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How to fix a retaining wall that is coming away and turning to dust.
Hello @Richard44
It looks like your retaining wall is suffering from a combination of structural separation and surface deterioration, most likely caused by moisture ingress, salt attack, and age-related concrete decay. The “dusting” and the white, crumbly surface you see are signs of efflorescence (salt deposits) and spalling (breakdown of the concrete surface due to water and chemical action). Here are some suggestions on how you can approach repairing the retaining wall.
First, address the cause of moisture. Retaining walls often deteriorate because water collects behind them or seeps through cracks, dissolving salts in the concrete and carrying them to the surface. Check that the wall has proper drainage. There should be gravel and weep holes at the base on the soil side. If these are missing or blocked, install or clear them to allow trapped water to escape. Improving drainage will stop the ongoing damage before you attempt repairs.
Second, remove all loose and crumbling material. Use a stiff wire brush or masonry chisel to clean away the friable, dusty surface down to solid concrete. If you find large cracks or hollow areas, widen them slightly with a cold chisel so you can fill them properly narrow cracks can trap repair compounds and prevent a solid bond. After brushing, rinse lightly and let the surface dry.
Third, apply a masonry repair mortar such as Sika 20kg Sika MonoTop-352NFG Structural Repair Mortar. For deeper cracks or sections that have separated, the same product can be used. Fill cracks completely, smooth the surface, and let it cure according to the manufacturer’s instructions.
If the wall has significant movement or large separation from its base, this may indicate soil pressure or foundation issues. In that case, it would be wise to have a structural engineer assess whether reinforcement or partial rebuilding is needed.
Please remember to wear personal protection such as gloves, goggles and a mask when working on your project.
If you need further assistance, please let us know.
Eric
