The use of mini-piles as a method of underpinning is relatively new since there has been a reluctance to use small diameter piles in ground conditions which may vary appreciably. Nonetheless mini-piles have certain advantages when used to underpin existing structures. In particular, the relatively small diameter holes can be drilled through the existing foundations allowing individual mini-piles to be placed at points of maximum loading. The manoeuvrability of purpose-built plant and equipment allows work to be undertaken at low cost and without excessive disruption.