Leaning or cracked retaining walls: what should a homeowner do?
A leaning retaining wall, or one that is cracking or moving, should be assessed in the context of its ground levels, drainage, loads and construction. A photograph may show a symptom, but it cannot establish the cause or confirm whether the wall is safe.
This guide outlines sensible first steps for a homeowner or builder. It is not a diagnosis, repair design or emergency service.
Key points
- New movement, bulging, cracking or soil loss should not be ignored.
- Water, poor drainage, surcharge loading and loss of foundation support are common matters to investigate.
- Excavating beside a wall can remove support and make movement worse.
- Do not add a fence, pool, driveway or fill beside a wall without checking the additional load.
- An inspection should establish what is visible, what is uncertain and what further information is required.
Signs that warrant closer attention
Common warning signs include a wall face that has rotated or bulged, new or widening cracks, displaced posts or sleepers, soil appearing through joints, ponding behind the wall, blocked outlets, erosion at the toe, or a fence that has started to lean with the wall.
One sign does not establish the severity. The rate of change, wall type, retained height, nearby loads and the consequences of further movement all matter. Record the condition with dated photographs and note whether it changes after rainfall.
What can cause movement or damage?
| Possible factor | What may need checking |
|---|---|
| Water and drainage | Surface runoff, blocked outlets, seepage, erosion, saturated backfill and the discharge route. |
| Loading above | Driveways, vehicles, buildings, pools, stored materials, fences or new fill near the wall. |
| Ground and footing | Soft or uncontrolled fill, footing scour, loss of toe support, slope movement or reactive soil. |
| Construction changes | Excavation, altered levels, removed vegetation, a new adjoining wall or work on a neighbouring property. |
Several factors can act together. For example, a wall may tolerate a load in dry conditions but move after drainage is blocked or ground becomes saturated.
What to do first
Keep people and plant clear of an unstable area
If there is sudden movement, a large bulge, collapse or exposed footing, keep clear and avoid placing vehicles, materials or people above or below the affected area.
Do not excavate beside the wall
Excavation, removal of the toe or cutting into retained ground can reduce support. Temporary works should be planned before digging.
Record the site
Take wide and close photographs, measure visible cracks where practical, note recent rain and record nearby buildings, fences, pools, driveways and drainage outlets.
Arrange an appropriate inspection
An engineer can review the wall, site levels, drainage, loads and available records, then identify whether design, monitoring, temporary support or further testing is needed.
What an engineering inspection can cover
An inspection may consider the wall system, visible footing and drainage, retained and adjoining ground levels, nearby surcharge loads, signs of rotation or settlement, construction access and the likely failure mechanisms. It may also identify matters that cannot be confirmed without excavation, survey, soil testing or other investigation.
The outcome should distinguish observed facts from assumptions. Where the wall is close to a boundary, building, pool, service or another wall, those relationships should be included in the assessment.
Repair, replacement or monitoring
There is no single repair detail for every retaining wall. Depending on the condition and cause, a project may involve drainage work, removal of a load, local repair, strengthening, partial replacement, complete replacement or monitoring before a decision is made.
A repair that treats only the visible crack may not address water, footing movement or surcharge. The proposed work should be checked against the wall’s design, approvals and construction constraints before it starts.
Common questions
Can I tell if a retaining wall is dangerous from a photograph?
A photograph can help identify visible symptoms, but it cannot confirm stability or the cause. Site conditions and the wall’s movement need to be assessed.
Should I repair the crack straight away?
First establish whether the crack is cosmetic, active or associated with movement. Avoid covering evidence or excavating beside the wall before appropriate advice.
Can I build a fence on a leaning wall?
Do not add a fence or other load until the wall and its fixings have been checked. Wind and impact loads can affect the design.
What information should I send an engineer?
Provide the address, wall dimensions, photographs, nearby loads and structures, drainage details, recent changes and any drawings or approvals.
General information only
This guide is general information, not a safety assessment, engineering design or repair instruction. If there is active movement, collapse or risk to people or property, keep clear and obtain site-specific professional advice.
Concerned about a retaining wall?
Send us the property address, photographs, approximate wall dimensions and any available plans. We can advise what inspection, engineering or supporting site information is likely to be required.