This dissertation will discuss the effect of Modern Methods of Construction (MMC) and particularly the Off-Site Construction (OSC), on the building sector today, and how these methods will contribute to help and resolve social, financial, and environmental difficulties that facing the UK.
Off-site construction is an application of modern methods of construction MMC where building sector meets the industrial sector, or by other word, a fusion between building and manufacturing. Off-site construction is where any of building components, or even a whole building, manufactured in factories away from the actual site where the building will be sited, or simply is where the construction site is different from the building site.
Off-site construction has different terms, terms like (prefabrication, off-site assembly, factory assembly, pre-assembly, off-site manufacture, etc.). The term off-site construction is generally used nowadays to any part of the construction process that takes place in factories.
Off-site construction is not new, in the 20th century specifically in the post wartime, off-site construction (that time the term used probably was factory assembly or prefabrication construction) were needed to replace rapidly buildings which were destroyed or damaged during the war, But due to the lack of technology and modern production techniques, development in lightweights, high-strength materials, and new modern methods of construction that today is available, it gained unfortunately negative significance.
The time of the wheelbarrow is finished, “announced Jean Prouvé in 1947, echoing Le Corbusier.”We need usinées maisons”, homes produced in the factories
Since then, a further sixty years have passed: the manufacturing industry has come with story of success of the mechanization, has enhanced electronics and grafting. Today industrial automation and manufactures from shoes to personal computers, and from planes to crackers, all now “machine-made”, in Seattle as a small village in China.
The building construction is still the same. With very few exceptions, the building remains largely an object made by hand “with traditional techniques”. And the only construction industry still relies to logical and largely pre-industrial processes. With known effects: low productivity, forecast time and cost much more random, exposed to all levels of quality and possibilities and approximations of production conditions are vary widely, backward technologies and unskilled work.
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Why choose off-site construction now? What is so different from the traditional way of construction? Why is sustainability constantly being brought up? Before I examine these points, I have to mention some important facts that have already occurred. Since the beginning of the century, it is increasingly being talked about and discussed, the world and its climate changing. United Nations ask for action on it. The world met in a summit in Copenhagen to discuss how they can resolve the raising temperature that might cause damages and risks to the global, and how to reduce energy and CO2 emission. Why I mentioned climate change and we are talking about off-site construction? The answer is surprisingly, buildings are responsible for about one third of global energy consumption and if we add the energy used for construction the amount can easily be increased to the half. All of this means that we need to build very efficient houses and in an efficient way, and that’s can be achievable only by off-site construction.
There is a severe accommodation shortage in the UK. The Government has announced plans for the construction of 200,000 new houses per year, but that target has never achieved yet. Off-site construction can help the accommodation industry to achieve that target where fast delivery is needed. Speedier delivery in construction is one of the potential advantages of off-site construction and research showed that it can reduce the time of construction process to the half because it takes place in a desirable condition away from the unpredictable weather that can affect and delay the process on-site. And research showed that it can reduce the time of construction process to the half because it takes place in a desirable condition away from the unpredictable weather, factory built accommodation. Offsite construction already features in the production of social accommodation.elderly.jpg
Skill shortages in the UK construction industry are a severe problem. In 2001 the UK construction industry estimated it needed to train an extra 74,000 skilled workers every year for five years just to make up for the shortages of bricklayers, plumbers and electricians (Verbus System, 2006).
In 2009, the chartered institute of building (CIOB) concluded a third research on skill shortages, and the result again showed that the construction industry is still suffering a skills shortage, which is likely to continue to be a challenge for the building sector. Off-site construction can play an important role to resolve this issue. The research showed, compared to more traditional techniques, off-site construction can reduce on-site labour requirements to less than a quarter. This result achieved from some work took place off-site. Off-site work involves different labour that is not under pressure as the on-site workforce. Off-site construction and modern methods of construction (MMC) can therefore make better use of scarce labour.
1.5 DISSERTATION STRUCTURE
The dissertation consists of an introduction chapter, three main chapters and conclusion chapter; Chapter two discuss the advantages of off-site construction for the building sector, society, and the environment. The chapter also will discuss the conditions in order to gain the full advantages of off-site construction. Chapter three explain the types and forms of off-site construction, and where off-site construction takes place in the building and in the construction process. Off-site construction takes place in different areas of the building, so how off-site construction will incorporate with the mainstream construction process. Chapter four show and examine some of off-site construction case studies and in which type of building it takes place.
CHAPTER TWO: ADVANTAGES OF OFF-SITE CONSTRUCTION
Off-site construction, as I mentioned, is part of modern methods of construction (MMC) and is referred to as any of the components of the building built in a high quality controlled factories where they use advanced techniques to manufacture highly specialised doors, windows, stairs, wall panels, frame structure, and complete volumetric pods and then transport them to the location where it will be used and to be assembled on-site.
Off-site construction has many advantages that are why nowadays there are more companies and contractors using this method rather than the traditional way of construction, even governments make more pressure to use this method to speed up housing delivery.
Modern methods of construction can provide good quality homes with less on-site labour, in a shorter time, with at least the same building performance and at similar cost when compared to more established techniques.
Off-site manufacturing and partnering processes increasingly play a part in solving today’s problem of moving towards a sustainable housing industry.
The advantages of off-site construction can be classified into two types; Business advantages, social & environmental advantages
Modern construction methods can produce important benefits for housing authorities and developers, not the least of which is the reduced emphasis on on-site activity. This is particularly important in a time of increasing demands on an already stretched labour force. As with any new way of doing things there are risks, but these can be mitigated through good project planning and management (Sir John Bourn, head of the National Audit Office, 2005).
Less time in construction process, cost predictability, higher quality,helping the society and the environment, resolving skilled labour shortage, reduce health & safety risks,and helping the business & the economy. These are key advantages of off-site construction.
2.2.1 Reduced construction time
Business advantages give a huge encouragement to the contractors and designers to use more off-site construction components with their design and building processes. The greater speed of manufacturing and on-site assembling is an important factor for business gain. Earlier the delivery of the building means earlier the return of the investment. Modular construction for example, that is an off-site construction, is up to 40-60% quicker than traditional building methods. The predictability of the delivery also is very important for the financial calculation of the business in terms of cost and revenue. The manufacturing process of the components in quality controlled factories is nearly accurately estimated as well as the delivery to the site and the assembly operation.
2.2.2 Cost Predictability
Cost-effectiveness is an important factor to show the difference between the off-site construction method and the conventional one. Approximately, around 80% of the construction costs are fixed within the first 20% of the design process.
The graph below highlights the potential for cost reduction and alternatively the resistance to the cost of change during the project life. As the project progresses, the opportunities for implementing variation or change reduce and the consequent costs associated with these variations rise substantially, Where off-site production techniques are to be used, these should be introduced early in the process.
While off-site construction has tended in the past to be more expensive than brick & block, now is being reduced to the same level due to the innovation of more techniques and to the variety of the components, and these bringing even greater economies.
2.2.3 Superior Quality
Off-site manufacture for building components significantly improves the quality and the efficiency of the building due to high standard of quality control and test.
Buildings exceed requirements on sound and thermal insulation levels, so this means that are more sustainable.
2.2.4 Help the society and the environment
Off-site construction has also can help the society and the environment. Millions of affordable homes are required to meet growing demand, and there is increasing pressure to further improve efficiency and sustainability performance during construction and throughout the lifetime of the buildings.
Off-site construction is environmentally friendly if it is planned well from the early stages of design and by integrating all the supply chain together. Less energy is generally required to develop the modules or off-site manufactured components. With improved process control ,buildings are pre-engineered – each exactly the same and so can be adapted for ease of tiling and this should lead to reduced levels of waste on site of up to 70% and subsequent costs. In addition, with improved control of materials flow, raw materials can be recycled rather than ‘skipped’ as often happens on site.
The advantage of using OSC methods related to the reduction of waste to landfill are that the material usage in the factory is reduced up to 90% by the careful design and procurement of materials, reducing the amount of waste generated both on-site and off-site.
Offsite manufacturing was identified as a key potential method for promoting sustainability within the construction industry. Sustainability is increased as sound and thermal insulation are improved. Reduced time on site means less disruption to neighbouring residents or businesses.
2.2.5Reducing reliance on skilled labour
While there is a significant shortage of housing in the UK, and the government plans to build more accommodation houses, there is another problem facing to achieve these plans as well the building industry a whole which is the skills shortages bricklayers, plumbers and electricians. Off-site construction helps to build more houses by reducing reliance on increasingly scarce skilled labour by reducing the number of labour where semi-skilled factory labour can be used during the construction of modules.
2.2.6 Improve Health and safety
Health and safety issue also give off-site construction an advantage, it has been proven to be a safer method of construction because there are fewer components involved than traditional methods and there is no need for high quantity of labour on-site for the assembly process.
2.2.7 Business integration and economy development
Off-site construction helps to integrate the supply chain. When executed effectively, the off-site construction process involves key manufacturers and suppliers early in the feasibility and design stages of the project. This ensures that the specialist skills and knowledge of these key suppliers are embedded within the project and can influence the design and construction phases of the project. Where appropriate these key suppliers should be given ownership of the design and involved fully in the execution of delivery, storage and movements of materials and components.
CHAPTER THREE: OFF-SITE CONSTRUCTION! WHERE IT TAKES PLACE?
3.1Forms of off-site construction
Off-site construction can take a number of forms. The form and extent of acceptance within the projects will depend on:the type of project: ‘Is there a large proportion of duplication or replication?’ for example; in hotels and hostels, the type of client: ‘Is the client a one-off or repeat client?’, and the relationships and the arrangements between the project members.
Off-site buildings and components systems range from small bolt-together sections to virtually complete buildings.
Systems can be categorised as:
Panels (open or closed)
Sub-assemblies are the most traditional and widely used system in off-site manufacturing which is being used for many generations. Thistype of off-site construction can include elements using different type of materials such as concrete beams, block floors, and foundations.
Prefabricated foundation systems can consist of precast, post-tensioned, concrete beams.
Prefabricated beam installation in progress on piles. The beams can be omittedand modular structures can be installed to span directly onto piles and pile caps
Photograph courtesy of Van Elle
An additional examples for sub- assemblies systems are the glass reinforced plastic for chimneys, steel for curtain walling, and timber stairs.
Framed structures, which are pre-assembled in factories, supply the structural support to buildings and are not something new feature in construction. Lightweight pre-assembled frames which can be delivered promptly to the site, speeding up the construction times for the main structural elements. The benefit of pre-assembled framed structures, that can help of reducing site cutting and the inaccuracies that can arise from it.Untitled-1.jpg
Insulated steel frame building system Photograph courtesy of Fusion
An example of framed structure is the steel frame module.
Steel works in off-site construction are taking the most important part of the factory controlled construction due to the characteristics of the steel itself that can be shaped and moulded in any form; the result is light strong steel modules structures.
The UK construction market is one of the most steel intensive in the world, with steel proving to be the material of choice for UK architects and structural engineers in the multi-storey building market. The 2007 Market Shares Survey figures show steel construction consistently takes in excess of 70 per cent over double the market share compared to when the survey was first carried out in the early 1980s’.(Housebuilder& Developer. 2008).
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The Steel Construction Institute has carried out a study of different construction projects using various levels of off-site steel construction technologies in busy urban sites. The goal of the study was to recognize the benefits of off-site construction relating to the reduction of the disruption caused to local residents by the construction operations. The study also aimed to quantify these benefits in terms of the reduction in dust, noise, vehicle circulation and the impact of site-generated waste on the environment.
Panels are two dimensional frame that consist both the structural and the infill element, are sealed together on site. Example of panels are pre-assembled floor, wall, and roof panels. Using the right sealants are very important to gain the benefit of off-site manufactured panels in order to stand up the frames rapidly. The simplest form of off-site manufactured panel system is lightweight infill panels that are fixed to the structural frame, where the most complex form are the prefabricated sandwich panels which consist of both, the structural element, internal and external finishes.
3.1.4 Volumetric System
Volumetric system is the frame and panel systems, and when the building is assembled and built from a series of volumetric steel or timber modules, connected together to form a room or groups of rooms to form complete structure.
Modular construction is also a term used to refer the volumetric assemblies.
While the foundations are being prepared under factory conditions, the modules are manufactured and finished (or partially finished) off-site, under factory conditions, then transported to the building site and assembled and connected to the foundations, then added the exterior cladding and the roof.
Modular construction is more sustainable than traditional techniques because of the minimum foundations that required and because it is built under factory conditions, the modules are in better quality and defects are minimized.
Modular construction uses the same techniques from the industrial sector but the result does not look like “mass production product”. Sophisticated modules and panels can be produced and can be easily customised by the client’s requirements, and with new advanced techniques finishes: cladding and roofing, give the building its natural skin that suites the surrounding.
3.1.5 Hybrids System
Plant room is a room or space in a building dedicated to the mechanical and electrical equipments and then they need an intensive labour. If plant rooms built off-site where there is cheaper labour, this can be more economically. Other advantage of plant rooms built in factory is if a project in time difficulties, always the installation of the services is squeezed, so using modular plant rooms certainly will help to avoid this problem.
Using system-engineering principles, the resulting prototype has been developed principally for use in the construction of two and seven storey residential developments. It is a hybrid of frame and infill panels, the prototype enables construction in stick form, panels or 3D volumetric units, and works on the principle of a frame and infill system. The mainframe is hot-rolled steel and typically uses regular or square hollow sections with a width of 100mm for both columns and beams to provide a standard interface that can be in filled with floor and non-load bearing wall panels to complete the building.
The prototype is based on currently available main components, which can be connected in a variety of ways to suit the individual project to allow flexibility in the level of work carried out off-site. Connections include innovative bolt connections to allow complete demountability, location systems and welded connections, all of which can be used in isolation or as part of a combined system.
Bathroom construction process can use Off-site construction technology, which in compare to the traditional way, would normally be carried out on-site. If we remove the construction process of the bathrooms to a controlled factory environment, bathrooms will become more ecological, functional, and with lower building costs. Bathrooms that we call them ‘smart’ will also become more common with highly environmentally toilets and showers systems and with more advanced technology like tapes with sensors. The quality of bathrooms pods is far superior to the traditional on-site construction, more stylish, with high quality materials, and better for the environment in terms of a lower carbon footprint, lower levels of waste and reduced transportation of components.
Bathroom pods are a very economically solution when it integrate with the whole construction process in large quantities such as; student accommodations, hotels, hostels, hospitals, and prisons.3.jpg
CHAPTER FOUR: CASE STUDIES
4.1 British Land Ropemaker site, London
Ropemaker is a commercial building for British Land, one of the UK’s largest Real Estate Investment Trust. It is built in an eminent site in London. The 21 storey and three basement levels has 55,000 square metres net lettable space. The high profile building has impressive green certifications achievement including a BREEAM ‘excellent’ rating.
The development has been realised using off-site construction technologies in a large number of parts in the building.
This study aimed to evaluate two products manufactured off-site; a modular walling system “Podwall” from “Swift Horseman”, and “Technik” flooring system supplied by “Grants LTD”.
The research aimed to compare in deep analysis off-site construction techniques products to the traditional way of construction in terms of; waste on-site and off-site, resources needed on site, efficiency and productivity, cost, environmental impact analysis and end of life assessment, health and safety, and installation time.
Features of the Podwall system (Swift Horsman. 2010)
A flexible modular walling system incorporating finishes and services.
All elements manufactured off site in a controlled environment.
Innovative fit out solution providing high quality female, male, and disabled toilet units throughout the development.
PODWALL research results
Performance breakdown (man hours on site)
Podwall saved approximately 40% to programme. Each floor at Ropemaker had an 11 week programme to install the Podwall (3 blocks per floor – one ladies, one gentlemen and one disabled toilet), which would be equivalent to 15½ weeks for traditional fit out.
Because the Podwall is manufactured off-site the waste on site is reduced. The largest proportion of waste generated is in the packaging, which ensures the product is protected between factory and site.
Across the Ropemaker site a total of approximately 213m3 of waste was produced for all Podwall washrooms. Given the low levels of waste observed during the monitoring of the Podwall, traditional waste would considerably exceed the Podwall waste volumes.
The percentage of materials recycled from Ropemaker frequently exceeds 85%.
At Ropemaker the Podwall washroom package has a value of approximately £6m, with 54 toilet blocks being delivered across 1969m2 The main differences in cost between the Podwall and the traditional system are in services installation and cubicles. This is because services are integrated off site into the walls and cubicles for the Podwall which explains the greater cost of these elements, whereas with traditional build the cost of installing services on site is higher. The traditional costs do not account for
indirect costs such as the increased cost of waste and removal thereof and the increased programme time to install the traditional product.
4.2 Case Study: Bewdley High School and Sixth Form, Worcestershire
This case study involves a school and sixth form building based in Bewdley, Worcestershire. A new building which can meet the needs and expectations of this school is to be proposed, designed and implemented. The requirements are said to be a building which offers flexibility for the school and its occupiers as well as being a low-energy solution. The changing needs of the school means space needs to be provided to accommodate the new influx of around 360 pupils.
‘Yorkon’ manufacturers, who are based in the city of York, have created a two-storey high building at their off-site location. Due to the nature of the build taking place away at York as an ‘off-site’ project, the building only took a mere 22 weeks to put together compared to an on-site project which would take longer. This new building has become a project now boasting a title as not only one of the most sustainable modular buildings within the UK, but offers heating via biomass fuel and holds a complex passive and low energy ventilation system. The building comprises of 60 steel-framed modules and has clear internal spans measuring up to 12m for space planning flexibility within. The parts were brought in using cranes and windows and partitions were put into place. The effectiveness of pre-installing the windows and partitions off-site show the efficiency and speed of this new phenomenon.
It is a desired and sought after concept to still incorporate off-site construction into the regular and more traditional building techniques. The fact the building has integrated off-site technology into its production whilst still being themed around a conventional and traditional design for a drama and dance studio, ultimately shows the two somewhat diverse approaches to construction working in harmony together.
The building comprises a 12 classroom facility which may accommodate the schools Modern Languages, Humanities as well as English Departments. Furthermore, a designated creative-area is also catered for within the design concept as well as an area for an administrative centre. Its design features boast central-heating fuelled by biomass fuel thus being environmentally friendly by minimising harmful carbon emissions. Not only this, but the new building can offer all timber cladding from sources that are confirmed sustainable, a highly-glazed activity studio offering a plentiful amount of natural light and an appealing bespoke roof structure that’s pleasing to the eye.
Looking further into the building’s design concept in offering a complex passive ventilation system, we can see that the clever idea of well-ventilated rooms provide a more comforting area for study and teaching. This additional air-flow is thus providing better concentration and performance for all those working within the new building. This is achieved through something recognised as ‘passive air-stacking’. The sensors installed are there to monitor levels of both carbon dioxide as well as temperature. This enables fresher air to be drawn in accordingly when detected as too low. This is fed diagonally over radiators which prevent the possibility of unwelcome cold draughts. Any stale air from the room is passed out from the room via high capacity discharge terminals found on the roof. This ultimately creates a continuous regulation of new air flow replacing older air providing optimum air composition levels in each room.
Professionals working at Yorkon have expressed their views in using off-site construction in this project amongst others. They voiced that the main decision to go for off-site production was speed in completing the project which was highly important in making sure the facility would be ready on time for the new quantity of pupils to be joining the school. Furthermore, Yorkon is keen to be recognised as a reputable name in supplying superior quality along with an eye for sophisticated and precise detail in the designs and bringing revolutionary new techniques to building which can change attitudes towards regular modular construction. This is all despite any challenging timescale. Yorkonis adamant their team has provided the required building which can boast quality, bespoke elements and flexibility along with highly favoured low energy, environmentally friendly and speedy results.
(The new building has provided us with spacious accommodation and room sizes that are appropriate for our learning and teaching needs. It is visually pleasing from the outside and fits in well with the locality. Our students have been impressed with the design of the building and it has helped to develop a strong sense of pride in our school and working environment.
The modular approach is a very good method of construction for schools as it limits the disruption to learning because of the speed of assembly. The building will be easy to expand and the design is sufficiently flexible to meet the changing needs of our students and curriculum development.-Julie Reilly, Head Teacher and Sixth Form centre.)
4.3 Case Study-Emergency Assessment Unit, University Hospital of North Tees.
In this case study we are looking at the new revolutionary building which was designed to fulfil the needs of Interserve Project Services/North Tees and Hartlepool NHS Foundation Trust. The building will be located at the University Hospital of North Tees. The purpose-designed and built Emergency Assessment Unit has been required in order to reduce waiting times for much demanded emergency treatment. This is something the Government has planned as to drive down waiting times for patients. The amount of beds are needed to be increased at the Stockton site as well as the site needing to be able to provide a service to those needing emergency surgical care, based centrally on location rather than some distance away. The unit has promised to feature up-to-date emergency care and include specialist staff who can deal quickly and efficiently with a high number of patients thus increasing patient turnover.
The solution to these needs was met through a £2.8m Procure 21 project which was awarded to Yorkon manufacturers, based in York, by Interserve Project Services. Off-site construction and the installing of a 42-bed Emergency Assessment Unit was the aim for the new building as its production. The building included 42 steel-framed modules manufactured off-site at York and installed on-site in as little as a few days. Disruption was therefore limited and patients could rest unaware of any commotion. The 1,710m square single storey extension to the pre-existing department was astonishingly and impressively erected in just over six months from beginning to end. The building also can boast a full range of modern well-equipped facilities for any acute medical emergencies.
Features are listed as including four-bed wards, single en-suite bedrooms, an isolation ward, high-dependency beds, consulting rooms, ward manager’s office, waiting area, Quiet room, staff changing facilities and rest room and also an interview room.
Incorporated into the design were roof lights to increase any natural light in the centre of the unit and furthermore holds latest technology equipment. The installation of workstations are readily available and can be used at a patient’s bedside. This building proudly boasts to be one of the first unit’s in the country to offer an electronic information board too.
Looking to the comments of professionals working within the construction of this new high-tech building, we can see the positive influence of off-site technology in providing rapid, quality solutions to much needy clients
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