Understanding Retaining Wall Drainage
Retaining wall drainage is crucial to ensure the wall’s longevity and stability. Proper drainage helps prevent water buildup behind the wall. The result of too much water can be intense hydrostatic pressure which can cause it to fail – with catastrophic consequences.
Retaining Wall Drain Pipe Installation
Drainage System Components
Regardless of whether you have a natural stone retaining wall or a concrete block retaining wall, you must consider these components as part of your overall strategy in order to mitigate the effects of water pressure on your retaining wall.
A Drainage System Should be Installed on the Upslope Side of Retaining Wall Tiers to Avoid Putting too Much Pressure on the Retaining Wall and Potentially Causing a Wall Failure
French Drains
A French drain system is an effective drainage solution for redirecting surface and groundwater away from your retaining wall. It is an extremely effective drainage solution and should be included as part of the retaining wall design.
The system typically consists of a trench lined with landscape fabric and filled with gravel or rock. On top of this resides a perforated pipe that redirects water away from the problem area. The pipe is covered with a mesh sock that only lets water in and keeps dirt and debris out in order to prevent the pipe from clogging.
The trench is dug at a slight angle to ensure proper water flow downhill and away from your retaining wall. Your yard must be properly graded with an appropriate slope to allow for proper water flow. When water enters the trench, it seeps through the gravel and into the perforated pipe. The pipe then channels the water to a designated drainage area, such as a storm drain, dry well, or a lower-lying part of the property where it can safely disperse.
Weep Holes
Weep holes are small openings strategically placed in structures to allow for the drainage of water and moisture. Commonly found in brick walls, retaining walls, and even window sills! Weep holes aren’t part of a french drain system – however they are an additional method to prevent water buildup behind your retaining wall.
These holes play a crucial role in preventing water accumulation and subsequent damage. They allow any water that has penetrated the wall to escape, thereby preventing water buildup that could lead to mold, mildew, and structural damage. By facilitating proper drainage, weep holes help maintain the integrity and longevity of the structure.
The effectiveness of weep holes depends largely on their proper placement and maintenance. They must be kept clear of debris and obstructions to function correctly. You should use screens or other devices to prevent insects and pests from entering while still allowing water to escape.
Foundation Drains
Foundation drains are vital for directing water away from the wall base. Installed at the lowest point, they prevent water accumulation by allowing it to flow out.
Backfill Materials
Choosing the right backfill material is essential for efficient drainage and supporting the wall’s structural integrity. Granular backfill materials like gravel or crushed stone allow better water flow compared to clay or other fine materials. This minimizes water retention and reduces hydrostatic pressure behind the wall.
Proper backfill material should be compacted in layers during construction to provide stability and reduce settling. This ensures the wall remains structurally sound and durable over time. By carefully selecting and using backfill materials, the overall drainage system becomes more effective, reducing potential damage and increasing the wall’s longevity.
Drainage Outlet
A drainage outlet should be installed at the end of the drain pipe. The outlet helps water flow freely away from the wall, preventing water damage and erosion issues. Outlet needs to direct water away from structures and neighboring properties to avoid causing damage.
Your French Drain Must Exit to an Area Where the Water Can be Safely Deposited Where it Won’t Cause Damage to Property
Construction Considerations
Construction Best Practices
Following best practices during construction is essential. Firstly, the trench for the drain pipe should be at least 18 inches to two feet deep. The pipe should slope away from the wall at a rate of 1 inch per 8 feet to ensure proper water flow. After placing the drain pipe, it should be covered with crushed stone.
Compaction is another critical step. Using a compactor helps ensure that the fill material is tightly packed. This improves stability and prevents settling. It’s also important to place the drainage fabric correctly and make sure that there are no folds or wrinkles. This ensures efficient water flow and reduces the chance of potential problems like waterlogging or structural failure. Regular inspection can also help identify and address any issues early on.
Surface Drainage and Landscaping Solutions
Surface drainage is crucial for the effectiveness of block retaining walls. Proper surface drainage prevents water from pooling at the wall base, which can lead to erosion and instability.
Landscaping plays a critical role. It enhances both the functionality and the aesthetic appeal of the wall. The right landscaping elements can help to absorb water, channel water, and prevent erosion. Proper landscaping elements can actually enhance the effectiveness of your drainage system.
- Plant Selection: Integrate plants that have strong root systems. This helps in erosion control and maintains soil structure.
- Mulching: Apply mulch to reduce water runoff and to keep the soil moist.
- Terracing: Build terraces to slow down water flow and provide planting areas.
- Swales: Construct shallow ditches to direct surface water away.
- Rock Gardens: Use rocks to break up water flow and add visual interest.
Incorporating hardscaping solutions like pathways and patios can also aid in surface drainage. These elements can be designed to direct water flow efficiently while adding to the landscape’s beauty.
Maintaining Your Drainage System
Maintaining a French drain system is essential to ensure it continues to function effectively in managing water drainage.
French Drain Maintenance
French drains tend to work well without much intervention, but periodic inspections and maintenance can help you avoid more serious problems such as wall failure down the road.
- Regular Inspections: Periodically check the visible components of the French drain system, such as the ends of the drain pipe and any surface grates. Look for signs of blockages, standing water, or erosion around the drain area.
- Clear Debris: Remove any debris, leaves, or sediment that may have accumulated around the drain openings. This can be done using a garden rake or a small shovel. Keeping the area around the drain clear ensures that water can easily enter the system.
- Flush the System: To clean the interior of the French drain, you can use a garden hose to flush water through the pipe. Insert the hose at one end of the drain and let the water run for several minutes. This helps to dislodge and remove any sediment or debris that may have built up inside the perforated pipe.
- Check for Clogs: If you notice that water is not draining properly, there may be a clog within the pipe. Use a plumber’s snake or a high-pressure water jet to clear any blockages. Insert the snake or water jet into the pipe and work it through to break up and remove the obstruction.
- Maintain Surrounding Area: Ensure that the landscape fabric and gravel around the trench remain intact and free from soil contamination. Over time, soil can infiltrate the gravel and clog the system, so it’s important to maintain the integrity of the materials used in the French drain.
- Bring in a Pro: If you encounter persistent issues or are unsure about the condition of your French drain, consider hiring a professional to conduct a thorough inspection and maintenance. Professionals have specialized tools and expertise to diagnose and resolve more complex problems.
Weep Hole Maintenance
Weep holes are more likely to run into issues than french drains – especially if they aren’t properly protected from debris and intruders like rodents and insects.
- Eye Test: Begin by visually inspecting the weep holes for any obvious signs of blockage or damage. Look for debris, dirt, or plant growth that may be obstructing the holes. Examine the areas around the weep holes for signs of moisture damage, such as mold, mildew, or efflorescence (a white, powdery deposit). These signs can indicate that the weep holes are not functioning properly.
- Water Flow Analysis: During or after a rainstorm, observe whether water is exiting through the weep holes. Lack of water flow during wet conditions can indicate a blockage that needs attention.
- Probe the Weep Hole: Gently insert a small probe, such as a piece of wire or a screwdriver, into the weep holes to check for obstructions. Be careful not to damage the structure or the weep hole itself.
- Clear Blockages: If you find any debris or obstructions in the weep holes, carefully remove them using a small brush, wire, or compressed air. Ensure the holes are clear to allow for proper drainage.
- Keep it Clean: Keep the area around the weep holes free from dirt, leaves, and other debris that could potentially block the openings. Regularly sweeping or washing the area can help prevent blockages.
- Install Screens or Covers: Consider installing screens or covers over the weep holes to prevent insects and larger debris from entering while still allowing water to escape. These can be purchased at hardware stores and are easy to install. Ideally this should be done as part of the retaining wall construction process.
- Repair Damaged Weep Holes: If you notice any damage to the weep holes, such as cracks or deterioration, repair them promptly. This may involve patching the masonry or replacing damaged materials to ensure the weep holes function correctly.
