What micro piles are, and when engineers specify them.

What to know about micro piles and how the method works.

A micro pile earns its capacity from bond rather than bulk. A compact rig drills a small diameter hole through the problem soils, through obstructions if necessary, down into competent material. High strength steel, a threaded bar or casing, goes the full depth of the hole, and grout is pumped in around it. As the grout cures, it bonds the steel to the ground along the length of the pile, so load applied at the top sheds into deep, stable strata through that bonded interface. Engineers specify micro piles when a site rules out other systems, and the design comes from the structure's loads and a geotechnical reading of the ground. Our own deep foundation work uses helical piles screwed to depth and hydraulically driven push piers, both part of the wider family of foundation systems that reach deep soil. On any site, the specialist looks at access and at how weak the surface soil is, and the elevation survey at the evaluation shows how far the structure has moved before anyone recommends a system.

The symptoms that usually lead to micro piles are on the foundation repair problem signs page, alongside the other signs that point to the same underlying cause.