Contiguous piles have many advantages in the formation of a retaining wall. This method of construction involves the creation of a line of deep bores that are then back filled with concrete.

Of all the methods of piling Contiguous piling is typically the most cost effective and least time consuming. The wall consists of individual piles typically installed at centres 150mm greater than their diameter. This means that there are gaps between the piles and therefore contiguous piles are suitable only where the groundwater table is permanently below excavation level.

The waterproofing of contiguous piles can often be challenging. It is not possible to rely on a waterproof additive in the piles themselves. Likewise it is not possible to waterproof the pile externally.

Contiguous waterproofing piling cavity drainage membranes are the most reliable and effective method of waterproofing basement spaces however when used as the only waterproofing system with contiguous piled walls, special attention is require. It is important to minimise the workload of the groundwater drainage system and any pumps. Also it is crucial that earth from between the piles does not wash out into the drainage system and cause blockages.

It's vital therefore important to maximise the structural water tightness of the wall, this can be achieved using a poured or a spray concrete liner in front of the piles.