Retaining walls are a staple for stabilizing slopes and controlling elevation changes around Sydney properties. Over time though, many retaining walls start developing an outward lean or bulge. This creates an unsightly appearance and poses serious structural issues if the leaning continues unchecked. But what actually causes a previously straight retaining wall to start shifting out of alignment? As experienced building inspectors in Sydney, Local Property Inspections looks at the common underlying reasons.
Insufficient Foundations
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One of the most frequent causes of retaining wall leaning is inadequate foundations underneath. Walls need proper reinforced footings that extend below frost level and bear onto firm, compacted ground. If foundations are too shallow or rest on poorly compacted fill, segments of the wall can sink and tilt outwards. The weight of the wall and soil pressure behind pushes sunken areas forward.
Poor Drainage
When water builds up behind retaining walls, it creates enormous hydrostatic pressure. Even small volumes generate tons of lateral force pressing against the wall. Inadequate drainage, such as no gravel backfill, weep holes or drainage pipes, allows excessive water saturation. Over time, the wall literally gets pushed forward by the drainage issues behind it.
Over-Steepened Slopes
Retaining walls are designed to withstand a certain amount of soil pressure from the slope they retain. When the slope behind the wall is steeper than specifications, the lateral earth pressure can exceed the wall’s load capacity. This slowly forces the top of the wall outward as the slope pushes against it. Regrading the slope is often needed.
Erosion and Undermining
Flowing stormwater or drainage issues that create erosion along a wall’s base is also problematic. As soil gets washed away from the foundation, sections of the wall get undermined and begin separating. This enables water to penetrate cracks and further destabilize the wall’s supports. Ongoing erosion necessitates rebuilding.
Tree Root Damage
Trees growing near retaining walls can cause damage, either from roots traversing under the wall or trunk/branch growth pressing on the face. As expanding roots lift and crack foundations, wall sections tilt forward. Likewise, outward tree growth leverages walls outward. Removing Problem trees is recommended.
Soil Issues
Retaining walls are vulnerable when the soil composition behind them changes significantly over time. Heavy new fill dumped behind the wall or washed out fine particles creates voids and compaction differences that lead to subsidence and spot failures. Homogenous and well-compacted soil is vital.
Vehicle Vibrations
Contrary to intuition, the vibrations from heavy vehicles on nearby roads can disturb retaining walls. Constant vibrations loosen soil behind the wall and weaken mortar joints in masonry over the years. The wall slowly settles out of alignment and requires reinforcing.
Overall Deterioration
Like any structure, retaining walls deteriorate as years pass. Harsh weather, cyclical freezing and thawing, vegetation growth, and ageing materials take a toll. Eroded mortar joints, cracked bricks and corroded steel eventually lead to localized subsidence and outward leaning.
Seeking Expert Advice
If your retaining wall starts developing a lean, don’t ignore it and hope the problem goes away. Contact qualified engineers like Local Property Inspections to assess the underlying factors causing the wall to shift. They can provide recommendations on suitable repair options to re-stabilize your leaning wall. Act before the problem worsens.
Conclusion
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A multitude of issues can cause previously level retaining walls to start slanting forward over time. Seeking professional inspections early on is key to determine the root causes so appropriate repairs can be made. With the right expertise, leaning retaining walls can be remedied successfully.