In the world of construction, many technical terms are often used interchangeably, which can lead to confusion. Three such terms are formwork, centering, and shuttering. While they all relate to temporary structures used during construction, they each have specific meanings and uses.
In this blog, we explain what each term means, how they differ, and why understanding them is important. We’ll also discuss their materials, types, and purpose in simple, easy-to-understand language.
What is Formwork?
Formwork is the general term for a temporary mould or structure into which fresh concrete is poured to shape it until it becomes strong enough to support itself.
It is like a cast for concrete. Formwork holds the concrete in place, gives it the desired shape, and maintains its position and alignment during curing. Once the concrete sets, the formwork is removed.
The word formwork is widely used as the overall name for all such temporary supporting structures in construction.
Types of Formwork
Formwork is the overall mould for concrete, and it can be classified based on material and construction:
a) Based on Material:
Timber Formwork – Made of wood or planks; easy to shape but less durable.
Plywood Formwork – Made of waterproof plywood sheets fixed on timber frames; gives smooth finish.
Steel Formwork – Made of steel plates; highly durable and reusable.
Aluminium Formwork – Lightweight, strong, and long-lasting; often used for repetitive work.
Plastic Formwork – Lightweight and easy to handle; suitable for simple, repetitive jobs.
Fabric Formwork – Special fabric sheets used in architectural or experimental construction.
b) Based on Structure:
Traditional formwork – Built on site, piece by piece.
Engineered formwork systems – Pre-fabricated panels and frames assembled on site; faster and more efficient.
What is Shuttering?
Shuttering is a specific part of formwork. It refers to the vertical or upright temporary structures that hold concrete in place on the sides.
For example:
- When building a column, the boards placed around its sides to hold the concrete are called shuttering.
- Similarly, in walls, the side panels are called shuttering.
In short, shuttering is the vertical or side portion of formwork, usually made of wood, plywood, steel, or plastic sheets. It stops the concrete from spilling out and keeps it in shape until it hardens.
Types of Shuttering
Shuttering refers specifically to the vertical formwork for walls, columns, and sides. Common types include:
Wall Shuttering – Vertical panels arranged to shape walls.
Column Shuttering – Usually made of four panels fixed around a column shape, square, rectangular, or circular.
Shear Wall Shuttering – Large vertical panels for high-rise shear walls.
Lift Shaft Shuttering – Vertical formwork designed for lift (elevator) shafts.
Shuttering can also vary by material: wooden, plywood, steel, aluminium, or plastic.
What is Centering?
Centering refers to the temporary horizontal supports used to hold concrete slabs, beams, or floors while the concrete is setting.
For example:
- When casting a floor slab, the boards and props arranged underneath to support the slab formwork are called centering.
- Similarly, in beams, the bottom horizontal boards and supports are centering.
In simple terms, centering is the horizontal or bottom portion of formwork, used for slabs, beams, and other horizontal structures.
Types of Centering
Centering is the horizontal formwork, mainly used to support concrete slabs, beams, and arches until they harden. The types of centering depend on the structure being supported:
Slab Centering – Horizontal panels supported on adjustable props, H-frames, or scaffolding to hold concrete slabs.
Beam Centering – Bottom and side supports for beams.
Arch Centering – Special curved formwork to support arch construction.
Circular Slab Centering – Used in domes or circular slabs, where curved formwork is needed.
Centering is usually made of timber planks, steel sheets on a frame, or even pre-engineered modular systems for speed and uniformity.
Difference Between Formwork, Shuttering, and Centering
| Feature | Formwork | Shuttering | Centering |
|---|---|---|---|
| Meaning | General term for moulds used to hold concrete | Vertical formwork for sides of structures | Horizontal formwork for slabs and beams |
| Direction | Both vertical and horizontal | Vertical only | Horizontal only |
| Example Use | Any mould in construction | Column sides, wall sides | Floor slabs, beam bottoms |
So, formwork is the overall name, while shuttering and centering are specific parts of formwork.
Materials Used in Formwork
Formwork, shuttering, and centering can all be made of the same materials. The most common ones include:
- Timber/wood: Easy to cut and assemble, but not durable for repeated use.
- Plywood: Smooth finish, lighter than wood, and reusable.
- Steel: Strong, durable, and reusable for many cycles. Gives a smooth surface finish.
- Aluminium: Lightweight and long-lasting.
- Plastic or fibreglass: Used in special shapes and light construction.
The choice of material depends on the budget, shape of the structure, and how many times the formwork will be reused.
Importance of Good Formwork
Good formwork is crucial because:
- It ensures the concrete retains its designed shape.
- It resists the pressure and weight of fresh concrete.
- It gives a smooth surface finish to the concrete.
- It saves time and reduces wastage.
Improper formwork can lead to honeycombing, leakage, cracks, and even structural failure.
Best Practices for Formwork, Shuttering, and Centering
✔ Make sure the formwork is strong, rigid, and properly supported.
✔ Apply oil or release agent to prevent sticking.
✔ Ensure the formwork is properly aligned and level.
✔ Remove the formwork only after the concrete has gained enough strength.
Relevant IS Codes for Formwork, Shuttering, and Centering
In India, the Bureau of Indian Standards (BIS) has published several codes that specify the recommended practices and guidelines for formwork, shuttering, and centering. Below are some important IS codes:
1. IS 14687:1999
Falsework for Concrete Structures — Guidelines
This standard gives guidelines for the design, erection, and removal of falsework (which includes centering and shuttering) used in concrete construction.
2. IS 4990:2011
Plywood for Concrete Shuttering Work — Specification
This code specifies the quality and requirements of plywood sheets used in shuttering and formwork.
3. IS 5525:1969
Recommendations for Detailing of Reinforcement in Reinforced Concrete Works
Though not directly about formwork, it provides details that influence the design of shuttering and centering.
4. IS 2750:1964
Specification for Steel Scaffolding
Steel scaffolding and props are often used to support centering and formwork.
5. IS 3696 (Part 1):1987
Safety Code for Scaffolds and Ladders — Part 1: Scaffolds
Safety while erecting and dismantling formwork, shuttering, and centering is essential. This code covers such safety measures.
6. IS 4014 (Part 2):1967
Code of Practice for Steel Tubular Scaffolding — Part 2: Safety Requirements
Guidelines for safe use of scaffolding that supports formwork and centering.
Conclusion🎯
To sum up, formwork is an essential part of any concrete construction. It is the general term for all temporary moulds, while shuttering refers to the vertical sides, and centering refers to the horizontal support. Choosing the right type of formwork, maintaining it properly, and using it correctly can ensure strong, smooth, and safe concrete structures.
FAQs on Formwork, Shuttering, and Centering
1. Are formwork, shuttering, and centering the same?
No. Formwork is the overall term for temporary moulds for concrete. Shuttering is the vertical part, and centering is the horizontal part of formwork.
2. Which is better — wooden or steel formwork?
Steel formwork is better if you want a smooth finish and plan to reuse it many times. Wooden formwork is cheaper but less durable.
3. When can formwork be removed?
Formwork should only be removed after the concrete gains sufficient strength. For slabs, it may take 7–14 days, and for vertical structures like columns, it may take 1–3 days.
4. Why is oil applied to formwork?
Oil or release agent is applied to prevent concrete from sticking to the formwork, making it easier to remove.
5. Can formwork be reused?
Yes, depending on the material and condition, formwork can be reused multiple times, especially steel and aluminium.