Piling: A Complete Guide

Piling is a deep foundation technique used in construction to transfer loads from a structure into deeper, more stable soil or rock layers beneath the surface. Rather than relying on the bearing capacity of the ground immediately underfoot, piling reaches down to firmer strata that can reliably support whatever is being built above.

More broadly, the term covers any driven or installed structural element used to stabilise, support, or retain ground, from the deep concrete columns that underpin bridges and high-rise buildings, to the steel sheet walls that protect open excavations and hold back groundwater during underground construction work.

Sheet piling specifically involves driving interlocking steel sheets into the ground to form a continuous retaining wall. It is one of the most widely used methods in UK groundworks and civil engineering, deployed across utility trenches, highway crossings, cofferdams, waterway works, and marine structures.

Ground conditions on UK construction sites are rarely straightforward. Made ground, soft clays, waterlogged soils, and variable fill can all threaten the stability of an excavation and the safety of the people working in and around it.

Sheet piling addresses these risks directly by creating a structural barrier that:

• Prevents excavation faces from collapsing inward

• Controls groundwater ingress during below-ground works

• Limits ground movement and protects adjacent structures and buried services

• Creates a compliant, safe working environment for operatives in trenches and deep excavations

Without adequate earthwork support, ground can shift without warning. The consequences range from project delays and material loss to structural damage to nearby buildings, or serious injury to site workers. Piling is how site teams manage that risk systematically and to standard.

Piling covers several distinct methods, each suited to different site conditions, structural requirements, and constraints.

Driven Piling

Preformed steel, concrete, or timber piles are hammered or pressed into the ground by machine. Fast to install and suitable for a wide range of ground conditions, driven piling is well-suited to sites with high production requirements and enough space for plant access.

Bored (Rotary) Piling

A hole is drilled into the ground and filled with reinforced concrete. Unlike driven methods, bored piling generates minimal vibration, making it appropriate for sensitive urban environments or sites close to existing structures. Primarily used for load-bearing foundations.

Continuous Flight Auger (CFA) Piling

One of the most widely used foundation methods in the UK, CFA piling drills and concretes in a single continuous operation. Low-vibration, relatively quiet, and suitable for most soil types, and commonly specified for residential, commercial, and infrastructure foundations.

Sheet Piling

Steel sheets with interlocking or overlapping profiles are driven into the ground side by side to form a continuous wall. Sheet piling is used for both temporary and permanent applications, including:

• Temporary excavation support: trenches, basements, cofferdams, attenuation tanks

• Permanent retaining walls and embankment support

• Waterway bank reinforcement and canal lining

• Marine structures including harbour walls, jetties, and waterfront reinforcement

• Cut-off barriers to control the migration of groundwater

Temporary sheet piles can be extracted and reused once works are complete, making them a sustainable and cost-effective solution for short-duration operations. Sheet piling is the primary form of piling relevant to the hire and supply of groundworks equipment.

Contiguous and Secant Pile Walls

Bored piles installed side by side to form a retaining wall. Contiguous walls leave a small gap between piles; secant walls overlap. Used for deep urban excavations and basement construction where a robust permanent wall is required.

Choosing the right sheet pile specification and the right installation method depends on several site-specific factors. Involve a structural engineer for permanent works or complex temporary works designs.

Soil Conditions

Soft clays, silts, and waterlogged soils are generally well-suited to driven sheet piling. Sandy and granular ground also presents few problems. Dense, rocky, or highly cohesive ground may require specialist equipment or a higher-yield pile profile. A ground investigation report should inform all piling decisions.

Load Requirements

A light utility trench in shallow ground calls for a very different specification to a deep cofferdam or marine retaining wall. The pile's section modulus (its resistance to bending under lateral soil and water pressure) must be matched to the loads in play. Higher section modulus means greater bending resistance and suitability for deeper or more demanding applications.

Site Access

Tight sites, restricted working widths, or overhead obstructions limit the size of plant that can operate. Where access is confined, lighter sheet profiles that can be handled and pitched without heavy plant may be preferable. Plan for the clearance requirements of piling hammers and vibratory drivers from the outset.

Environmental Factors

Proximity to existing buildings, sensitive buried services, or environmentally protected areas affects method and equipment choice. Vibratory driving produces less ground vibration than impact methods and is widely preferred on urban sites. Where noise is a concern, hydraulic press-in systems reduce disturbance further. The reusability of steel sheet piles also means significantly less material waste compared to cast-in-situ alternatives.

Project Timeline and Budget

Sheet piling is generally faster to install than bored or cast-in-situ alternatives for linear applications such as road crossings and utility trenches. Hire options allow contractors to take exactly what they need without the capital outlay of purchase. For longer programmes, or contractors who regularly work in similar conditions, sale or sale-and-buyback arrangements offer better value over time.

Altrad Generation supplies a range of sheet piles and piling ancillaries for hire and sale, covering temporary and permanent works in groundworks, civil engineering, and utilities.

Sheet Piles

L8 Interlocking Trench Sheets

Lightweight mild steel interlocking sheets with an effective width of 432mm per sheet and a bending moment of 8.22 kNm/m. The interlocking clutch profile locks adjacent sheets mechanically, reducing water inflow across the retained face. Well-suited to standard-width utility trenches, temporary earth retention, and permanent waterway bank reinforcement where a lighter, easier-to-handle section is appropriate. Galvanised versions available on request. Available in five lengths from 2,000mm to 6,000mm.

Larssen Range Interlocking Trench Sheets

Heavy-duty interlocking steel sheet piles for temporary and permanent civil works. Seven profiles cover section moduli from 742 cm³/m (L601) to 3,200 cm³/m (L607), making this range suitable for medium retaining walls through to major cofferdam designs, canal lining, and marine structures. Interlocking joints form a continuous, watertight wall capable of restricting groundwater inflow under significant hydrostatic pressure. Proper specification requires evaluation of pile length, penetration depth, and ground loading.

BVI500 Interlocking Trench Sheets

High yield steel interlocking sheets with integrated clutch profiles that lock adjacent sheets together mechanically. With a bending moment of 50.3 kNm/m, the BVI500 offers significantly higher lateral resistance than the L8 and is suited to deeper excavations, waterlogged ground, and projects where ground movement must be kept to a minimum. Appropriate for permanent and temporary applications including earth bank support, deep utility installations, and works adjacent to existing structures. Available in eight lengths from 2,500mm to 6,000mm.

Ancillaries

Driving Caps

Steel caps that fit over the head of a trench sheet to protect it from deformation and damage during driven installation. Absorb impact from hydraulic, vibratory, and manual hammering equipment, extending sheet service life across repeated installation and extraction cycles. Available in three variants (Universal, BD, and HD) to suit the full Altrad Generation trench sheet range.

Quick Release Pitching Shackle

Enables safe, ground-level installation of trench sheets. A spring-loaded pin mechanism grips the sheet through its lifting hole, allowing it to be positioned and driven into place before the operative releases it remotely from ground level, eliminating the need for anyone to approach a suspended load during installation. Safe Working Load is stamped on each unit for on-site identification. Available in 2-tonne and 3-tonne SWL variants, compatible with the BVI500, Larssen Range, KKD600, and BD500 trench sheets.

Extraction Clamps

Attach to trench sheets and transfer lifting force from excavators or cranes for controlled, damage-free sheet removal at the end of the works. Heavy-duty steel construction rated for repeated demanding use. Available in a standard 5-tonne version and an HD 7.5-tonne version for heavier or more deeply embedded sections. Compatible with the full Altrad Generation trench sheet range. **Note: for extraction only. Must not be used to pitch sheets.**

Q. What is the difference between sheet piling and foundation piling?
A. Foundation piling (such as CFA, driven concrete, or rotary bored piling) transfers the load from a structure down into deeper, stronger ground and is used to support buildings and infrastructure from below. Sheet piling forms a continuous vertical wall by interlocking individual steel sheets, and is primarily used to retain soil and groundwater around excavations. Both techniques are often used on the same project. For example, a sheet piled cofferdam may protect a bored pile installation from groundwater inflow while it is being formed.

Q. Can sheet piles be reused?
A. Yes. Temporary sheet piles are extracted once the works are complete and can be reused across multiple subsequent projects. This makes steel sheet piling one of the more sustainable options in temporary works: it leaves no permanent material in the ground, generates no concrete waste, and the steel can be recycled at end of life. Sheets should be inspected and any deformation assessed before each reinstallation.

Q. How deep can sheet piles be driven?
A. It depends on the pile profile, ground conditions, and equipment available. Standard trench sheet installations for utility works typically achieve 3–6 metres of penetration depth. Marine and civil infrastructure projects can require pile sections driven well beyond this. Larssen-type profiles are used in applications exceeding 20 metres in specialist settings. A structural engineer should calculate the required embedment depth based on retained height, soil properties, and the loading conditions specific to the site.

Q. What is the difference between overlapping and interlocking trench sheets?
A. Overlapping sheets are installed with their edges overlapping adjacent sheets. They are quick to install and suited to straightforward, drier excavations in relatively stable ground, but they do not form a watertight joint. Interlocking sheets, such as the BVI500 and L8, use a mechanical clutch profile that locks adjacent sheets together, creating a continuous wall that significantly reduces water inflow and limits ground movement between the piles. Interlocking profiles are the preferred choice wherever groundwater control or minimal lateral deflection is a priority.

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For more information on Altrad Generation's groundworks range, or to enquire about hire and sale options, contact [email protected].