‘’Aim to build as much of the building under cover out of the rain’’
Anthony H 1945 Houses, permanence and prefabrication
During the industrial revolution Victorian engineers could not have made it possible to build structures such as The Britannia Bridge with out prefabrication. Although the components were not constructed in factories originally they were made in safe places.
Even the best-organised building sites are full of problems, whether it be weather, material or employees and can slow the process of building down.
Off-site prefabrication is one of many innovative ways used in the construction industry to developers seeking cheaper construction. Prefabrication of buildings has advantages such as function of the building, quality, time, builder’s safety, quieter construction and less disruption of surrounding dwellings and more efficient labour, these will be explained later on.
Pre-fabrication is essentially building all the components needed to erect a building or full modular rooms made offsite in a factory. Any type of building from a shell or pod to a multi story building with prepared openings for all utilities, windows and doors.
This method has been used since ancient times. it is said to be the world’s oldest known engineered roadway, the sweet track constructed in England around 3800 bc, used prefabricated timber sections that were bought to the site rather than assembled on-site.
During the mid-nineteenth century using timbre to construct a ‘portable’ hospital with wall panels in galvanized sheeting, a manufacturer called Charles D. Young & co undertook the contract to provide iron barracks for a two storey 200 hundred patient hospital. These are a couple of examples of how pre-fabrication was and can be compared to how it has evolved today.
Prefabrication was heavily used in construction in the UK during the 20th century due to houses in the UK needing to be rebuilt from bombing during the Second World War. Assembling sections in factories saved time on-site and reduced costs. Unfortunately the quality was poor, and when prefabricated housing was used for longer than its intended life, it acquired a certain Stigma.
More recently prefabrication has been successfully used for the construction of hospitals, hotels and schools in the UK as well as for housing in other countries. This helps to provide the assurance of building methods and materials that have been tried and tested in use. Whilst quicker build times are the ultimate goal, they are not achieved at the sacrifice of quality of design and workmanship.
The most common-used form of prefabrication in the building industry is the use of prefabricated concrete and prefabricated steel sections in structures where a certain part or form is repeated many times. It is very hard to construct the formwork required to mould concrete components on site, and delivering wet concrete to the site before it begins to set requires perfectly accurate 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.
Used in the construction apartment buildings, and housing developments. Quality prefabricated units had increased to the point that they may not be discernable from traditionally built units to those that live in them. This technique is also used for office blocks, warehouses and facotrys. Prefabricated steel and glass sections are widely for the eterior of large buildings.
Site construction requires the use of outside architects, engineers, and general contractors. multiple contracts will be required for various phases of the work very often, this increases the owner’s administrative workload.
Now there is an alternative. Modular prefabricated buildings of practically unlimited sizes are available on the market. In addition to not limiting the size of the shelter based on shipping constraints, a modular prefabricated building offers three clear advantages over site-built construction:
Shorter construction schedules. Construction schedules are improved by simultaneous construction of foundations, associated site work, and the modular prefabricated buildings. A shelter can be manufactured at the same the other components are fabricated, and will be on hand for immediate installation.
Weather and labour problems can be averted, as they do not affect the modular shelter being built in a sheltered factory. Thus, you shun costly delays and can generate revenues faster.
Lower costs. Since prefabricated modular shelters are not subject to regionally high construction costs, installation costs may be lower as well. Material and labor costs do not increase when shelters are located in areas where labor and materials are more costly.
Larger manufacturers of prefabricated modular buildings should be able to provide complete architectural and engineering services. This includes preparation of permit drawings sealed by a registered engineer, and assistance in zoning or permit hearings.
Less contracts for the owner to administer. Any larger site-built buildings will require multiple contracts. Site-work structure erection, roofing, plumbing, HVAC, and electrical construction will all require different sub-contractors and different contracts. By ordering a modular prefabricated building, the owner can eliminate the need for all subcontracts. Bigger manufacturers also can organize site work, foundation construction, building, offloading, and setup.
There are however a few disadvantages. All pre-fabricated components whether steel, glass or concrete must be handled with the utmost care as not to damage them. Attention has to be paid to the strength and corrosion-resistance of the joining of prefabricated sections to avoid failure of the join. Similarly, leaks can form at joints in prefabricated components. Transportation costs may be higher for large prefabricated sections than for the materials of which they are made, which can often be packed more efficiently. Large prefabricated sections require heavy-duty cranes and precision measurement and handling to place in position.
To sum up, off-site manufacturing utilizing technically advanced prefabrication processes for improvement of build quality and efficiency with mounting importance to increase both number of houses built and the efficiency with which they are built. Modern methods of construction have never been more relevant.
thanks to http://general-learning-centre.blogspot.com