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About Retaining Walls
What is a retaining wall
A retaining wall is a structure built to hold back a slope or increase the stability of a slope in landscaping.
It's purpose is to prevent lateral movement (movement downhill) of an embankment or slope in a landscape area.
There are two types of retaining walls:
Solid face/pitch (enclosed)
concrete, brick, mortared stone. Never build a brick wall higher than 10 courses without an engineer's certificate. Check your council requirements -
drainage behind wall is critical.
less stable.
more prone to collapsing, more pressure on wall face from behind.
bigger footing needed.
Dry packed (free draining)
crib walls, sleeper walls, dry packed stone and rock boulder walls. -
more stable.
must have a batter.
solid footing necessary.
drainage is usually included in wall design
Batter
Is the angle at which the wall is constructed. Some walls require little, if any batter. This depends on the material the wall is built out of, the strength of its construction and also the height of the wall.
On average a wall could be built on a batter of between 1:10 and 1:20
Selection of wall
Consider the points when choosing the style of wall you are going to build and the material to be used.
- cost of materials
- size of job
- what the wall has to hold back, type of soil, building, fence etc
- aesthetics
- height of wall
- customer requirements
Walls built out of brick, block, sandstone or even good bush rock tend to be more expensive and time consuming, they require better drainage, bigger footings and sometimes an engineer's approval depending on the height. Check in the planning and approvals section of this website.
A large solid face wall such as these should not be attempted without the essential skills and experience.
Timber walls are cheaper on a whole. Some treated timbers are a bit more expensive but they last longer the untreated timber. Whilst drainage is necessary, the cost is a lot less then rock etc.
Risk situations for retaining walls
Risk of a slip can be reduced by cutting back the original slope and backfilling with a free draining material.
An extra terrace will give added strength and support at the base of the slope without any cutting.