Introduction
Scaffolding, formwork, shoring, and underpinning are essential temporary or supporting systems used during building construction, repair, alteration, and structural strengthening. Although they may not remain visible in the finished building, they play a major role in ensuring safety, accuracy, stability, and construction efficiency.
Scaffolding provides temporary working platforms for workers and materials at height. Formwork gives shape and support to fresh concrete until it becomes sufficiently strong. Shoring temporarily supports unstable structures, excavations, walls, floors, or formwork during construction. Underpinning, on the other hand, strengthens or deepens an existing foundation when the original foundation is inadequate or when changes in loading or ground conditions affect structural stability.
These systems must be carefully designed and erected because their failure can cause serious accidents, structural damage, delays, and financial losses.
Scaffolding
Scaffolding is a temporary framework constructed around or inside a building to provide safe access and working platforms for construction workers.
It is commonly used for:
Brickwork
Plastering
Painting
Cladding installation
Repair and maintenance
Window installation
Structural work
Inspection of tall buildings
Scaffolding may be made from steel tubes, aluminium members, timber, bamboo, or prefabricated modular components.
Modern construction generally uses steel or aluminium systems because of their strength, durability, and reusability.
Main Components of Scaffolding
A typical scaffolding system contains several basic components.
Standards are the vertical members that transfer loads to the ground.
Ledgers are horizontal members running parallel to the building.
Transoms are horizontal members placed at right angles to the ledgers and support the working platform.
Braces provide diagonal stability and prevent sideways movement.
Base plates are placed below vertical standards to distribute loads.
Sole plates may be placed beneath base plates where the ground is soft.
Working platforms are constructed from boards, metal decks, or prefabricated units.
Guardrails and toe boards improve worker safety by preventing falls and materials from slipping off the platform.
Ties connect the scaffolding to the building and help prevent overturning.
Types of Scaffolding
Single Scaffolding
Single scaffolding is commonly used for brick masonry.
A single row of vertical standards is placed parallel to the wall. Putlogs or horizontal members extend from the standards into openings in the wall.
This system is relatively simple and economical for low- and medium-height brickwork.
Double Scaffolding
Double scaffolding is often used for stone masonry because creating putlog holes in stone walls may be difficult.
Two rows of standards are provided, making the system stronger and more independent of the wall.
Cantilever Scaffolding
Cantilever scaffolding is used where the ground directly below cannot support vertical standards.
The working platform is supported by needles or projecting structural members.
This type may be necessary near busy streets, weak ground, or locations where lower-level access must remain open.
Suspended Scaffolding
Suspended scaffolding consists of a platform suspended from the roof by ropes, chains, or cables.
The platform can often be raised or lowered mechanically.
It is commonly used for painting, façade maintenance, window cleaning, and repair of tall buildings.
Mobile Scaffolding
Mobile scaffolding is mounted on wheels and can be moved within a work area.
It is suitable for indoor finishing, services installation, and maintenance activities.
The wheels must be locked before workers use the platform.
Safety in Scaffolding
Scaffolding safety is extremely important.
A safe scaffold should have:
Stable foundations
Proper bracing
Secure connections
Adequate guardrails
Safe access ladders or stairs
Suitable platform width
Correct load capacity
Regular inspection
Protection against falling objects
Scaffolding should not be overloaded with excessive materials or equipment.
Workers should also use appropriate personal protective equipment and fall-protection systems where required.
Formwork
Formwork is a temporary or permanent mould into which fresh concrete is placed to obtain the desired shape and dimensions.
Concrete remains plastic immediately after mixing and therefore requires support until it gains sufficient strength.
Formwork is used for:
Columns
Beams
Slabs
Walls
Staircases
Foundations
Retaining walls
Shells and curved structures
Good formwork should produce accurate dimensions and a satisfactory concrete surface.
Requirements of Good Formwork
A good formwork system should have several characteristics.
It should be strong enough to resist:
Weight of fresh concrete
Reinforcement weight
Construction workers
Equipment
Vibration
Impact loads
It should also be rigid enough to prevent excessive deformation.
Formwork joints should be sufficiently tight to prevent leakage of cement slurry.
The system should be easy to assemble and dismantle without damaging the concrete.
Where reuse is expected, it should also be durable and economical.
Materials Used for Formwork
Timber Formwork
Timber is a traditional formwork material.
It is easy to cut and adapt to different shapes, making it useful for small and irregular projects.
However, timber may absorb moisture, warp, or deteriorate and generally has a limited number of reuses.
Plywood Formwork
Plywood is widely used as a sheathing material because it creates relatively smooth concrete surfaces.
Film-faced plywood is commonly used where multiple reuses are required.
Steel Formwork
Steel formwork is strong, durable, and suitable for repeated use.
It produces smooth surfaces and consistent dimensions.
However, it is relatively heavy and may require lifting equipment.
Aluminium Formwork
Aluminium formwork is lighter than steel and suitable for repetitive building layouts.
It is widely used in mass housing and high-rise construction where walls and slabs are cast in repeated cycles.
Plastic and Modular Formwork
Plastic systems are lightweight and corrosion-resistant.
They are especially useful for repetitive low-rise construction and modular applications.
Formwork for Different Structural Elements
Column formwork usually consists of vertical panels held together with clamps or ties.
Beam formwork includes side panels and bottom soffit support.
Slab formwork consists of panels supported by joists, props, or scaffolding systems.
Wall formwork uses large vertical panels tied together to resist lateral pressure from wet concrete.
The pressure exerted by fresh concrete can be significant, especially during rapid pouring. Therefore, formwork spacing, ties, and supports must be carefully designed.
Stripping of Formwork
Formwork should not be removed until the concrete has gained enough strength to support itself and any expected construction loads.
Removal time depends on:
Cement type
Concrete strength
Temperature
Span
Structural element
Curing conditions
Premature removal can lead to excessive deflection, cracking, or collapse.
The sequence of stripping should therefore follow structural and construction specifications.
Shoring
Shoring is the temporary support provided to a structure, excavation, wall, slab, or formwork when there is a risk of movement or collapse.
It is commonly required during:
Building alteration
Excavation
Demolition
Repair work
Formwork support
Foundation work
Wall replacement
Construction near existing buildings
Shoring systems may use timber, steel, hydraulic props, or engineered modular components.
Types of Shoring
Raking Shoring
Raking shoring uses inclined supports called rakers.
The rakers transfer lateral forces from an unstable wall to the ground.
It is commonly used when walls show signs of instability during repairs or alterations.
Flying Shoring
Flying shoring provides horizontal support between two parallel walls.
It may be used when an intermediate structure is removed or when adjacent walls require temporary stabilization.
Dead Shoring
Dead shoring consists of vertical supports used to carry loads temporarily.
It is often used when lower sections of walls are removed, openings are created, or foundations are repaired.
Shoring for Excavations
Deep excavations may require temporary earth-retaining systems to prevent soil collapse.
Common methods include:
Timber sheeting
Soldier piles and lagging
Sheet piles
Diaphragm walls
Secant pile walls
Struts and walers
Ground anchors
The choice depends on excavation depth, soil conditions, groundwater, nearby buildings, and site constraints.
Underpinning
Underpinning is the process of strengthening, stabilizing, or extending an existing foundation.
Unlike shoring, which is mainly temporary, underpinning generally becomes a permanent part of the structure.
It may be required when:
Existing foundations are inadequate
Additional floors are added
Structural loads increase
Nearby excavation affects the foundation
Soil settlement occurs
Foundation movement causes cracks
Basement depth is increased
Ground conditions change
The aim is to transfer the building load to stronger or deeper soil strata.
Mass Concrete Underpinning
Mass concrete underpinning is a traditional technique.
Small sections beneath the existing foundation are excavated sequentially and filled with concrete.
Work is carried out in controlled stages to avoid destabilizing the building.
This method is suitable for relatively shallow foundations and moderate strengthening requirements.
Beam and Base Underpinning
In the beam-and-base method, a reinforced concrete beam is constructed beneath or alongside the existing wall.
The beam transfers loads to new concrete bases or deeper supports.
This technique may be used where load distribution needs to be improved.
Mini-Pile Underpinning
Mini-pile underpinning uses small-diameter piles installed beneath or adjacent to existing foundations.
These piles transfer loads to deeper, stronger strata.
The method is especially useful where:
Access is restricted
Existing loads are high
Weak soil extends to significant depth
Vibration must be minimized
Mini-piles can be installed using relatively compact equipment and are widely used in urban refurbishment projects.
Needle Beam Underpinning
Needle beams may be inserted through or beneath walls to temporarily transfer structural loads to new supports while foundation work is carried out.
This method requires careful sequencing and monitoring.
Difference Between Shoring and Underpinning
Although the terms are sometimes confused, they have different purposes.
Shoring provides temporary support to prevent collapse or movement during construction or repair.
Underpinning permanently strengthens or deepens an existing foundation.
For example, if a cracked wall needs temporary support during repair, shoring may be used. If the cracking is caused by an inadequate foundation, underpinning may be required to correct the underlying problem.
Importance of Temporary Works Design
Scaffolding, formwork, and shoring are often classified as temporary works, but they must be designed with the same seriousness as permanent structures.
Failures can occur due to:
Weak connections
Inadequate bracing
Poor foundations
Overloading
Incorrect erection
Premature removal
Unplanned construction sequences
Poor-quality materials
Temporary works should therefore be designed, inspected, and supervised by competent personnel.
Inspection and Maintenance
Regular inspection is essential throughout construction.
Scaffolding should be checked after erection, alteration, severe weather, or accidental impact.
Formwork should be inspected before concrete placement to ensure correct line, level, support, and joint tightness.
Shoring systems should be monitored for settlement, deformation, or loosening.
Underpinning work may require crack monitoring, settlement measurements, and structural observation.
Good documentation improves safety and helps identify problems before they become critical.
Conclusion
Scaffolding, formwork, shoring, and underpinning are fundamental components of safe and efficient construction. Scaffolding provides secure access and working platforms, while formwork shapes and supports fresh concrete until sufficient strength develops. Shoring stabilizes structures and excavations temporarily, whereas underpinning permanently strengthens or deepens existing foundations.
Although many of these systems are temporary, their design and execution have a direct impact on construction safety and structural quality. Proper material selection, load assessment, bracing, sequencing, inspection, and skilled workmanship are therefore essential.
Modern construction increasingly uses modular scaffolding, engineered formwork, hydraulic shoring, and mini-pile underpinning to improve speed, accuracy, and safety. However, regardless of the technology used, the basic principle remains the same: temporary and supporting systems must safely control loads and maintain stability throughout every stage of construction.
