Underpinning in Bridgeman Downs
Bridgeman Downs is the one suburb on this site where, in our samples, Queensland's geological survey maps a hard weathered land surface: two of five points come back as a duricrust of ferricrete, silcrete and indurated palaeosols, and the other three as the Petrie Formation. Council's creek and waterway flood planning area covers a modest part of the suburb.
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Underpinning around Bridgeman Downs
The survey describes the duricrust as an old land surface at the top of a deep weathering profile on Petrie Formation basalt. The Petrie Formation is itself listed as mudstone, siltstone, sandstone, oil shale, brown coal and limestone, and it is the only named formation our samples found here. The survey does not say how thick the hard surface is at any one block.
A hard cap over weathered rock is a fact about the map, not a finding about a footing, and CSIRO says soil classification generally comes from a geotechnical report. The creek and waterway flood planning area is the overlay mapping we found over the suburb, though over much less of it than in Bald Hills or Coopers Plains. When a subsidence complaint is made, QBCC's inspectors check leaking taps, air conditioning lines discharging next to footings, and blocked gutters and downpipes; the same checks are where a diagnosis here starts.
Permits and Brisbane City Council rules
Council classes digging directly related to underpinning as building work, and lists underpinning works below an existing building as its own example. Its page adds that overlays can change the planning-approval allowance, so the creek flood mapping is worth a look on City Plan online before a certifier is asked what approval the job needs.
Source: Brisbane City Council, Filling and excavation guideline (May 2026) and Filling and excavation page; City Plan 2014 creek and waterway flood planning area mapping, last modified 23 September 2025. — confirm current requirements with Brisbane City Council.
Our Bridgeman Downs service area
A Bridgeman Downs enquiry is referred on to an independent provider, who gets in touch to look at the house.
See all Underpinning in Brisbane. We also work in Bald Hills, where flood planning mapping covers a large part of the suburb.
Call (07) 3523 1792Last reviewed · Updated · First published