What a screw pile is
A screw pile is a steel tube with one or more helix plates near its tip and a point to guide it in. A hydraulic drive head turns it into the ground, much like a screw going into timber. The helix pulls the pile down with very little disturbance to the soil around it.
When the pile reaches firm ground it gets harder to turn. That resistance is what tells us it's ready to carry load.
Two kinds
Screw piles come in two main types, and we use both:
- Ground screws have a thread running along a tapered shaft. They're quick to install and suit lighter structures: decks, sheds, fences, signs and solar mounts.
- Helical piles have a straight shaft with one or more large helix plates near the tip. The plates bear on firm soil further down, so they carry houses, extensions and heavier buildings.
- When the firm layer is deeper than expected, an extension bolts on and the pile keeps going down.
How it carries load
Most of the load goes through the helix plates into the soil beneath them, like a small footing buried deep in the ground. Some is carried by friction along the shaft.
Because the plates are locked into the soil, the pile resists being pulled up as well as pushed down. That matters for decks, carports, signs and anything else the wind tries to lift.
Why the torque matters
The firmer the ground, the more twisting force (torque) it takes to turn the pile. The link between installation torque and the load a pile can carry is well established, so the final torque is a direct check on every pile.
We record the depth and final torque of each one. For consented work the engineer sets a target torque, and we keep going, adding an extension if needed, until every pile reaches it.
How much can a screw pile carry?
What goes on top
Each pile is cut to level, then fitted with whatever the structure needs: an adjustable saddle for timber bearers, a cap plate for steel posts and portal frames, or a bracket kit for decks and sheds. There's nothing to cure, so the builder can start straight away.
When they're not the answer
Solid rock close to the surface, large boulders and some buried services can stop a pile going where it's needed, and very heavy loads may need a different foundation. We check every site first, and we'll tell you if concrete suits it better.