Project Summary
- Overall Duration: 16 hours
- Proficiency Level: Novice
- Projected Expense: $8 to $10 for every 10 linear feet.
Various kinds of French drains exist, particularly those utilized in landscaping to manage surplus surface water. For instance, if your neighbor’s property is situated at a higher level than yours, heavy rainfall may cause water to flow onto your land. Since altering your neighbor’s terrain is not an option, improving your yard’s drainage is essential to handle the excess water. A French drain is a widely used and cost-effective remedy for this issue.
Contents
What is a French drain system?
A French drain used in landscaping consists of a trench filled with gravel and covered with landscaping fabric to prevent soil and silt from contaminating the gravel. Although certain variations of these drains incorporate a perforated drain pipe (often referred to as drain tile) and can be topped with grass, the classic French drain is more straightforward, lacking a drain pipe and featuring gravel that extends to the surface.
A French drain allows surface water to enter a trench filled with gravel, facilitating its movement. The trench is designed with a slight slope at the bottom, enabling gravity to direct the water toward an outlet at the trench’s end. At this outlet, the water can either be directed into a large swale, a dry well, or allowed to flow into an appropriate drainage zone or a rain garden.
Legislation and Guidelines
Yard drainage initiatives may be subject to limitations imposed by local construction regulations, zoning ordinances, or community guidelines. It is essential to verify your plans with the local building and zoning authorities, as well as the homeowners association, if relevant. Diverting water runoff from your property into stormwater systems may be prohibited. If your proposal is not sanctioned, consider implementing an alternative drainage solution, like a dry well, to retain the drainage water on your property, allowing it to percolate into the soil instead of flowing across the surface.
Requirements
Devices / Instruments
- Hammer
- Mason’s boundary
- Line stage
- Measuring tape
- Quadrate shovel
- Excavation spade
- Box cutter
- Garden rake
Materials
- Timber posts
- Garden fabric
- Garden fabric anchors
- Granite that has been ground into small pieces.
Instructions
Instructions
Identify a Site for the Trench
Evaluate the sections of your yard that are susceptible to flooding to identify a suitable position and pathway for your French drain. It is crucial to establish the direction for the water to flow and to ensure that the drainage outlet is appropriately situated. Additionally, think about the implications of having a visible gravel channel in your yard: How could it influence pathways, sightlines, or areas designated for leisure activities?
Obtain Authorization
Ensure that the drainage system in your yard does not negatively affect neighboring properties or public spaces, as this could result in legal issues. Verify with your local building authority that your plans comply with municipal regulations. Contact 8-1-1, the national Call Before You Dig hotline, to have all underground utility lines on your property identified. This step is crucial prior to any excavation work.
Examine the Incline
To effectively direct water to its intended location, a French drain should be installed with a slope. A slope of at least 1 percent is advisable, which translates to a 1-foot drop for every 100 feet of length. If your yard has a naturally steeper slope, that’s acceptable, but keep in mind that a steeper incline can increase water speed and potentially cause greater erosion at the discharge point. To assess the natural slope, drive a stake at both the start and end of the intended trench. Secure a mason’s line to one stake and extend it to the other, tying it off loosely. Attach a line level to the line, then detach the loose end, pull it tight, level it, and secure it to the stake. Measure the distance from the line to the ground at intervals of about 4 feet to observe the slope’s variation. You can modify the trench’s depth to achieve the desired slope, but working against a natural incline will require more excavation.
Excavate the Ditch
Adjust the stakes and level the line if needed, ensuring it runs through the center of the intended trench. Start the trench by slicing a straight line through the grass, 3 inches (or your preferred measurement) to one side of the line, using a square garden spade. Repeat the process on the opposite side, also 3 inches from the line, resulting in a trench width of 6 inches (or your preferred measurement). Remove the grass, then excavate the trench, ensuring the sides are vertical and the bottom is smooth and sloped. Frequently measure from the line to monitor the trench bottom’s slope, keeping in mind that you’re measuring into the trench, not to the surface. Dig the trench to your desired depth. For instance, a trench that is 50 feet long could be 8 to 10 inches deep at the starting point and 14 to 16 inches deep at the end (assuming the natural slope is fairly level). As you work, compact and smooth the trench bottom.
Cover the trench with fabric.
Cover the trench with landscape fabric, aiming to use a single, continuous piece if feasible. If that’s not possible, ensure that the fabric pieces overlap by a minimum of 12 inches, and fasten the ends with fabric staples hammered into the ground. Make sure to secure the fabric at both ends with staples. Leave extra fabric on both sides of the trench, which you can trim to the appropriate length later.
Tip
The landscape fabric should be arranged to overlap in the direction of the intended water flow. The fabric positioned on the higher side of the trench must be placed over the fabric on the lower side.
Fill the Ditch
Fill the trench with coarse drainage gravel, like crushed granite, ensuring it is level with the adjacent ground or sod. Use a rake to smooth the gravel, making it even with the trench’s top. As an alternative, you can slightly overfill the trench and create a mound of gravel, with the highest point in the center, to enhance the trench’s visibility. Use a utility knife to trim any excess landscape fabric along the trench’s edges.
When to Seek Professional Assistance
If you notice that excess surface water is pooling or flowing near your home, or if it causes seasonal flooding indoors, it’s advisable to consult a professional. Similarly, if your intended trench path directs water closer to your home or disrupts natural drainage patterns, expert guidance is essential. Poorly designed drainage solutions can lead to more issues than they resolve. In cases of severe drainage challenges, you may need to regrade extensive sections of your property, which necessitates engineering expertise and heavy machinery.
What exactly is a French drain?
A French drain consists of a trench lined with landscape fabric and filled with gravel, designed to channel surface water effectively. Its primary purpose is to prevent water accumulation and to redirect water away from the foundations of homes and other buildings.
What is the required depth for a French drain?
French drains typically range from 8 inches to 2 feet in depth. This depth can be modified along the length of the drain to establish a slope.
