Difference between Scaffolding and Formwork
Scaffolding and formwork are both temporary structure made during the time of construction of the different structure like building, bridge, culvert etc. Let us see both of them one by one.
|Materials used||They can be made from timber, steel, and aluminum.||They can be made from wood, plywood, steel, combined wood-steel, reinforced concrete, and plain concrete.|
|Usage||Around the building or structure to perform various works like painting, whitewashing, plastering, and so on.||Used as a mould to construct concrete columns, beams, slabs, and so on.|
|Removal||They can be removed as soon as the work is completed.||They should be removed after 36 hours or 6 days or 28 days depending upon the type of formwork.|
Details of Scaffolding and Formwork
What is Scaffolding?
Scaffolding is a type of temporary construction that is used for access around the building when the height of the building exceeds about 1.5 m.
These temporary structures are very close to the walls of the building. They should be strong enough to hold workmen and other materials placed on it.
Functions of scaffolding
- These are needed to support the platform over which the workmen can sit and carry the construction.
- These are also needed when a building needs repairing or a building should be demolished.
Components of Scaffolding
- Standards: They are the vertical members resting on the ground.
- Ledgers: They are horizontal members running parallel to the walls.
- Braces: They are diagonal members fixed on the standards to make scaffolding stable.
- Putlogs: These are transverse member perpendicular to the wall surface with one end on the ledger and other on the wall.
- Transoms: These are transverse member perpendicular to the wall whose both end is on the ledger.
- Bridle: A member used to bridge a wall opening that supports one end of the putlog at the opening.
- Boarding: This is a horizontal member that rests on putlogs to support the workers and materials.
- Guard rail: This is a rail parallel to the ledgers at the working level.
- Toeboard: This is a board parallel to the ledgers which are supported on putlogs for protection.
- Rope-lashings, nails, bolts, and so on are used to secure the various components.
- Operational work should follow safety regulations.
- Materials used for scaffolding should be inspected before use.
- Materials such as timber, steel and aluminium can be used to construct a scaffolding.
- Guard Rail should be of more than 2 metres height.
Types of Scaffolding
Scaffolding is of following types:
- Single scaffolding or brick-layers scaffolding
It consists of a single framework of different scaffolding components. It is built parallel to the wall at a distance of 1.2 meters. This type of scaffolding is also used for bricklaying and called putlog scaffolding.
- Double scaffolding or masons scaffolding
This type of scaffolding consists of two rows of scaffolding. It is used in places where cheap single scaffolding cannot be used. It is also called an independent scaffolding.
- Cantilever or needle scaffolding
When the ground is weak to support standards and construction is to be carried out in the upper part of the building near the wall, cantilever scaffolding comes to use.
- Suspended scaffolding
This type of scaffolding is very light and used for light works such as painting, pointing, whitewashing, distempering and many others.
- Trestle scaffolding
Trestle scaffolding is used for painting and repair works. They are normally used up to a height of 5 metres.
- Steel scaffolding
This type of scaffolding is similar to timber scaffolding. Steel and rope-lashings are used in place of timber this type of scaffolding can be used to any height.
Among scaffolding and formwork, we have completed Scaffolding. Now, let us discuss formwork.
Formwork, also known as shuttering is a temporary construction which is used as a mould for different structures like column, beam, slab, stairs and so on, in which concrete is placed and hardened and matured.
Formwork is too much money expending and time-consuming phase in construction. It’s expenses increase more in a huge structure like a dam, reservoir, and bridge.
Function of formwork
There is a huge difference between the function of scaffolding and formwork. The formwork work as a mould to concrete and helps to provide shape size and strength to the freshly made viscous concrete.
Characteristics of a good formwork
- It should be strong enough to withstand different forms of loads such as a dead load of concrete and live load during and after casting concrete.
- It should be leakage proof.
- It should be waterproof.
- It should be rigid enough to avoid deflection.
- It should be as light as possible.
- The materials used for making formwork should resist warping, bulking, and weather.
- The materials used for the construction of formwork should be easily available, cheap, and reusable.
Loads on formwork
- The deadweight of green concrete (2300-2400 kg/m³).
- The hydrostatic pressure of the green concrete.
- Live load due to working labour (400 kg/m²).
- Impact effect at the time of pouring concrete, compacting concrete by mechanical equipment (vibrator, needle vibrator, plate vibrator and so on.)
The material used for Formwork
They can be made of wood, plywood, steel, combined wood-steel, reinforced concrete and plain concrete.
Types of formwork
Formwork is classified based on where they are used. Some of them are briefly described below:
- Formworks for excavation and trenches
This type of formwork is used when the depth of trench is large or when the sub-soil is loose by a method called timbering of trenches. It helps to prevent the trench to cave in.
Methods of timbering
- Stay Bracing
This method is used when excavation does not exceed 2 meters for supporting the sides or bench excavated in firmly firm soil. It consists of vertical sheets placed at the interval of 2 to 4 meters which extends to the full height of trench.
- Box sheeting
This method is used when excavation does not exceed 4 meters in loose soil. It consists of vertical sheets placed very near to each other.
- Vertical Sheeting
This method is used for deep trenches of around 10 meters in depth. It is similar to box sheeting. In this type, the excavation is carried out in stages and an offset is provided after the stages.
This method is used in emergency condition if the soil where excavation is going on has extremely loose and soft ground.
- Sheet piling
This method is used when soil to be excavated is soft or loose where the depth and width of excavation is large and has sub-soil water.
- Formworks for column footing
Formwork to be used for column footing depends upon the shape of footing. Usually, square and rectangular formwork is used accompanied by vertical sides or steps of sloping sides.
- Formwork for columns
Formwork for columns includes four boxes prepared for four sides which are assembled and concrete is poured and cured and removed after maturing.
- Formwork for floors
Formwork for floors consists of a skeleton to receive concrete usually made of small wooden beams at top and rows of vertical posts.
- Formwork for beams
Formwork for the beam is a type of formwork similar as formwork for floors.
- Formwork for stairs
Formwork for stairs consists of stringers, sheets, joists, bearers and vertical post.
Time for Removal of formwork
|Vertical formwork (side of beam)||36 hours|
|Slab soffit||6 days|
|Removal of the prop of beam||15 days|
|Total removal||28 days|
Stripping: operation of removing formwork.
Panel forms: formwork whose can be used several times.
Stationary forms: formwork that is made for individual non-standard members and structures which have no repeatable elements and cannot be stripped.
Green concrete: concrete with water whose initial setting has not done.
Why we prefer steel formwork over timber formwork?
It is because there is less possibility of warping, swelling, and shrinkage of steel. Steel has a smooth surface and has greater rigidity than timber. Though steel formwork is costlier, it possesses greater advantages over timber formwork.
I hope this article on scaffolding and formwork remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Sushmita Niraula