What Actually Makes a Good Screw Pile? The Science of Helix Design

Screw piles (also called helical piles) are a go-to foundation solution for residential, commercial and civil projects. Their performance depends not on steel quality alone, but on the helix design—the core factor that determines load-bearing capacity and stability.

Among all designs, the twin-helix (dual-helix) screw pile stands out for its superior stability, making it ideal for most projects in New South Wales (NSW) and beyond.

Why Twin-Helix Screw Piles? Key Advantages

Compared with single-helix piles, twin-helix screw piles offer two core benefits:

Better stability: The dual helix structure ensures uniform load distribution, avoiding tilting or shifting during use.

Higher load-bearing capacity: The increased contact area with soil enhances grip, making it suitable for various soil types (including clay, sand and loam).

4 Key Factors for a High-Quality Twin-Helix Screw Pile

Helix Size: Match the helix diameter to soil conditions—larger diameters (150-300mm) for soft/sandy soils, and appropriate thickness for dense/clay soils.

Helix Spacing: The distance between the two helices should be 2-3 times the helix diameter to avoid soil compaction and ensure load balance.

Material Quality: Use high-strength steel (Q355 or above) for both the shaft and helices; hot-dip galvanization is a must to resist corrosion.

Installation Precision: Install at the correct torque (based on soil density) and ensure vertical alignment to prevent tilting.

By focusing on these factors, you can ensure the twin-helix screw pile is reliable, durable and suitable for your specific project needs.