The national average cost of French drain installation is $25-$50 per linear foot. Your total cost will depend on how many feet of pipes you need to lay, and whether you're installing your drainage system in an easy to access location, or somewhere more difficult—like between your foundation and basement. Your total typically covers materials and the labor cost for installation.
French drain installation, which can take place on the interior or exterior of your home, is a good solution for homeowners at risk of water problems, like flooding or heavy rain.
Like most plumbing, installation of a French drain and pipes is a project best left for a professional French drain installation contractor. Before you hire a pro to help, get an estimate of your installation and French drain costs.
What's in this cost guide?
- What is a French drain?
- French drain cost factors
- French drain installation steps
- How to hire a drainage contractor
What is a French drain?
A French drain—sometimes called a perimeter drain, a rock drain, a weeping tile, an agricultural drain, or a curtain drain—is a rainwater or water runoff management system that helps homes avoid flooding and water damage. French drains protect the home or property by absorbing and redirecting excess water away from (or out of) the building, through pipes, and into appropriate channels such as city sewer mains.
Interior French drains can be installed inside of a home (such as in the basement floor), around the side of a home or building or behind an outdoor retaining wall as a solution for poor drainage, heavy rain, and other wet conditions that could damage your home. French drains are useful behind exterior retaining walls to prevent drainage from your pipes from pooling and damaging a wall's structural integrity over time.
Depending on the grade a house is sitting on, French drains are pipes installed between a hill or slope and the house. French drains prevent surface water runoff from the hill from putting excess water strain on the house. While French drains are not a method of waterproofing, they are a method of water detouring—taking water from one location and putting it elsewhere via the drain's pipes to prevent water damage or other water problems.
Because installing a French drain often involves excavation, construction, and plumbing, it's typically handled by a general contractor.
What impacts French drain installation costs?
Contractors often charge by the linear foot for French drain installation and the national average cost is $25-$50 per square foot. Material and installation costs for a French drainage system depend on the amount of labor required, materials, and how accessible the site is. Several factors that impact installation costs include:
- Trenches: The cost to dig a trench will impact your total. If workers have to hand dig the trenches, the job will take longer and the cost per linear foot will be higher than if they can drive a mini-excavator right to the site for the trench-digging process.
- Accessibility of the site. The average cost of installation is $25 per linear square foot for easy to access sites and $50 per linear square foot for sites that require additional work to excavate.
- Soil content. If your soil has shale or other conditions that make it hard to dig, that can increase work time and overall project costs.
Here are some examples of cost per linear foot for French drain installation from a Thumbtack pro and drainage contractor in Michigan:
- Base rate for outdoor French drain installation: $25 per linear foot
- Basement French drain installation: $45 per square foot
How are french drains installed?
The installation process for French drains will depend on whether you're installing them indoors or outdoors. For example, the drains that a Thumbtack pro in Michigan installs are a multilayer filtration system buried approximately 24 inches in the ground.
To install them, they excavate a trench (or trenches) to absorb and redirect water. Generally, the drains are installed in a line below and directly horizontal to the water source (such as a hill or slope). French drains can also run along a house or other site for protection from water. As water comes down the hill or slope, it will gather in the parallel-laying drain, run through the pipes and then discharge out both sides of the drain—neatly avoiding the house.
To dig a trench for a French drain, the contractors lay a tubular drainage system wrapped in a geotextile or landscape fabric, which is water-permeable, inside the house. There are clean stones for water to travel through inside the geotextile fabric, as well as a perforated pipe at the bottom, which absorbs any water coming through the multilayer filtration system. The drains are then covered back up so they are not visible above ground—no pipes poking out of your yard.
Installing French drains in a basement requires cutting into the concrete to lay the drains next to (not above) the footing of the house foundation. Contractors cut the perimeter, butt the French drains against the foundation wall and run them to end in the home's sump pump. The sump pump then does its job of getting the excess water out.
French drains work well in wet basements or those prone to flooding, as well as basements with a porous foundation. While a French drain doesn't drain water from a basement, it allows the homeowner to control it.
How to hire a drainage contractor
Before you hire a general or drainage contractor to start digging up gravel and laying pipes, be sure to let them know about the physical accessibility of the project location to get an accurate estimate on your French drain costs. For example:
- Can they drive their equipment right to the location? Or will they need to carry items in by hand?
- Does the French drain need to be installed outdoors, in a basement, or in a crawl space?
- Are there underground utility lines nearby?
- What's the condition of your soil?
Hard-to-reach sites often cost more than easily accessible job sites. Once you discuss the details of your project, a service provider will be able to come up with a cost estimate for you.
If you're ready to install a French drain system in your home or yard, find a drainage specialist near you on Thumbtack.