A properly installed French drain around a foundation can manage excess water and safeguard your property against water-related damage. However, some mistakes with any installation can be costly, so homeowners should be aware of them. In this blog post, you will discover the nine common French drain mistakes and how to avoid them.
HD Foundations is your trusted foundation specialist serving the entire DFW metroplex. Our team has extensive experience designing French drains that work best for your home.
Not Calling Utility Companies
One of the most common French drain mistakes is failing to call utility companies beforehand. When building trenching projects, it is vital to determine where utility lines are located before you start doing any digging on your property. People need to remember this very crucial detail. Digging a trench through your home’s gas, sewage, water, or power lines can be dangerous. Any damage to these utility lines will be costly to repair.
In some cities, homeowners may be mandated to contact various utility companies before excavation can be performed. Failing to do so can result in fines and penalties. Before proceeding with your project, it is best to check with local homeowner associations and regional authorities.
Contacting utility companies allows them to mark the locations of underground utilities. These organizations will send out their staff to paint or mark the exact locations of their utility lines, allowing you to plan your French drain installation more efficiently, avoiding potential conflicts with existing lines underground.
Furthermore, utility companies can provide the necessary guidance on how to proceed with trenching. They can also suggest alternative drainage solutions and methods to work around installed utility lines.
Failing to Line the Trench with Drainage Fabric
Next on our list of French drain mistakes is failing to line the trench with a drainage fabric. This fabric should be made of non-woven geotextile, which can separate the soil to prevent debris and dirt from mixing with the rock filling. This layer of material allows the water to flow freely along your trench.
Aside from soil separation, this layer of drainage fabric also serves other functions:
- Filter Function: It acts as a filter to prevent the accumulation of silt, debris, and organic matter within the drain.
- Weed Prevention: The fabric helps prevent weed and plant roots from growing into the drain, which is especially helpful if you’re building a French drain located in a garden or landscaped area.
- Erosion Control: A drainage fabric layer can also help prevent erosion by stabilizing the soil around the French drain. This feature can help preserve the integrity of the drain and the surrounding landscape.
Many contractors recommend using a non-woven geotextile fabric. It should weigh 4 oz to 6 oz, which is the type that tends to last for decades.
Returning the Excavated Soil Into the Trench
Installing a French drain around a foundation is a labor-intensive process, so some think it is better to put the excavated soil back instead of transferring it to another area. However, doing so is a terrible mistake. Remember that a French drain became necessary because the ground wasn’t draining properly. Returning the non-porous soil you removed can cause the drain system to clog over time.
In addition, the excavated soil is typically loose and can be easily compacted. Placing it back into the trench and compacting it can reduce the permeability of the ground, making it less effective at allowing water to flow through. This can undermine the purpose of the French drain, which is designed to facilitate water drainage.
Using Gravel Alone Minus the Drain Pipe
The gravel on your trench by themselves cannot handle heavy water flow. A French drain requires this pipe for several crucial reasons:
- Efficient Water Collection: The drain pipe serves as the conduit for collecting and channeling water away from the problem area, which is usually a home’s foundation. Without a pipe, the rainwater would rely solely on seeping through the surrounding soil and gravel, which can be slower and less effective, especially during heavy rains.
- Faster Water Removal: A drain pipe accelerates water removal from the drainage area, providing a direct path for water to flow. In addition, the pipe prevents surface water from pooling and causing damage to your home’s foundation.
- Control Water Direction: With a drain pipe in place, you have more control over where the water is collected and discharged. Depending on your needs and local regulations, you can direct it to a suitable outlet, such as a stormwater system, a drainage ditch, or a dry well.
The most common drain pipe in many French drain systems is a 4″ or 6″ perforated pipe. This pipe is then covered with round drain rock, which allows the drainage system to move this water away from your home’s structure.
Incorrect Drain Rock Type
Using the correct type of drain rock for your system ensures proper drainage and better permeability. Many contractors will recommend using clean, natural round stones to allow water to flow better through the aggregate.
Ideally, you should use 1-1/2″ clean round-washed rock, which provides the best drainage. Further, you should avoid using pea gravel, which is usually smaller and creates slower flow rates. Aside from pea gravel, homeowners should also avoid using crushed rock, which has the tendency to clog pipe inlets.
If round rocks aren’t available in your location and the best option you have is crushed stone, you should use a different type of drain pipe. In this scenario, it is recommended to use a sock-wrapped drain pipe instead, which can prevent the fine particles of crushed stone from clogging the inlet holes in the slotted pipe.
Using the Wrong Landscape Fabric
There are different types of landscaping fabric you can obtain from suppliers. However, not all are best suited for constructing a French drain. The following are the recommended fabrics to ensure a functional and long-lasting French drainage system:
- Woven Geotextiles: These fabrics are made by weaving synthetic fibers together to create a durable, porous material. They are excellent for soil separation and filtration.
- Non-Woven Geotextiles: This type of fabric, on the other hand, is made by bonding or needle-punching synthetic fibers together. French drains often use them to prevent soil infiltration while still allowing water to flow through.
- Drainage Fabrics: Some fabrics are designed explicitly for drainage applications and are highly permeable. They are engineered to promote efficient water flow while preventing soil intrusion, making them an excellent choice for French drainage systems.
- Filter Fabric: Filter fabric is a general term encompassing various fabrics used for filtration systems. It is essential to select filter fabric designed explicitly for drainage applications and provides good permeability.
Many contractors use four to six-ounce weight non-woven drainage fabric for French drains. They have great flow-through rates and are pretty durable, often lasting as long as the usable life of a French drain. However, if you’re looking for better erosion control, many contractors recommend ultra-thick rip-rap fabric, the ones that are 8 oz and up. As a caveat, it is best to consult with your contractor if this fabric works well with your French drain’s design.
No Positive Drain Slope
The drain pipe must be set at an angle to allow water to drain properly. There are several scenarios that you should be aware of:
- Positive Slope: The ideal slope for a trench near a foundation is greater than 1% grade. At this angle, the canal can allow water to drain away efficiently from the inlet. A positive slope ensures that gravity can naturally distribute rainwater to the drain lines.
- Completely Flat Pipe: Zero slope pipes will not allow water to drain correctly, which causes pooling in the system.
- Low Spots: Water pooling can occur in low spots in the drain line, which can attract tree roots. When roots enter the drain, they can block water flow and reduce the effectiveness of your French drainage system.
- Negative Slope: Negative sloped pipes are less common but can still occur if the trench isn’t designed correctly. A negative slope makes it impossible to get any water flow.
A poorly designed trench will make your French drain less effective at drawing water away from your home’s foundation. Seasoned foundation experts from HD Foundations ensure that your channel is properly sloped so water is directed away from your infrastructure.
Placing the French Drain Beneath a Downspout without a Catch Basin
Gutter downspouts can be placed directly over a French drainage system or in-ground drain field. However, when creating this type of system, it is crucial to place a catch basin to better manage the sudden gush of rainwater, especially during a storm.
During heavy rains, gutters collect a lot of water, which can overwhelm and flood any drainage field. If this is the type of French drainage system you prefer, installing a catch basin before the drainage is best. After that, you can tie the drain to the basin for better rainwater management.
The catch basin also helps you capture leaves and other debris that get washed out of your gutters. This way, you prevent debris from entering your drainage system and clogging your drain lines.
Misdirected Pipe Holes
French drainage pipes are designed to be perforated, allowing the collected water to filter through. These perforations help to draw the water away from your home and direct the flow to a different place where it can be dispersed.
Positioning the holes in the piping sideways may seem logical since water can come from the sides. However, the most efficient position is when the perforations are pointed downwards, which provides the most efficient drainage possible with the help of gravity.
Work with Seasoned Professionals to Avoid Costly Design Mistakes
Avoiding these common mistakes ensures your French drain effectively redirects excess water. At HD Foundations, our certified professionals plan French drainage systems carefully, choosing suitable materials and using industry best practices. Schedule a free foundation repair estimate if you need a well-designed drainage system best suited for your home.