Avoiding Costly Errors: Top 5 Mistakes Contractors Make When Installing Retaining Walls
Retaining walls play a crucial role in supporting soil and preventing erosion, making them a vital element in landscaping and construction projects. However, there can be mistakes made when installing a retaining wall potentially leading to structural issues and costly repairs down the line.
1. Inadequate Site Preparation: One of the most common errors is insufficient site preparation. Failing to assess soil conditions, drainage issues, and the overall topography can result in a poorly designed and unstable retaining wall. Contractors must conduct a thorough site analysis before starting any installation. This can include soil testing, evaluating groundwater levels, ensuring proper drainage to prevent water accumulation behind the wall, and planning the proper wall layout of the wall to retain the slope required.
Avoidance Tip: Invest time in a comprehensive site assessment, and collaborate with geotechnical engineers for walls above 4’, if needed. Proper grading, drainage solutions, and understanding soil characteristics are essential for a successful retaining wall installation.
2. Ignoring Proper Drainage: Inadequate drainage can lead to hydrostatic pressure behind the wall, causing retaining walls to buckle and move. Contractors often underestimate the importance of incorporating drainage features into the wall design. Without proper drainage, water can accumulate behind the wall, leading to erosion, soil instability, and potential structural damage.
Avoidance Tip: Include effective drainage solutions such as gravel backfill, weep holes, and drainage pipes in the wall design. Ensure that water is directed away from the wall to prevent excess pressure and soil saturation.
3. Incorrect Material Selection: Choosing the wrong materials for the retaining wall can compromise its structural integrity and longevity. Contractors may opt for materials that are not suitable for the specific site conditions, leading to issues like cracking, tilting, or bulging. Also, selecting the wrong size block for modular wall applications, may cause structural issues. Selecting the right size block for the applications is a key decision that needs to be made.
Avoidance Tip: Select materials based on the site's requirements, considering factors such as soil type, wall height, and aesthetic preferences. Consult with engineers or certified retaining wall specialists to determine the most appropriate materials for the project.
4. Neglecting Proper Compaction: Improper compaction of the soil behind and beneath the retaining wall is a common oversight. Inadequate compaction can result in settling and instability, affecting the overall performance of the wall. Soil settles when air pockets burst which makes the soil move. Not using compaction equipment or the right size equipment can lead to failure of the wall.
Avoidance Tip: Prioritize proper compaction techniques during construction. Use compaction equipment to achieve the required density of the soil behind and beneath the wall. Regular testing and inspection can help ensure that compaction meets the specified standards. Compacting in the proper lift heights and using the correct size equipment will allow for a successful installation.
5. Lack of Professional Engineering Involvement & Geogrid Use: Some contractors may bypass the expertise of professional engineers during the design and installation phases. Each township may vary on their requirements, but most commonly, walls above 4’ in height require an engineer to be involved. This oversight of having an engineer involved can lead to suboptimal designs, inadequate structural support, failure to include geogrid, and increased risks of failure. Neglecting geogrid does not stabilize the soil behind the wall and prevents the wall(s) from being tethered into the slope.
Avoidance Tip: Collaborate with experienced geotechnical and structural engineers to assess site conditions and develop a well-engineered retaining wall design. Professional input can help identify potential issues early on and ensure a durable and safe installation. Install the correct strength geogrid in the proper depth and number of lifts to properly stabilize the soil allowing for a strengthened wall system.
Avoiding these common mistakes is crucial for contractors looking to deliver successful and long-lasting retaining wall installations. By investing time in thorough site assessments, proper drainage solutions, material selection, compaction, and involving professional engineering expertise, contractors can mitigate risks and ensure the stability and functionality of retaining walls for years to come.
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