Following our previous article on jumpform systems and their role in efficient and safe vertical construction, we turn our focus to precast, another key method for building structures.
While jumpforms are a key method in the construction of lift shafts and stair cores, precast elements offer an alternative approach that utilises off-site fabrication, rapid on-site installation, a high-quality finish and structural efficiency. These systems are increasingly being selected for modern projects, either in combination with jumpforms or as standalone solutions for vertical construction.
This article explores the benefits, installation process and practical applications of precast when compared to conventional methods.
Columns and walls which are vertical structural elements typically constructed of reinforced concrete and designed to support floor slabs. Similarly, walls are often designed to resist lateral forces such as wind and seismic loads.
Cores which are also typically constructed of reinforced concrete and form the structural backbone of a building, often home to lift shafts and stairwells.
Examples of precast applications are shown below:
Precast is initially adopted in the design development stages of a project. A specialist contractor is appointed to evolve the design. This will include the method of fixing the precast. An example is a “coupler” connection allowing the precast to be installed ahead of slab pours - as shown in figure 1 and 2 above.
Once the design is concluded, precast elements are then produced offsite using reusable formwork, reinforcement cages and controlled curing processes. Once cured, they are transported to the site and lifted into position using cranes.
Key installation steps include:
The off-site fabrication and modular approach reduce on-site work, minimising formwork and reinforcement labour demand which offers assurances around construction programmes.
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Rapid Installation: Precast elements can be installed quickly once foundations are ready, shortening programme durations.
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Lead Time: Requires early procurement where elements are required from the starting levels of a construction project, for example from the foundations.
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High Quality: Factory-controlled conditions ensure dimensional accuracy, smooth finishes and consistent quality.
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Transport and Lifting Constraints: Size and weight require careful logistics and appropriate crane capacity and access.
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Safety: Reduced on-site casting lowers exposure to formwork hazards, loose reinforcement loads and wet concrete.
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Planning Sensitivity: Requires detailed coordination of delivery schedules and installation sequence.
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Reduced Waste: Standardised production minimises material wastage and environmental impact.
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Initial Investment: Mold fabrication, precast yard and crane equipment require upfront costs.
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Versatility: Columns, core and walls can be designed for both structural and architectural purposes.
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Design Flexibility: Changes after fabrication can be costly or impractical.
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Traditional in-situ columns, cores and walls require on-site formwork, reinforcement placement, concrete pouring and curing. Moreover the double handling of formwork can add additional demand to crane utilisation. This method is labour intensive and can slow construction progress.
Precast elements allow parallel off-site fabrication and on-site installation, dramatically reducing construction time. Once foundations or formwork decks are ready, precast sections can be lifted into place, enabling subsequent floor slabs and beams to follow without waiting for stripping and curing times of vertical elements. Whilst this is not a limiting factor in all cases, for example in states where vertical elements are poured down with slabs, the double handling and on-site resource requirements are reduced.
A typical construction sequence for precast vs conventional:
From a construction planning perspective, precast offer strategic advantages, such as:
Versatile uses: It is not limited to use in high rise construction and can be used for various construction applications.
Efficiency: Off-site fabrication and rapid on-site installation provide programme assurance.
Safety: Reduced on-site casting and formwork hazards improve workforce safety.
Quality Control: Factory conditions ensure precise dimensions and also provide a high-quality finish.
Programme Predictability: Standardised elements simplify scheduling and resource allocation.
Structural Performance: Precast cores and walls provide excellent lateral stability for high-rise buildings.
From the graph above, precast construction allows faster vertical construction compared with conventional in-situ methods, similar to how jumpforms improve vertical core efficiency once operational.
The Zancon team has extensive experience across a variety of construction methods, allowing us to offer our Clients strategic solutions that combine the outcomes of efficiency, safety and quality when contemplating the approach to planning their projects.
Reach out to see how we can complement your team with our expertise and service offerings.