Welcome to building.co.uk. This site uses cookies. Read our policy.

Types of piling
Bored piling
TypeShaft Diameter (mm)Max depth (m)Remarks
Tripod400-60030Installed using simple, lightweight rigs. Ideal for confined spaces
Continuous flight auger (CFA)300-90027.5Quiet, quick and economical method of boring. Only suitable for soft ground conditions
Rotary/bored300-300065Hydraulic rigs for load-bearing and walling solutions. Ideal for tougher ground conditions and obstructions
Driven piling
TypeTypical shaft size (mm2)Max depth (m)Remarks
Precast concrete230 and 270UnlimitedInstalled by hydraulic hammers. Piles are cast in 5-15 m lengths. Greater depth achieved by joining piles
Driven steel section130-450Unlimited with splicing connectionsAvailable in high strength or corrosion-resistant steel. Advantage of being able to penetrate bedrock. Steel lugs can be welded to the pile to give it a higher friction load capacity
Sheet pilingN/A18 m in cohesive soil. 12 m in granular soilSheet piling can be used as a cost-effective method of soil retention in temporary and permanent applications.
Diaphragm walling
TypeTypical wall thicknessMax depth (m)Remarks
Diaphragm walling600-150050Ideal for constructing basement boxes, underpasses etc. Frequently used with bored piles and plunged columns in “top-down” construction.
Ground engineering
TypeTypical shaft diameter (mm)Max depth (m)Remarks
Mini100-30035Ideal in confined areas
Anchors100-30035Permanent and temporary applications
Soil nails100-30025Ideal for stabilising slopes
Bored-pile retaining walls
Used for the construction of temporary or permanent retaining walls and for the provision of deep basements, underground structures and motorway cuttings. Bored-pile retaining walls are either “contiguous” or “secant”, the choice determined by soil type, ground water profile, maximum retained heights, programme, propping requirements, cost and life span.
TypeShaft diameter (mm)CentresMax depth (m)
ContiguousUp to 1200 for CFA. Up to 2400 for rotaryGenerally 150 mm greater than diameter of the piles, thereby leaving gaps.20 (can be extended with larger pile spacing)
SecantCFA/ rotary - generally 500-900Less than the diameter, creating interlocking20 (30 can be achieved but difficulties may be encountered)
Case studies
LocationPile typeAverage length (m)Diameter (mm)No. of piles Approximate cost (£)
Per metreAverage per pileSetup per pile
LondonCast in-situ reinforced concrete, lined, auger bored28.57509950143775
Cast in-situ RC, CFA bored17.5350178173000
ClevelandCast in-situ RC, CFA bored134501533039025
LondonCast in-situ, temporary casing, rotary bored153201724668730
BristolMini piles1930015667126536
Driven RC square section13285 x 2853332127536
ManchesterRC secant pile wall, CFA/rotary bored18 hard 880 3481371717included
7 soft750     
LondonRC secant pile wall, CFA/rotary bored17 hard 600 5251071496included
11 soft600     
LondonCast in-situ RC, rotary bored35600-1050127198694455
Costs exclude general preliminaries. Costs current at fourth quarter 2004