When planning a retaining wall in Auckland, selecting the right design and material is crucial for longevity, functionality, and aesthetic appeal. Auckland's unique climate and soil conditions require careful consideration to ensure the retaining wall not only serves its purpose but also withstands the local environmental factors. Here, we explore five design principles for retaining walls in Auckland.
Tip #1 - Check your ground conditions and location.
The type of soil on your property affects how well a retaining wall will hold up over time.
Clay Soil: Most of Auckland sites on Clay soils which retains moisture and expands when wet, this can exert pressure on the retaining wall. Materials like timber, keystone, or other gravity walls are suitable as they provide robust structural support.
Sandy Soil: East and North Auckland can see some sandy soil conditions which drains quickly but lacks cohesion, potentially causing erosion around the wall base. Concrete block retaining walls or driven pile walls are typically recommended for sandy soils due to their stability and ability to resist erosion. Rock / Basalt: A large part of central Auckland is situated on basalt rock and lava flows. This can prove difficult to excavate through and nearly impossible to drill through, due to this retaining walls with shallow foundations are preferable. Concrete block or keystones are favoured here.
Tip #2 - Just like raw chicken, an undercooked design is no good.
Think with a long term vision when designing your retaining wall, we see many retaining walls that have failed and require our expertise to repair them. They are often under-designed, not built for the conditions and with a small amount of extra work (larger poles, better drainage etc) done 5 or 10 years ago when they were first built they would still be standing today.
"The most common cause of failure is not the wall type or the construction of the wall, it's the design and the safety factors." – Jeff, Engineer.
Tip #3 - You've remembered the retaining wall, don't forget the drainage.
In general, drainage plays an important part in the performance of the wall, high rainfall can lead to saturated soil conditions, affecting stability. The key to good retaining wall design is to get the surface and ground water away to the drainage network as fast as possible.
Areas with poor drainage, such as clay soils or low-lying areas prone to water accumulation, require materials that resist water penetration and can handle hydrostatic pressure. Reinforced Concrete or retaining walls with proper drainage systems are suitable.
Tip #4 - How steep is your slope?
The steepness and stability of the slope where the retaining wall will be installed impact the material choice. A wall will need to be designed to handle any extra pressure or commonly referred to as "surcharge" a slope is adding.
Still have questions?
Don't worry, we have answers! We will manage the entire Auckland Council Building Consent process including the design, we engage a team of consultants that we regularly work with so you get the optimum result.
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