A micropile is a small-diameter, drilled and grouted deep foundation element, typically reinforced with steel, used to transfer structural loads to deeper, more competent soil or rock. Its compact size allows installation with smaller equipment than conventional piles require, making it useful in restricted-access sites.
Despite their small diameter, micropiles can achieve surprisingly high load capacities relative to their size, thanks to the high-strength steel reinforcement and cement grout bond along their length.
What Does a Micropile Involve?
- A small-diameter drilled hole
- A steel reinforcing bar or casing inside
- Cement grout filling the drilled shaft
- Compact drilling equipment suited to tight spaces
Why Are Micropiles Important?
Micropiles can be installed in locations where larger pile-driving equipment simply can’t fit, such as inside an existing basement, beneath a low-clearance structure, or in a densely built urban lot. This makes them a common solution for underpinning an existing foundation that’s settling, since the small equipment footprint allows work to happen without demolishing surrounding structures or requiring wide equipment access.
Because the drilling and grouting process is also relatively quiet and low-vibration, micropiles are frequently chosen for historic building preservation, where minimizing disturbance to fragile original structures matters as much as the structural outcome itself. Because they can be installed at almost any angle, including battered or inclined orientations, micropiles are also useful for resisting lateral or uplift forces in ways that a purely vertical foundation element sometimes can’t. Testing a sample of installed micropiles under load is common practice on larger projects, confirming the design capacity before the remaining piles are relied upon structurally.
Micropile vs. Helical Pile
A helical pile is mechanically screwed into the ground, while a micropile is drilled and then filled with grout around a steel reinforcing element. Both suit tight-access sites, but micropiles can typically achieve higher load capacities in harder or rockier ground conditions.