Prefabrication is a construction method in which building parts are made in a factory before they are brought to the job site. These parts can include wall panels, floor sections, roof trusses, bathroom pods, and full room modules. The method matters because factories can control tools, materials, measurements, and weather conditions better than an open construction site.
This often makes projects faster, safer, and more consistent in quality.
Key Facts
- Prefabrication means making building components off site, then transporting and assembling them on site.
- Total project time can be estimated as Ttotal = Tfactory + Ttransport + Tassembly.
- If factory work and site preparation happen at the same time, schedule savings can be approximated by Tsaved = Tsite prep overlap.
- Dimensional tolerance is the allowed measurement error, such as length = 3.000 m ± 0.005 m.
- Crane lifting force must at least equal the module weight: F = mg.
- Productivity can be compared with rate = number of modules completed / time.
Vocabulary
- Prefabrication
- Prefabrication is the process of making construction parts in a factory before installing them at the building site.
- Module
- A module is a large prefabricated section of a building, such as a room or apartment unit, that is transported and connected to other sections.
- Tolerance
- Tolerance is the small allowed variation in a measurement that still lets parts fit and function correctly.
- Assembly
- Assembly is the process of joining prefabricated parts together at the construction site to form the final structure.
- Logistics
- Logistics is the planning of how materials, machines, workers, and prefabricated parts move through a project efficiently.
Common Mistakes to Avoid
- Assuming prefabrication means the whole building is made in one piece. Many projects use a mix of panels, modules, and site-built parts, so the construction plan must show which parts are prefabricated.
- Ignoring transport limits. A module that is too tall, wide, heavy, or fragile may not fit on roads, under bridges, or on available lifting equipment.
- Forgetting that factory accuracy depends on correct design data. If digital models or measurements are wrong, a precisely made component can still fail to fit on site.
- Counting only factory time when estimating the schedule. Transport, crane setup, inspections, utility connections, and site assembly all add time to the final project.
Practice Questions
- 1 A factory produces 6 wall panels per day. A building needs 48 panels. How many days of factory production are needed if the rate stays constant?
- 2 A prefabricated room module has a mass of 8000 kg. Using g = 9.8 m/s^2, what minimum lifting force must a crane provide to hold it steady?
- 3 A project can build walls on site in 20 days, or make wall panels in a factory in 12 days while the foundation is being prepared at the same time. Explain why the prefabricated method can shorten the project even if the wall panels still need transport and assembly.