When a retaining wall fails — leaning, cracking, or bulging — the natural assumption is that the wall itself was built poorly. In EMS Engineering Consultancy’s experience assessing retaining wall issues across Melbourne, the wall structure is rarely the actual root cause. Far more often, the real problem is what’s happening behind and beneath it: drainage.

• 25 August 2026
• Komal Chauhan

What a Retaining Wall Is Actually Resisting

A retaining wall isn’t just holding back soil — it’s resisting the combined pressure of soil, and critically, any water trapped within that soil. Saturated soil is significantly heavier and exerts far more lateral pressure than dry soil. A wall correctly engineered for typical soil loading can still fail if water is allowed to build up behind it, because the actual load it’s experiencing is well beyond what it was designed for.

This is why retaining wall design isn’t purely a structural calculation — it’s a combined structural and drainage problem, and treating it as one without the other is one of the most common reasons retaining walls fail prematurely.

Common Drainage Failures Behind Retaining Wall Problems

A few recurring issues show up repeatedly in retaining wall assessments:

• Missing or blocked agricultural drainage behind the wall, allowing water to accumulate rather than being carried away
• Inadequate or blocked weep holes, preventing built-up water pressure from being relieved
• Surface water directed toward the wall rather than away from it, often due to nearby landscaping or paving changes made after the wall was built
• Insufficient granular backfill, meaning the material directly behind the wall doesn’t drain effectively even if a drainage system exists

Why This Gets Missed So Often

Drainage is invisible once a retaining wall is backfilled and landscaped — by the time a problem becomes visible above ground, the underlying drainage issue may have been developing for a long period. This is part of why retaining wall assessments need to consider the full system, not just visible signs of movement, and why a wall that “looks fine” for years can develop problems after a period of unusually wet weather.

What Proper Retaining Wall Engineering Looks Like

A structural engineer designing or assessing a retaining wall typically considers:

• Soil type and classification for the specific site
• Wall height and the resulting lateral load
• A drainage strategy specific to the site — not a generic assumption
• Surface water management around the wall, not just behind it
• Appropriate materials and reinforcement for the loads involved

What to Do If You Suspect a Drainage-Related Problem

Signs like leaning, cracking, bulging, or water pooling near the base of a retaining wall are worth having assessed properly rather than patched cosmetically. A structural engineer can determine whether the issue is drainage-related, structural, or both — which matters significantly for how it should be fixed. Repairing visible cracking without addressing an underlying drainage problem typically means the same issue resurfaces.

For builders and developers planning new retaining structures, involving a structural engineer at the design stage — rather than treating drainage as a landscaping afterthought — is the most reliable way to avoid these problems altogether. EMS Engineering Consultancy designs retaining walls with drainage treated as a core part of the structural solution, not a separate consideration bolted on afterward.