A French drain is an effective way to deal with water issues in a basement. Installing a French drain involves digging a trench, lining it with gravel, and installing a perforated pipe to carry water away from the basement. Once the French drain system is installed, an important next step is properly covering it to allow it to function effectively.
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Why is it important to cover a French drain?
Covering a French drain is crucial for several reasons:
- Protects the drain – A cover prevents dirt, debris and other material from clogging the perforated pipe or packed gravel. This helps maintain proper water flow.
- Prevents erosion – Covers prevent soil or gravel from washing into the drain trench over time. This maintains the integrity of the drain.
- Allows for proper drainage – Covers permit water to seep into the drain while blocking loose material. This optimizes drainage performance.
- Aesthetic value – Covers provide a finished look to the French drain installation.
An improperly covered or exposed French drain is prone to clogging and other issues that can render it ineffective. Taking steps to properly cover a basement French drain is crucial.
How to Cover a French Drain in a Basement
Here are the key steps involved in covering a basement French drain:
1. Inspect the drain trench
Before covering, thoroughly inspect the drain trench to ensure proper installation. Check that:
- The trench is dug to the correct depth, with proper slope for drainage.
- Gravel is filled evenly throughout the trench, surrounding the perforated pipe.
- The pipe is laid evenly along the trench bottom.
- Pipe perforations face down to allow water inlet.
- Pipe joints and connections are properly fitted.
- An outlet is in place to direct water away from foundation.
Rectify any issues before moving on to covering the drain.
2. Install a filter fabric
Line the top of the drain trench with a filter fabric. This acts as a barrier to prevent soil and sediment from washing into the gravel drain bed. The fabric should cover the gravel completely.
3. Backfill partially with gravel
Pour a 1-2 inch layer of gravel over the filter fabric, extending over the edges of the trench. This covers and protects the fabric during subsequent installation steps.
4. Install a protective covering
Next, install a protective covering over the gravel layer. Some options include:
- Plastic sheeting – Durable 4-6 mil plastic sheeting acts as an affordable protective barrier.
- Geotextile drainage matting – Special matting provides excellent protection while remaining permeable to water flow.
- Concrete splash blocks – Preformed blocks create a barrier and transition water flow out of downspouts.
Covering the entire trench with one of these options provides an effective protective layer.
5. Backfill with remaining gravel
Cover the protective layer with the remaining gravel, filling the trench completely level with the basement floor. Pack down gravel lightly with a tamping tool.
6. Install surface layer
Finally, install a top surface layer over the gravel based on your floor plans:
- Bare concrete – Leave drainage gravel exposed for industrial basement look.
- Concrete – Pour a level concrete floor over the gravel up to grade.
- Pavers – Install interlocking pavers over a bedding sand layer.
- Flooring – Install laminate, LVP or other floating floor over underlayment.
Choose an attractive, functional finished surface. Be sure to slope surfaces away from foundation walls to direct water to the drain.
Key Covering Materials
Some of the key materials commonly used for covering basement French drains include:
Plastic Sheeting
- Very affordable protective covering.
- Polyethylene or PVC sheets 4-6 mils thick.
- Withstands pressure and soil movement.
- Impermeable to debris while permitting water flow.
- Install over gravel layer to hold other covers in place.
Geotextile Fabric Matting
- Specialized woven or non-woven drainage matting.
- Allows water passage while blocking sediment.
- Heavy-duty materials resist punctures and damage.
- More expensive, but longer-lasting than plastic sheeting.
- Equally effective for French drain protection.
Concrete Splash Blocks
- Preformed solid concrete pieces.
- Place below downspout outlets to prevent erosion.
- Direct gutter water flow out of drain tiles.
- Durable, decorative enhancement to finishes.
- Cost-effective outdoor surface protection.
While plastic sheeting is the cheapest option, materials like geotextile matting provide the best long-term French drain covering. Concrete splash blocks help protect the outdoor drain outlet.
Covering Tips and Tricks
Some helpful tips for properly covering basement French drains include:
- Inspect drain directions so covers permit proper water flow.
- Overlap plastic sheeting edges and seams at least 12 inches.
- Extend cover layers over trench edges to prevent cave-ins.
- Anchor covers in place with gravel and drainage matting.
- Avoid puncturing protective covers during installation.
- Always use filter fabric to prevent soil and sediment intrusion.
Taking measures to prevent cover damage and maintain proper drainage slope is key. A durable, impermeable covering that directs water into the drain trench is ideal.
Costs for French Drain Covers
Here are some typical costs for materials used for covering French drains:
| Cover Material | Cost per Square Foot |
|---|---|
| Plastic sheeting | $0.10 – $0.25 |
| Geotextile matting | $0.75 – $1.25 |
| Concrete splash blocks | $2 – $4 each |
Plastic sheeting provides an economical covering solution at around $0.15 per square foot. Higher-quality geotextile matting costs about $1 more per square foot but offers advanced drainage capabilities and strength. Pre-cast splash blocks cost around $2 to $4 each based on dimensions.
Overall costs for French drain covers in a 10×3 foot basement trench could total:
- Plastic sheeting – Around $45
- Geotextile fabric – Around $90
- Splash blocks – $20 – $40
Labor to properly install these cover materials will also add to the project costs.
Conclusion
Covering a basement French drain is an important process that ensures proper functioning. First, the drain trench installation must be inspected. Filter fabric is laid to prevent sediment intrusion. A protective cover of plastic sheeting, geotextile matting, or splash blocks is installed over the gravel bed. The trench is backfilled before installing a finished floor. Covering materials range from inexpensive plastic sheeting at $0.15 per square foot to higher-end drainage matting at around $1 per square foot. With proper covering techniques, a French drain can effectively keep basements dry for many years.