Piling
Micro Piles / Grout Piles
Small-diameter drilled and grouted piles for tight sites, low headroom and work next to existing buildings.
Diameter: 150–600 mm
Overview
Micro piles, also called grout piles or mini piles, are small-diameter drilled piles. A compact rig drills a borehole to the design depth, a steel reinforcing bar or cage is placed in it, and the hole is filled with cement grout or concrete from the base upwards.
Because the rigs are small and drilling causes little vibration, micro piles suit places where a large piling rig cannot work: narrow urban plots, sites beside existing houses, basements with limited headroom and extensions to occupied buildings.
The piles carry load mainly through friction between the grouted shaft and the surrounding ground, so the number, length and diameter of piles are designed to suit the loads and the soil profile found in the site investigation.
Typical applications
- Houses and low-rise buildings on tight urban plots
- Extensions and additional floors on existing buildings
- Underpinning and strengthening existing foundations
- Sites with restricted access or low headroom
- Soft or filled ground over a firmer bearing layer
- Foundations for boundary walls, tanks and light structures
Our process
Review the site and design
We study the site investigation report and the structural drawings, and confirm pile positions, diameters and depths with the design engineer.
Set out and prepare
Pile positions are set out from the drawings and the working area is prepared so the rig can move safely between piles.
Drill to design depth
The compact rig drills each borehole to the design depth, using temporary casing where the ground needs support.
Place the reinforcement
The steel bar or cage is lowered into the borehole and held centrally.
Grout or concrete the pile
Grout or concrete is placed from the base of the hole upwards so the shaft is filled without voids.
Record and hand over
Each pile is recorded and the as-built information is handed over, ready for the pile caps.
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Frequently asked questions
What is a micro pile?
A micro pile is a small-diameter drilled pile, typically reinforced with a steel bar or cage and filled with cement grout or concrete. Our micro piles range from 150 to 600 mm in diameter.
When are micro piles used instead of larger bored piles?
Micro piles are chosen where access is restricted, headroom is low, vibration must be kept to a minimum or the loads are moderate — for example houses on narrow plots, extensions and underpinning work.
Can micro piles be installed right next to an existing building?
Yes. The rigs are compact and drilling causes little vibration, which is why micro piling is often used beside existing houses and for underpinning. The exact clearance depends on the rig and the site layout, so we confirm it during the site visit.
How deep do micro piles go?
The depth is set by the structural design and the ground conditions shown in the site investigation, so it varies from site to site. We drill each pile to the depth specified by the design engineer.