Design: What is the basic difference between precast and prefabricated structures?
https://www.quora.com/Design/What-is-the-basic-difference-between-precast-and-prefabricated-structures
Let me start your answer by giving you the basic definitions of the two terms.
Precast is a construction product (mostly concrete) produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place. In contrast, standard concrete is poured into site-specific forms and cured on site.
The above clipping shows the construction of a house using precast structures.
Prefabrication is the practice of assembling components of a structure in a factory or other manufacturing site, and transporting complete assemblies or sub-assemblies to the construction site where the structure is to be located. The term is used to distinguish this process from the more conventional construction practice of transporting the basic materials to the construction site where all assembly is carried out.
The term prefabrication also applies to the manufacturing of things other than structures at a fixed site. It is frequently used when fabrication of a section of a machine or any movable structure is shifted from the main manufacturing site to another location, and the section is supplied assembled and ready to fit. It is not generally used to refer to electrical or electronic components of a machine, or mechanical parts such as pumps, gearboxes and compressors which are usually supplied as separate items, but to sections of the body of the machine which in the past were fabricated with the whole machine. Prefabricated parts of the body of the machine may be called 'sub-assemblies' to distinguish them from the other components.
The most widely used form of prefabrication in building and civil engineering is the use of prefabricated concrete and prefabricated steel sections in structures where a particular part or form is repeated many times. It can be difficult to construct the formwork required to mould concrete components on site, and delivering wet concrete to the site before it starts to set requires precise time management. Pouring concrete sections in a factory brings the advantages of being able to re-use moulds and the concrete can be mixed on the spot without having to be transported to and pumped wet on a congested construction site. Prefabricating steel sections reduces on-site cutting and welding costs as well as the associated hazards.
Modular Construction can be considered a form of Prefabricated Construction.
Still not clear? Try this piece of history
In early days of Ship construction (world war years), Ships were fabricated in the dry dock from scratch. The ships had to be constructed from base all the way up. This meant, thousands of construction workers working in close proximity with high rates of accidents and poor efficiency. Only after the bottom structures and the hull were constructed could the construction of the super structure begin. Below are a series of images of the construction of Liberty Ship Class. You can notice the sequences.
The images show the shortcomings of this method of construction. This is a type of Precast method where, the parts of ship (steel structures) are constructed elsewhere, brought to the dry dock and assembled. This meant the electrical wiring and hydraulics of the ship could not take place till the complete construction of the hull and structure. This would result in extended construction timelines.
Now, let us move on to the modern methods of Ship building. Case in point, The Gerald. R. Ford Class of Nuclear Powered Aircraft Carriers being built for the US Navy. They are using modular construction techniques. in other words, prefabrication techniques.
From the above pictures, you can take note of the fact that the construction is modular. Each module of the ship has been prefabricated at a Different location, transported and individual modules are assembled together. This has saved both costs and construction times.
Conclusion:
Precasting is a subset of Prefabrication. Prefabricated modules may contain precasted components. . . . not the vice versa...