Geotechnical · 7 min read
Helical piles, screw piles and bored piers: choosing a footing system
When a slab or strip footing cannot get to good ground, you pile. Brisbane sites hit that point often: deep fill, soft alluvium over rock, steep slopes and reactive clays that move well below normal footing depth.
Helical and screw piles
A steel shaft with one or more helical plates, screwed into the ground with a hydraulic drive head. Capacity is verified from installation torque, so you get immediate proof of performance and can build the same day.
They suit deck and extension footings, underpinning, restricted access sites and work next to existing buildings where vibration is a problem. Corrosion allowance and torque-to-capacity correlation are the two things a design has to get right.
Bored piers and micropiles
Bored piers give high vertical and lateral capacity and are the default for retaining wall posts, house stumps into rock and larger loads. Micropiles suit low headroom and high capacity in tight spaces.
What the design has to demonstrate
Geotechnical capacity in end bearing and shaft friction, structural capacity of the shaft and connection, group effects and spacing, lateral and uplift demand from wind, settlement under service load, and durability for the design life.
That work relies on ground information. A soil test or borehole log makes the design cheaper and the pile lengths realistic; without it we design conservatively.
Fees
Footing and pile design starts at $800, including calculations, drawings and RPEQ certification. Send the soil report, structural loads or plans and site access details for a fixed fee.
Frequently asked questions
- Are screw piles cheaper than bored piers?
- Often on residential work, because installation is fast, spoil-free and needs smaller plant. For very high loads or where rock socketing is required, bored piers usually win.
- Do I need a soil test before pile design?
- Strongly recommended. Without ground data pile lengths are assumed conservatively, which costs more to install than the test would have cost.
Send your soil report for pile design from $800.
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