Retaining Walls in Gungahlin

The town centre suburb

Wikipedia says Gungahlin is a suburb of Canberra that includes the Town Centre for the district of the same name, with the postcode 2912. The name comes from the homestead of the Crace family, who owned the land from 1877 until it was resumed by the Commonwealth. The article says it is one of the most densely populated suburbs in Canberra. Hibberson Street is the commercial heart, and the article lists two local clubs, a library and a senior high school.

What the census shows

The article says Gungahlin's population was 8,586 at the 2021 census, up from 5,617 in 2011. It reports that 35.5 per cent of dwellings were separate houses, 17.4 per cent were semi-detached, row or terrace houses or townhouses, and 46.5 per cent were flats or apartments. Retaining walls here are most often a feature of the separate houses and townhouses. If yours is a townhouse, ask who owns the wall. Tell each builder whether you are an owner or a tenant, because a request about a shared or unit-title wall usually goes to the owners corporation first.

Light rail and works nearby

Gungahlin Town Centre is one endpoint of stage 1 of the light rail network, which runs to Civic. A suburb with new transport and building work has plenty of contractors and plenty of scheduling. Ask each builder when they could start and whether the dates hold if the weather turns. Before You Dig Australia gives asset plans on request, and a busy area has many buried services, so ask who is requesting yours.

Shale and mudstone

The geology section says the suburb is underlain by the Silurian Canberra Formation, mostly slaty shale and mudstone, with bands of ashstone in the south and north-west. It says the Gungahlin Fault passes through the east of the town centre. Shale can break up and shed water in sheets after rain, so a wall on a cut slope needs drainage behind it. Yakka Labour gives $40 to $100 per linear metre for drainage and says it is where walls most often fail.

Fill, cut and approvals

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, and its development approval page treats cut-in and fill walls differently. A newly graded block in a dense suburb may have both. Ask a certifier which applies to yours, and check the licence on the Access Canberra register.

Where to start

For a long boundary wall, read our concrete sleeper guide. For a low garden terrace, read the timber guide.

What is Gungahlin built on?

Wikipedia says the suburb is underlain by the Silurian Canberra Formation, mostly slaty shale and mudstone. It is general information, not a site assessment.

What share of Gungahlin homes are separate houses?

Wikipedia gives 35.5 per cent separate houses, 17.4 per cent semi-detached or townhouses and 46.5 per cent flats or apartments in its demographics section.

Who requests the Before You Dig plans?

Ask each builder. Before You Dig Australia gives asset plans on request, and a quote should say who does it.