Sloping sites present a special challenge to homeowners. Pool areas, patios, garden sheds, play areas and other functions which require relatively level ground cannot be realised without changing the terrain. Steep sites are also difficult to access and mow; not to mention problems associated with slopes such as erosion and limited water retention capacity.
A common solution to a sloping site is using retaining walls. They hold back slopes and can be used to increase the usable space on your property. A good retaining wall is also a visual element that adds character to your garden. They introduce a third dimension to your landscape.
Retaining walls two feet or less in height are easy and usually safe to build without too much structural considerations. The trouble starts when you need taller retaining walls which support significant loads.
These must be treated as structural elements. It is recommended that you hire a civil engineer to help you design such walls. It is important to ensure that the foundation of the wall is stable and structurally sound. It should extend at least one foot beyond the front and the back of the base width of the wall.
Drainage is also an important consideration. Many retaining walls fail because of pressure due to water or excess soil moisture that builds up behind them.
To avert this, retaining wall should provide some means by which this water can freely drain down and away from the wall. This can be accomplished by having a gravel backfill and drain pipes or ‘weep’ holes to allow water to drain from behind the wall.
There are many materials that can be used to construct retaining walls. The most common ones include natural stone, precast concrete blocks, poured concrete and even timber.
Natural stones make for the most aesthetically appealing retaining wall materials. You have a wide variety of choices to fit just about any architectural or garden style.
Precast concrete gravity blocks are also becoming faster and easier to assemble. Modern concrete blocks are simply stalked on top of one another and then secured in place with pins, clips or interlocking edges. Poured concrete on the other hand are mostly applied in complex commercial projects or where structural considerations are paramount.
The writer is a landscape architect
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