Precast Foundations (Piling) - Piling & Mini Piling Specialists

DWELLING HOUSES

This sheet is an outline of information for those considering piled foundations for dwelling houses and is prepared in good faith

As the availability of sites has become more limited and the cost of piled foundations has decreased, it is now commonplace to provide piled foundations for dwellings in ground unsuitable for traditional foundations.

In making the decision whether to pile or trench fill it is good practice to investigate the ground conditions by excavations using an excavator on rubber tyres or tracks. Rubber tyre excavators can usually dig to 13 ft and tracked machines to 20 ft. If either of these machines is at full depth then piling is almost certainly necessary. Early consultation with a civil or structural engineer experienced in soil mechanics is recommended.

Apart from the danger of deep dig, (health and safety regulations require excavations deeper than 1.2 metres to be propped), the breakeven point between piles and trench fill will depend on many other factors.

> Over-dig due to collapsing sides can result in a trench 3 to 4 times as wide as the bucket and a concrete cost to match

> The cost of spoil disposal and landfill tax

> The cost of shoring or risk of trench collapse, (particularly near other properties where piling is much safer than excavation below adjacent foundations)

> Ground water levels may make excavation at shallow depths impossible. (Lowering the water table by pumping groundwater can cause serious damage to adjacent buildings. It is not uncommon to drive piles as short as 2 metres rather than dewater and risk damage to adjacent property.)

Typically, we have found that clients find piles to be more economical than 2 to 3 metres of under-building.

If you have any questions regarding the information found on the website, please feel free to get in touch via one of the methods shown on the left.