Line the Trench with Filter Fabric To keep the French drain free of dirt, silt and tree roots, lay water-permeable filter fabric or a weed barrier over the gravel bedding in the trench. Leave the filter fabric open with at least 10 inches of excess fabric at the sides.
Yes the trench should be lined with fabric. A fabric lined trench is better than a sock because larger surface area means it will take longer to clog.
But which gravel is ideal for a French drain? Hard rocks like washed river rock or granite chips are the ideal gravel for French drains. The gravel pieces should ideally average at least 1′′ wide to provide the best permeability for water to run along.
Non-woven geotextile fabric is the best choice for drainage applications where water flow through (permeability) is the main concern. Non-woven landscape fabric is commonly used in French-drains, drain-fields, and erosion control.
Line the Drain With Membrane to Minimise Blockage
Once your French drain is installed, maintenance is essential. Don't let it get blocked or you could end up with a moat around your building: great if you're looking to protect it from invaders – and not so great if you're trying to fight damp.
It is not absolutely necessary to use perforated pipe to create a French Drain.
Permits Needed to Install a French Drain
Generally, a small French drain on your property that doesn't change the flow of runoff entering and exiting your yard won't need a permit. Major projects that warrant your French drain to discharge into a municipal sewer or roadside ditch, however, do require one.
Pour and compact about 3 inches of gravel or landscaping stone along the bottom of the trench. This will act as bedding for the drainage piping.
Swales: A Natural Solution
They're a great option if you're looking for a more natural, eco-friendly alternative to French drains. A swale is typically lined with grass or vegetation that helps slow down and absorb water.
We use a non-woven double punched geotextile fabric that's designed to leech water away from your system. We always try to educate our clients and tell them, “Look, you don't want to use landscape fabric. Landscape fabric does not drain.
French drain depth: About 8 inches to 2 feet deep should be sufficient for many water-diverting projects, though related systems, such as those built around foundations and sub-ground living spaces, as well as the bases of retaining walls, may be deeper.
A French drain is a great solution for a wet basement or below-grade space, but, just like any other type of drain, French drains are susceptible to clogging. Soil and debris tend to build up inside the pipes, eventually stopping water from flowing.
A French drain needs to be surrounded by gravel in order to filter out silt and prevent clogging the drain pipe.
Installing a French drain costs $500 to $18,000, with a national average of $9,250. On average, you can expect to pay $10 to $100 per linear foot, or between $500 and $5,000 to have a 50-foot French drain installed.
Clay soil has poor permeability, meaning it doesn't allow water to pass through easily. In such cases, the effectiveness of a French drain may be limited as the water may struggle to drain away from the area efficiently. French drains may not be suitable for areas with high water tables.
Interior French drains are meant for waterproofing the basement or draining your crawl space. They cost more because contractors must tear out the basement floor (most often made of concrete), install the drain, and then repair it.
French drains are best suited for properties with moderate to severe water drainage issues, particularly in areas with heavy rain or poor soil drainage.
A French drain installation is widely recommended to utilize a 4-inch perforated pipe according to industry standards, the velocity requirements of the water flow, and the potential connections for downspouts.
The ideal distance for a French drain from the house ranges from 5 to 10 feet. This distance provides an adequate buffer to keep water from seeping into and around the foundation, which can be a common cause of damage.
A properly designed French drain system does not require an outlet. The water will simply soak into the soil as it flows along the perforated pipe. In fact, a French drain doesn't require an inlet on just one end either. You can construct the drain to accept water along its length, and disperse it underground.
Connect with local French drain experts to help with your project. Installing a French drain yourself is possible but labor-intensive and time-consuming. Call 811 a week or two before you start your project to get your buried utility lines marked.
You'll likely need a permit since this project may require soil grading to avoid drainage issues. Repairing your floor may be more cost-efficient than replacing it if grading is necessary. No permit may be required to hang drywall on exposed wooden wall studs in your garage.
French drain installation is a service offered by a diverse range of professionals from landscapers to plumbers to foundation specialists. These professionals bring a varied skill set to the project, often integrating the drainage system seamlessly with other landscaping or construction work.