are effective at removing rainwater and groundwater, the areas that indicate you need a drainage system will be in your basement or yard.

If you have constant water intrusion issues through your crawlspace or basement walls, including active leaks or excessive moisture, a French drain system is likely to help solve your problem. Additionally, pooling water around your foundation or on patios or driveways, or soggy portions of lawn are good indicators that a French drain is needed on your property.

If any of these problems worsen during or following rainfall, a French drain may be useful for you. 

Where Should You Install A French Drain?

You can install French drains on the inside or around the outside of your foundation walls, but the placement can be optimized based on the water seepage issues you’re having. Choosing the drain placement to fit your specific problem is the best way to ensure a permanent solution, and you should consult with a professional who has experience installing french drains.

Slopes Or Downhill

The soil around your home should be graded away from your foundation at a rate of at least ½” per foot. There are situations, however, in which this isn’t possible or probable. If you have slopes or downhill sections of your yard that lead down to your foundation, a French drain will serve best as a barrier between the slope and your house.

Graded soil will always naturally move water downhill, so placing your French drain parallel with the lowest part of the slope will help ensure that water moving toward your foundation is moved away before it can cause leaking.

Perimeter Of Home

If your crawlspace or basement seems to have constant water seepage problems, especially following storms, a French drain around the perimeter of your home is an excellent option to reduce leaking. Groundwater and rainwater can be rerouted away from your concrete walls with a perimeter drain depending on which type of exterior drain you install.

Basement Floor

Exterior drains are good at removing minimal water from around your foundation, but severe water intrusion and problems with standing water are best solved with an interior drainage system installed around the perimeter of your basement floor. When coupled with a sump pump, these interior drains can remove large amounts of water from your basement once it has leaked through your concrete.

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What Impacts French Drain Installation Costs?

The national average cost of installing a French drain has an extensive range and generally costs between $1,500 and $15,000. Therefore, it’s useful to understand the significant cost factors that determine where in this wide range your total cost will be. Below are some of the larger cost factors involved in the installation.

Trenches

Excavating is often the most expensive part of installing a French drain. Deep excavation of soil for footing trenches will cost significantly more per linear foot than small trenches dug for shallow French drains. Although less expensive than the excavation for footing drains, interior trenches are also very expensive, as they require jackhammering and removing concrete to install the piping and sump pump.

Accessibility

The ease of access to the excavation site will also affect your overall project cost significantly. Landscaping features like patios, decks, driveways, trees, and gardens will make exterior excavation substantially more difficult and expensive.

If you have a finished basement with severe water problems, the demolition of the interior will need to be done to access the concrete slab for a basement floor drainage installation.

Soil Content

Lastly, the contents of your soil will have an impact on installation costs. Slate, shale, expansive clay, and heavy rock content in your soil make excavation more difficult, thereby increasing the price.

What Are The Costs Of French Drain Installation?

The cost to install a French drain depends mainly on the placement, your conditions, and the drain system chosen.

The average cost of an interior French drain is between $50 and $60 per linear foot. Installing an interior drainage system around the basement’s perimeter in a standard, 1,000 square foot home will likely cost around $12,000-15,000.

This number can increase if foundation walls need to be braced before digging the trenches or if your basement is finished and needs to be demolished before work can begin. Sump pump installation will add about $1,000 each, and your basement may need multiple sump pumps depending on the size.

Shallow exterior French drains typically cost approximately $10-15 per linear foot, so installation around a standard, 1,000 square foot home will cost around $3,000-5,000. This cost can increase significantly if excavation is made more difficult by landscaping features or if digging needs to be done manually instead of with a trencher due to utility lines.

Footing drains on your exterior are usually the most expensive at about $80-100 per linear foot. This pricing can increase quite a bit if excavation requires the removal of driveways, patios, or decking or if a landscaper needs to be hired afterward. For a 1,000 square foot home, a full-perimeter footing drain will cost around $20,000 and can be as expensive as $30,000.

How To Save Money On French Drain Installation?

Given the high cost of installation, many homeowners naturally seek ways to save money on installing a French drain. There are several ways to reduce the cost.

Because solving basement water intrusion is challenging to do, getting the job done correctly the first time is critical to prevent paying for additional work down the road. Temporary solutions or DIY drainage systems may seem appealing because they reduce labor costs. However, the best way to save money in the long term is to pay for professional installation from the onset of the issue.

Another great way to reduce cost is to get the drain type that will work best for your issue. If you notice leaking mostly after rainfall, a footing drainage system probably won’t work as well for your problem as the much cheaper shallow French drain. Conversely, if you have severe leaking, paying once for the costly interior drainage system will probably prevent you from having to install an interior system later if you find that another option doesn’t fix the heavy leaking. Consult a professional.

Lastly, there are some things you can do to help prevent water from getting to your foundation, which in turn will reduce the load on your drainage system. Adequately grading your topsoil away from your foundation, installing gutters and downspouts properly, or adding a retaining wall for excessive surface water will help reduce the amount of water that is able to reach your drainage system and foundation walls, helping to prevent future leaking and the need for additional home improvement.

Check out the video below to learn about installing gutters: