Screw Piles in Sydney

What screw piles in Sydney actually involves

The published sources are papers on piles for buildings generally. They say a screw pile is installed by rotation from a drive head on a hydraulic excavator, and that its strength is often limited by the helix plate yielding before the ground does. So the first question is what governs this pile's capacity, the plate or the ground.

Four questions to ask

Second, how is each pile checked? A paper presented at an Australia New Zealand geomechanics conference says it is not appropriate for contractors to target a minimum measured torque as the sole means of verification, because torque reflects the soil the helix has already passed through, not the soil below it. Third, what set the founding levels? The same paper says a site investigation, preferably by cone penetration testing, should be the basis. Fourth, who designed it? CSIRO calls footing remediation the realm of a specialist consultant.

What no source we found establishes is how a screw pile is connected to an existing footing, how deep it goes under a house, whether it suits reactive clay, or what it costs or is warranted for. The NSW rules do apply: the Home Building Regulation's category is "underpinning or piering", defined for piering as putting in a column or post to support a superstructure such as beams or floor bearers, and a licence is needed above A$5,000.

Screw Piles in Sydney — common questions

Are screw piles better than other underpinning?

We found no independent source that says so, or the reverse. Published prices come from firms selling their own method, so the costs page shows none.

Is a torque reading enough to prove a pile?

A conference paper on screw pile capacity says no: measured torque relates to the soil the helix has already gone through, not to the soil beneath its base, so it should not be the only verification.

Do screw piles need a licensed contractor?

Underpinning or piering work valued above A$5,000 does. The Regulation does not mention screw piles, so ask for a licence number and the categories it covers.