Screw Piers on the Sunshine Coast

What screw piers on the Sunshine Coast actually involves

A screw pier is driven by machine rather than dug, and the installation torque gives a direct read on the capacity reached, which is the practical advantage over a poured footing because you find out what you have as you install it. QBCC's Foundation work (piling and anchors) licence class lists installing piling, including driven piles, cast-in piles, groutcrete piles, compressed piles and bored cast-in-place piles, and constructing underpinning. Screw piers are not named in that list, so ask the contractor which QBCC class they work under for the job.

How screw piers work

For a house, piers appear in one of two situations: a raise where new loads justify a properly engineered footing, or a repair where existing footings have failed and the ground near the surface has proved it cannot be trusted. In both, the pier schedule comes from an engineer, who sets the number of piers and the depth each must reach.

On the coastal plain a steel pier stays in ground close to the surf. In a CSIRO-authored national chloride dataset the only strong correlation with observed deposition was distance to the coast, so the coating specification is a question for the engineer against AS 4312, and this site assigns no corrosivity zone to any suburb. On a hinterland lot mapped as steep land (slopes of 15% or greater), the planning scheme's landslide code, where it applies, names a competent person's slope analysis or geotechnical investigation among its acceptable outcomes, which is where an engineer's pier schedule and a geotechnical assessment meet.

Screw Piers on the Sunshine Coast — common questions

Are screw piers better than concrete stumps?

They solve a different problem. Stumps carry the house above the footing; piers are the footing, used where shallow ground will not bear. On a block with competent ground near the surface they are unnecessary expense.

How deep do they go?

As deep as it takes to reach ground that will carry the load, which is why depth is not knowable before installation begins. Torque confirms capacity as the pier goes in.

Who decides how many piers are needed?

The engineer. Pier count and depth come from the ground and the loads, and installation torque confirms capacity as each pier goes in. QBCC's advice on quotes is to ask each contractor to price the same scope, so ask each to state the pier count they have priced.