Retaining walls
Rock and boulder walls
Heavy quarry rock and boulders, placed by machine to hold a level change. Built as a structure and drained like one, not stacked as a garden feature.
How a rock wall holds ground
A rock wall holds ground with the mass and the interlock of the rock itself rather than with posts and panels. Done properly that means rock sized for the height being retained, seated back into the batter with the right lean, and drained behind exactly as a sleeper wall is drained. Without that, it is rock resting against a slope, and the slope wins.
Rock is where most of the confusion sits, because the same material is used for a garden feature and for a structure and the two look similar from the front. We build them as retaining structures, on the same sites and under the same contract as the engineered walls, which is why they usually appear alongside one rather than instead of one.
Where the wall retains enough ground to need a design, it is built from a stamped design to AS 4678, the Australian Standard for earth retaining structures, which sets out how the load on a wall is calculated and how it has to be drained. Registered building practitioner CDB U 58737, so the permit pathway and the contract sit with the same business that places the rock.
What it solves
- A level change that suits mass, not panelsWhere there is room to batter back, rock holds the ground without a line of posts and a footing under every one.
- Ground the rock has to come out of anywayOn a rock site the material broken out of the cut can go back into the face, which takes cartage out of the job.
- A finish that is not a grey panelWhere the wall is the first thing seen from the street, rock reads as landform rather than as structure.
- Frontages and access roadsLarge boulders at a frontage, as at Croydon, where the wall doubles as edge protection for a truck route.
Examples of the work
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Built as a wallRock sized for the height retained, seated back into the batter rather than tipped against it. -
The size we handleQuarry rock at this size is placed by machine and seated individually. -
Alongside the engineered wallRock and sleeper on the same site, under the same contract, meeting where the levels change. -
The ground it holdsFrom above the fall is obvious in a way no specification conveys.
- Registered builderCDB U 58737
- Built to AS 4678Earth retaining structures
- Quarry sourcedRock sized to the retained height
- Machine placedSeated individually, not tipped
Send the fall and the access
Rock walls need room to batter back and access for the machine that places the rock. Those two things decide whether rock is the right answer for your site or whether a structural wall suits it better.