The signs of retaining wall failure can be obvious such as cracking, bulging, or bowing, however other symptoms can be more subtle or seem unrelated unless you know what to look for, like poor drainage.
If you’re worried that your retaining wall might fail and live in the Gold Coast, Brisbane, or Northern Rivers area, contact us today.
JHA Australia is a Forensic and Structural Engineering company actively consulting and providing reports for the analysis, refurbishment and repair of a variety of structures Australia-wide. Our Engineers can determine the cause, extent, and methodology of repair and certify any repair work.
What is a retaining wall?
There are four main types of retaining wall:
- Gravity retaining walls
- Anchored retaining walls
- Sheet pile retaining walls
- Cantilever retaining walls
Each type of retaining wall has different applications; the right one for you can depend on many circumstances. We can provide advice on the best kind of wall for your circumstances, so contact us today for advice.
Signs of retaining wall failure
Bowing or cracking of the retaining wall
If your retaining wall starts to bend, bow, crack, tilt, bulge, buckle, or just not look like it should, then there’s a good chance it’s on its way to failure.
To prevent total failure, you can retrofit reinforcements to strengthen it, such as extending the footing or adding extra concrete to the base. There are also other options, such as anchors for additional strength.
Poor drainage
If you’ve noticed that the area surrounding your retaining wall has stopped draining water as well as it did, you may have a problem. If your drainage system backs up, it’s essential to try and remedy the situation as fast as you can, as water build-up can be a death sentence for a retaining wall.
Subsidence of surrounding areas
Subsidence refers to the sinking of soil in the area surrounding a structure, and subsidence near your retaining wall is a bad sign. The soil displacement could be applying excessive pressure to the wall and can be an indication that it’s about to fail.
Causes of retaining wall failure
Unanticipated loads
When installing your retaining wall, be sure to accurately estimate the total load it will have to withstand, as an incorrect estimation can lead to premature failure. If you build a retaining wall for a patch of land on which you’re going to park your car but fail to mention this during construction, the load-bearing capacity of the wall will be off, and it may fail sooner than expected.
Poor drainage
Not only is noticeably poorer drainage of the area surrounding your retaining wall a sign of failure, but poor drainage is also a cause of failure. Wet soil is far heavier than dry soil, so implementing and maintaining a functional drainage system is vital for the longevity of your retaining wall.
Issues with the foundations
Like most structures, a good retaining wall is only as good as its foundations. Therefore, you must ensure to properly compact the soil on which the wall will be sitting and provide adequate footing for the weight of the earth in question.
Sub-par handiwork
Unfortunately, sub-par handiwork is a fact in every industry and is a common cause of failure with retaining walls.
Age
Age gets us all in the end. If a retaining wall is getting towards its twilight years, eventually, it will fail. So long as it was installed correctly, however, you should be able to get many years of use out of it – in fact, there is a retaining wall surrounding a tomb in Ireland that has been standing for more than 5,000 years!
When do you need a retaining wall?
According to the Building Act 1975 (s75), if soil conditions, ground levels, excavation or filling make it necessary to protect land, buildings or structures, then a retaining wall or other reasonable method must be constructed to prevent soil movement. When creating this retaining wall, adequate drainage of the land, buildings, or structure must be factored in.
Do I need a permit to build a retaining wall?
According to the Gold Coast City Council:
“Retaining walls need building approval unless they meet all the following criteria:
- less than 1.0 metre high
- further than 1.5 metres to a building or another retaining wall
- only support the soil behind the wall, nothing above
- not part of a pool fencing
- combined wall and fence height are less than 2.0 metres
- not built over a service (sewer or stormwater)
- meets structural requirements
- not in an easement or covenant area
- meets earlier development conditions
- not in a waterfront setback area.”
Be sure to check your local council’s requirements, as they vary greatly from region to region.
Need help evaluating the causes of your retaining wall failure?
At JHA Australia, we have over 30 years of experience in Forensic and Structural engineering. We are fully licensed and insured and pride ourselves on producing quality and cost-effective reporting. Our experience extends across Australia, completing numerous residential, commercial, governmental and industrial building projects.
If you suspect your retaining wall is failing, we can evaluate the structure and establish the causes of failure, as well as provide certification if the structure is deemed safe and stable. We can also provide forms 12 and 15 if you plan to construct a new retaining wall.
So if you need help identifying any signs or causes of failure or need certification as part of the building approval process for your retaining wall, then contact us today.