Retaining walls are more than decorative landscaping features. They perform an important structural job by holding back soil, controlling changes in elevation and helping create usable areas on sloped properties.
Because retaining walls constantly resist pressure from soil and water, problems can develop when drainage, construction, foundation support or surrounding ground conditions are inadequate.
A small crack may initially appear harmless. Over time, however, homeowners may notice that the wall begins leaning forward, bulging outward, separating at joints or shifting at the base.
These symptoms should not automatically be treated as cosmetic damage.
Understanding why retaining walls fail is essential because repairing the visible crack without correcting the underlying cause can allow the same problem to return.
What Does a Retaining Wall Actually Do?
A retaining wall holds back soil that would otherwise naturally move downhill.
Depending on the property, retaining walls may be used to:
- Support sloped yards
- Create level patios
- Protect driveways
- Form garden terraces
- Support walkways
- Control soil near foundations
- Manage elevation changes
- Reduce erosion
- Create usable outdoor space
The wall must resist the pressure created by the soil behind it.
When that soil becomes saturated with water, the pressure can increase significantly.
This is why drainage is one of the most important considerations in retaining-wall construction and repair.
1. Poor Drainage Behind the Wall
One of the most common reasons retaining walls lean, crack or bulge is water collecting behind them.
Rain enters the soil above and behind the wall.
If that water cannot escape, the soil becomes saturated and heavier.
The trapped water also creates hydrostatic pressure against the wall.
Instead of resisting only dry soil, the wall must now withstand the combined pressure of soil and water.
Over time, this can push the wall outward.
Warning signs associated with poor drainage include:
- Water emerging through mortar joints
- Constantly wet sections of wall
- White mineral deposits
- Soil remaining saturated above the wall
- Bulging masonry
- Horizontal cracking
- Wall movement after heavy rainfall
Drainage should therefore be one of the first things evaluated when a retaining wall begins moving.
2. Missing or Inadequate Drainage Systems
A properly designed retaining wall often includes drainage components behind the structure.
Depending on the wall, these may include:
- Clean drainage stone
- Perforated pipe
- Filter fabric
- Weep holes
- Gravel backfill
- Surface grading
- A suitable discharge location
These components allow water to move away instead of becoming trapped behind the wall.
Problems occur when drainage was never installed, was undersized or becomes blocked.
For example, fine soil can gradually migrate into drainage stone if appropriate filter fabric was not used.
A perforated pipe can also become clogged or damaged.
Even a well-built wall may eventually experience excessive pressure if its drainage system stops working properly.
3. Incorrect Grading Above the Wall
The ground surrounding a retaining wall plays an important role in determining where rainwater goes.
If the land above the wall slopes toward it, large amounts of surface runoff may reach the soil directly behind the structure.
Water from:
- Roof downspouts
- Driveways
- Patios
- Walkways
- Neighboring slopes
- Lawn drainage
can also increase the amount of moisture behind the wall.
A retaining wall drainage solution should therefore consider the surrounding property, not just the wall itself.
Redirecting surface water may substantially reduce the amount of pressure the wall must handle.
4. An Inadequate Foundation or Base
Retaining walls need stable support underneath them.
If the base is too shallow, poorly compacted or unsuitable for the wall size, movement can develop.
The bottom of the wall may begin shifting while the upper portion remains under pressure from the soil.
Homeowners may notice:
- Tilting
- Uneven settlement
- Cracks near the base
- Sections separating
- Wall caps becoming uneven
The quality of the base becomes increasingly important as retaining-wall height increases.
A small decorative landscape wall and a large structural retaining wall do not experience the same loads and should not necessarily be constructed in the same way.
5. Soil Settlement
Soil does not always remain perfectly stable.
Newly disturbed soil can settle over time, particularly if it was not properly compacted.
Settlement may create voids beneath portions of the wall.
Different areas may then move at different rates.
This uneven movement can result in:
- Stair-step cracking
- Vertical cracks
- Separated blocks
- Uneven wall caps
- Localized leaning
Repairing the crack without stabilizing the affected section may not provide a lasting solution.
6. Frost Heave and Freeze-Thaw Conditions
Cold winters can create additional pressure on outdoor masonry.
Moist soil can freeze and expand.
This movement can push against retaining walls and foundations.
Repeated freeze-thaw cycles may gradually contribute to:
- Wall displacement
- Cracked mortar
- Loose stones
- Shifted blocks
- Base movement
Drainage becomes especially important in cold climates because reducing excess moisture around the wall can also reduce some freeze-related pressure.
7. Excessive Soil Pressure
Every retaining wall is designed to resist a certain amount of pressure.
Problems can arise when conditions behind the wall change after construction.
For example, homeowners may later add:
- A driveway
- Heavy landscaping
- Large planters
- A patio
- A shed
- Additional soil
- Vehicle parking
These additions can increase the load near the wall.
This extra load is sometimes called a surcharge.
A wall originally designed only to retain soil may not have been intended to support heavy loads positioned immediately behind it.
If substantial changes have been made above a retaining wall, they should be considered when movement develops.
8. Tree Roots
Trees and large shrubs can affect retaining walls in several ways.
As roots grow, they may push against:
- Masonry
- Wall foundations
- Drainage pipes
- Pavers
- Surrounding soil
Roots can also alter soil moisture conditions.
Large trees close to a retaining wall may therefore contribute to movement in certain circumstances.
That does not mean every nearby tree needs to be removed.
Instead, root growth should be considered as one possible factor when investigating unexplained wall movement.
9. Erosion Around the Wall
Water can damage a retaining wall even when it does not collect directly behind it.
Fast-moving surface water may wash soil away near:
- The ends of the wall
- The bottom of the wall
- Drainage outlets
- Steps
- Adjacent slopes
As supporting soil disappears, sections of the wall can lose stability.
Homeowners may notice exposed footing areas, channels in the soil or gaps beneath masonry.
Controlling erosion is therefore another important part of retaining-wall maintenance.
10. Deteriorating Mortar
Brick and stone retaining walls often rely on mortar joints.
Over time, mortar may deteriorate because of:
- Age
- Moisture
- Freeze-thaw cycles
- Salt exposure
- Poor drainage
- Previous improper repairs
Small areas of mortar deterioration can often be repaired.
However, missing mortar throughout large portions of a retaining wall may reduce stability and allow additional water into the structure.
Homeowners dealing with damaged stone, brick, block or concrete walls can review professional masonry and hardscape repair services to understand how retaining-wall repairs may involve repointing, unit replacement, rebuilding and drainage correction.
Why Do Retaining Walls Lean?
Leaning usually indicates that forces behind the wall are gradually overcoming its ability to resist them.
Common causes include:
- Excessive water pressure
- Poor base construction
- Soil movement
- Frost movement
- Inadequate wall design
- Excessive loads above the wall
A slight lean does not necessarily mean immediate collapse.
However, movement should be monitored because a wall that continues leaning is unlikely to correct itself.
The cause should be determined before simply attempting to push or rebuild the visible section.
Why Do Retaining Walls Bulge?
Bulging often occurs when a portion of the wall is being pushed outward more strongly than surrounding areas.
Water pressure is a common contributor.
For masonry retaining walls, deteriorated mortar or movement within internal sections can also produce localized bulging.
Signs include:
- A rounded outward section
- Misaligned stones or bricks
- Opening mortar joints
- Cracks surrounding the bulge
- Loose wall caps
Bulging deserves attention because it may indicate that the wall is losing its original alignment.
Why Do Retaining Walls Crack?
Cracks can develop for many reasons.
Small mortar cracks may result from normal weathering.
More significant cracks may indicate:
- Settlement
- Lateral pressure
- Base movement
- Frost action
- Excessive loading
- Drainage failure
The pattern matters.
A small isolated mortar crack is different from a large crack extending through several blocks or stones.
Likewise, cracking combined with leaning or displacement generally deserves more attention than a stable surface crack.
When Can a Retaining Wall Be Repaired?
Not every damaged retaining wall needs complete replacement.
Localized repair may be possible when:
- The wall remains generally straight
- Damage affects only a small section
- Most masonry units remain sound
- Mortar failure is limited
- Drainage problems can be corrected
- The base remains stable
Repairs may include:
- Repointing
- Replacing damaged brick or block
- Resetting stone
- Replacing wall caps
- Repairing localized cracks
- Improving drainage
- Correcting nearby grading
The best repair addresses both the visible deterioration and whatever caused it.
When Might Rebuilding Be Necessary?
More extensive rebuilding may be appropriate when:
- The wall is significantly leaning
- Large areas are bulging
- Several sections have shifted
- The base has failed
- Masonry units are extensively deteriorated
- Previous repairs repeatedly fail
- Large structural cracks are present
- Drainage failure has caused widespread movement
Sometimes only part of the wall needs reconstruction.
Other situations may require replacement of a larger section.
The condition of the wall should determine the scope rather than assuming every crack requires complete rebuilding.
How French Drains Can Help Retaining Walls
Drainage systems are often installed behind or near retaining walls to control groundwater and surface runoff.
A typical system may include a perforated drainage pipe surrounded by stone and protected with filter fabric.
Water enters the drainage zone and is carried toward an appropriate outlet.
Homeowners experiencing water accumulation behind retaining walls can learn more about French drains and exterior drainage systems used around retaining walls, foundations, patios and other hardscape areas.
The discharge location is important.
Collecting water serves little purpose if it is released somewhere that creates another drainage problem.
What Are Weep Holes?
Weep holes are openings that allow trapped water to escape through a retaining wall.
They can be useful in certain masonry wall designs.
If weep holes become blocked, water may accumulate behind the wall.
Homeowners should avoid sealing drainage openings simply because water is visible coming through them.
The water may be demonstrating that the drainage feature is performing its intended function.
Drainage Should Be Considered Before Rebuilding
Imagine a retaining wall that is leaning because water repeatedly accumulates behind it.
The wall is demolished and rebuilt using new masonry.
But the drainage conditions remain unchanged.
Rain continues saturating the soil.
Pressure begins building again.
Eventually, the replacement wall may develop similar problems.
This illustrates why rebuilding alone is not always enough.
The project should consider:
- Water source
- Surface grading
- Backfill
- Drainage stone
- Drain pipe
- Wall foundation
- Discharge location
A retaining wall is most likely to perform well when structural support and drainage work together.
Warning Signs Homeowners Should Not Ignore
Homeowners should periodically inspect retaining walls, especially after winter or periods of heavy rainfall.
Watch for:
- Increasing lean
- Bulging
- New cracks
- Opening joints
- Loose stones
- Shifted blocks
- Soil washing through the wall
- Standing water above the wall
- Blocked drainage outlets
- Uneven wall caps
- Settlement at the base
- Movement around nearby patios or walkways
Photographs can be useful for comparing changes over time.
If a crack or lean becomes noticeably worse, professional evaluation is advisable.
Do Not Ignore the Area Around the Wall
Retaining-wall problems often involve more than the wall itself.
During an inspection, consider:
Above the wall
Where does rainwater come from?
Behind the wall
Can groundwater escape?
At the bottom
Is erosion removing supporting soil?
Beside the wall
Are the ends properly supported?
Nearby hardscaping
Are patios or driveways directing water toward it?
Looking at these areas together provides a better understanding of why the wall may be failing.
Preventing Future Retaining-Wall Problems
Routine observation and drainage maintenance can reduce the risk of major deterioration.
Homeowners should:
- Keep drainage outlets clear.
- Prevent excessive runoff from being directed behind the wall.
- Maintain gutters and downspouts nearby.
- Monitor cracks and movement.
- Repair deteriorated mortar early.
- Watch for erosion.
- Avoid major loading changes without considering the wall.
- Correct persistent standing water.
- Inspect walls after severe winters.
- Address leaning before movement becomes extensive.
Small maintenance measures can help protect a retaining wall for many years.
Final Thoughts
Retaining walls rarely lean, crack or bulge without a reason.
Water pressure, poor drainage, soil movement, inadequate base preparation, frost conditions, erosion and excessive loading can all contribute to deterioration.
The visible damage may only be the symptom.
A lasting repair requires understanding what is happening behind, below and around the wall.
For property owners who need retaining-wall, masonry and drainage conditions evaluated together, Optane Masonry and Home Improvements provides masonry, hardscaping and exterior drainage services across New York and New Jersey.
Whether a retaining wall needs repointing, localized repair, drainage improvements, partial rebuilding or complete reconstruction depends on its actual condition.
Addressing the problem early gives homeowners more repair options and reduces the risk that a relatively small issue develops into widespread wall failure.
