Underpinning in Sydney

What underpinning in Sydney actually involves

The NSW Government defines underpinning as building a new support structure under a wall, column or footings without removing the superstructure, to prevent collapse from excessive settlement or another failure, or to let the loads on a building increase. CSIRO names the usual reasons a footing loses its ground: clay swelling and shrinking, erosion, saturation, tree roots and leaking pipes. A household sees step cracks through the mortar beds and floors that turn bouncy.

Digging beside a footing

The dig carries risk. CSIRO says excavation around footings must be properly engineered, because removing soil within the angle of repose will cause subsidence. Welsh Government guidance, outside NSW, describes the usual method as excavating short sections under the footing one at a time and filling them with concrete, and warns that voids can remain against the old footing. It says a trial hole beside the footings, assessed by an engineer or surveyor, is generally the first step: ask any provider what they will dig first, and who reads it.

There is no single Sydney rule for the dig. The councils we read attach requirements to particular mapped land: landslide risk on the Northern Beaches and in The Hills, acid sulfate soils in Bayside and Inner West, the flood planning area in Penrith. The dig can also reach next door: where a consent involves excavation below the base of a neighbour's footings, the state's Regulation makes it a condition that the consent holder protect and support the neighbouring building at their own expense, and underpin it if necessary, unless they own that land or its owner agrees in writing to the condition not applying.

Underpinning in Sydney — common questions

Do I need a licensed contractor for underpinning?

Yes, above A$5,000. Ask any provider for a licence number and the categories it covers.

Does underpinning need council approval?

It depends on the job, the land and the council, and no source we read says underpinning as such does or does not need a development application.

How much does underpinning cost?

This site sets no price. The costs page shows only the bands two independent businesses each publish.