Retaining Walls in Casey

A new suburb on a slope

Wikipedia says Casey is a suburb of north-west Gungahlin, about 4 kilometres from the Gungahlin Town Centre and about 13 kilometres from the centre of Canberra. It is bound by Horse Park Drive and Clarrie Hermes Drive and takes its name from Richard Casey, the 16th Governor-General of Australia. Settlement began in 2010, after construction work on roads and other infrastructure started in September 2008. That makes Casey one of the newer parts of Canberra, so many homes here are recent.

The fall of the land

The geology section says the landscape slopes to the south east, with a line of hills forming a ridge on the north-west side as a backdrop. It gives the low point as 622 metres at the roundabout joining Gungahlin Drive, Horse Park Drive and Clarrie Hermes Drive, and the highest point as 726 metres in the north-west corner. That is a rise of 104 metres across the suburb, and it explains why walls and terraces are common on blocks that follow the slope.

Land that was once a rural property

The history section says that until 1990 Casey was part of the former Gold Creek property, a rural holding of 3,940 acres with Gold Creek Homestead at its centre. It says the flat, even ground in parts of the suburb suited horse racing, and that a stand of trees along Horse Park Drive marks the original alignment of the Queanbeyan-Yass Road. A graded new-suburb block usually has fill on some parts. Ask each builder whether a wall is cut, fill or both.

Stormwater already built in

The development section says stormwater infrastructure, including a sediment pond, was completed during early construction. A new suburb has its stormwater routes designed in, so a wall's drainage outlet needs to reach a legal discharge point. Yakka Labour describes an outlet to a stormwater point or a safe discharge area. Ask a builder where yours will go, and who is responsible for any connection.

Low walls and the rules

ACT Planning says a retaining wall does not need a building approval if it is not higher than 1.2 metres from the top of the wall to the lowest adjacent ground level. Its development approval page gives 0.4 metres as the limit for fill walls and cut-in walls within 1.5 metres of a side or rear boundary. A terrace stepped down a slope can stay low, but each step still has to be checked.

Where to start

For a low garden terrace, read our timber wall guide. For a long boundary wall on a graded block, read the concrete sleeper guide. Before You Dig Australia gives asset plans on request, so ask who will request them. Then send the form with your street, the length, the height and what sits above and below the wall.

Does Casey slope enough to need retaining walls?

Wikipedia gives a low point of 622 metres and a highest point of 726 metres in Casey, with the land sloping to the south east. Your block may differ, so measure it.

Was Casey once a farm?

Wikipedia says it was part of the Gold Creek rural property until 1990. We cannot say what that means for a particular block.

Where does the water from a retaining wall go in a new suburb?

Yakka Labour describes an outlet to stormwater or a safe discharge area. Ask each builder where yours will go and who arranges any connection.