Soil, slabs and movement in Rockbank VIC

The City of Melton is documented as Newer Volcanics basalt of the Western Volcanic Plains, and where residual basaltic clay is present that ground is reactive, shrinking and swelling as moisture changes. We have not verified the mapping for Rockbank specifically, so we make no claim about what sits under any particular block. What we can say is what goes wrong when a slab as built departs from what was designed, and severe cracking measured between 4mm and 10mm is what that looks like at the far end.

The City of Melton sits on Newer Volcanics basalt of the Western Volcanic Plains.

Where residual basaltic clay is present, it shrinks and swells with moisture.

We have not verified the mapping for Rockbank specifically and make no claim about it.

Cracking is categorised by width. Between 4mm and 10mm is severe.

Only your own soil report classifies your lot under AS 2870.

More about Rockbank

Written by our local inspection team from work carried out in Rockbank. Licensed building practitioners.

Guides for Rockbank owners and buyers

10 March 2026 · 6 min read

Strap bracing that was never tensioned

Fitted, visible, and contributing nothing.

7 April 2026 · 6 min read

Vapour barrier faults on a slab near Rockbank

Not extended, and punctures left open.

12 May 2026 · 7 min read

Booking stage inspections around Rockbank

Where the windows sit in a Melton corridor program.

Soil, slabs and movement in Rockbank VIC: common questions

What site classification does Rockbank have?

There is no suburb-wide answer, and we will not invent one. Classification is determined lot by lot from an individual soil report. Ask your builder for yours and check the slab was designed to it.

Is the ground reactive here?

The City of Melton is documented as Newer Volcanics basalt, and residual basaltic clay is reactive. We have not verified the mapping for Rockbank specifically, so treat that as corridor context rather than a statement about your block.

How bad is severe cracking?

Cracks between 4mm and 10mm sit in the severe range under the tolerances guide, well outside acceptable, and they warrant an engineering opinion rather than filling.