Piled Rafts require a slab to be supported on piles. In underpinning applications the slab is toothed into the wall of a building, divorcing it from its previous foundations. Loss adjusters frequently choose this option to overcome subsidence or settlement problems.
Combining piles and traditional underpinning makes it possible to provide deep foundations where none existed before. This technique is used when traditional underpinning becomes uneconomic or unsafe, i.e. where the suitable bearing strata is deeper than 2m.
This application is becoming increasingly popular where new construction work is being undertaken over existing drains or tree roots. The slab edge can be left square, have a ‘boot’ detail to hide the concrete edge, or be fitted with a steel angle to take the external course of brickwork. This method saves costs and time of installing ground beams and the added expense additional disposal of arisings.