Modern Methods of Construction

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.

1.2 DEFINITION

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.

1.3 TERMINOLOGY

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.

1.3 HISTORY

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 Prouv’ in 1947, echoing Le Corbusier.’We need usin’es 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.

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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.

1.4 OVERVIEW

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.

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

2.1 INTRODUCTION

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).

2.2 ADVANTAGES

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 is improved. Reduced time on site means less disruption to neighbouring residents or businesses.

2.2.5 Reducing 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?

3.1 Forms 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:

• ‘ Sub-assemblies
• ‘ Frames
• ‘ Panels (open or closed)
• ‘ Volumetric system
• ‘ Hybrids system

3.1.1 Sub-assemblies

Sub-assemblies are the most traditional and widely used system in off-site manufacturing which is being used for many generations. This type 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.

An additional examples for sub- assemblies systems are the glass reinforced plastic for chimneys, steel for curtain walling, and timber stairs.

3.1.2 Frames

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 can help of reducing site cutting and the inaccuracies that can arise from it.

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).

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.

3.1.3 Panels

Panels are two dimensional frames that contain both the structural and the infill element, are sealed together on site. Example of panels is 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.

An example of volumetric module structure is bathroom pods. 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.

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.

3.1.5 Hybrids System

Hybrid systems (often referred to as ‘semi-volumetric’) are a combination of all the other type, and this type where the flexibility of production and the varieties of consumer choice by combining the best features in a single system play the important role of it.

Plant rooms is an example of a hybrid volumetric module manufacturing

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.

CHAPTER FOUR: CASE STUDIES

4.1 Case Study: 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 Horsman’, 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.

PODWALL research results

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 15′ weeks for traditional fit out.

The waste on site is reduced because the Podwall is manufactured off-site. The result showed that the largest amount of waste generated is from the packaging, which is very important to protect the product on the delivery from between factory and site.

Total waste produced is approximately 213m3 from Podwall washrooms. If we give the low levels of waste monitored during the process of the Podwall erection, traditional waste would considerably exceed that figure. In terms of waste recycling the percentage of materials recycled from Ropemaker exceeds 85%.

The Podwall washroom package (54 toilet blocks), which is delivered over 1969m2, has a value of approximately ‘6m. The main differences in cost, that the services are integrated off site into the walls and cubicles for the Podwall, while in the traditional system the services installation and cubicles must be installed on-site and the cost of the installation of these services on site is higher. The indirect costs in the traditional way do not count as the increased cost of waste and removal, and the increased programme time to install.

TECHNIK research results

In terms of performance and time, Technik flooring system took168hrs per 100m2 for the pedestal and the floor, while in screeded floor take 250hrs per 100m2 for the insulation, screed, and tiling. Tiling is the most labour intensive element of traditional flooring, and drying time for screed increases programme and risk of damage when wet.

The result showed that 32% of time spent laying a traditional floor was non value added time compared with 17% for Technik floor. Technik’s 83% added value time demonstrates the efficiency of off-site flooring as well as the reduction in remedial work (WRAP. 2009)

At the factory 0.49m3 of waste is generated raising the total waste to 2.81m3 per 100m2. The total waste of Technik flooring of Ropemaker is 24.56m3. While a total 41m3 of waste if screeded floor with tiling had been used on site instead. The screeded floor generates a significantly greater amount of waste compared to the Technik floor.

In terms of costs, Technik flooring labour costs was ’84/m2, while the screed floor was ‘114/ m2. Material costs were ‘140/ m2 for Technik floor, and ‘147/ m2 for the traditional one. These figures are near, but it is still considerable that Technik is cheaper if we put in consideration that drying time for screed increases programme and risk of damage when wet and the materials associated with the traditional screed design take up a greater area within a warehouse and as such the cost is considerably higher to that of Technik floor. A programme/time saving of 25.7% is made by using Technik flooring, which clearly has a cost saving implication as well. (WRAP. 2009)

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 installations 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. The accuracy as well as speed of construction has impressed many working on the project. The patients are the first top benefit thus impacting greatly on society. A faster completion has resulted in an earlier date for increasing the hospital’s capacity and implementing the hospital’s new care programme. The building has proudly been created free of any defect and furthermore feels and appears like a building created in the traditional on-site method. The impact on the people within the building can be felt as they feel secure and at ease with their impressive new surroundings. After significant planning, the result proves to be pleasing and satisfying to all those involved. Impressive design features are said to include isolation rooms, en-suite bathrooms, no touch taps as well as bespoke window blinds, all that was promised. All in all, a roomy and calm working environment which is properly equipped to looking after those that need it has been established.

4.4 The Steel Construction Institute (SCI) Case Study

The Steel Construction Institute (SCI) Study, which was funded by The Department of Trade and Industries (DTI) with support from Corus Strip Products (UK), is started by visits to six construction sites where oft-site construction technologies were being used for data-gathering. A comparative study had been made and followed by the visits to compare the traditional way of construction to off-site construction methods for a 2-storey school where light steel infill panels were used in off-site method against the traditional method, and a 4-storey light steel residential building where off-site modular construction were used against traditional masonry way. The study results showed that off-site construction is by far reducing the disruption to the local residents

The growing demand for residential housing in cities, towns, and villages of the UK and the scarcity of so-called ‘green field’ sites, is forcing developers to build on small plots of land within existing residential developments. As housing is built, so the demand for schools, shops, hospitals and leisure also increases.

Construction on confined urban sites presents developers with various challenges including:

The construction of urban sites contained presents developers with a number of challenges, such as; the lack of working and storage space, the absolute necessary to minimize the impact of all aspects of construction on local residents, and the scarcity of skilled labour working in construction sites.

Last Recent experience with modern construction methods showed that these challenges can be met by changing some of the activities of site-intensive products with components manufactured off-site. For example, panels of three two-dimensional and three dimensional modules are supplied in very short time to local conditions and require no storage space on site.

Regarding urban disruption, there is some non official evidence to suggest that the disruption to the local residents and inconvenience caused by construction can be greatly reduced by the use of prefabricated lightweight steel and modular solutions. Such methods do not only transfer much of the construction processes off site, but They also significantly reduces the construction time, thereby limiting the inconvenience Caused by site traffic, deliveries, waste clearance and general construction activities.

One of the greatest opportunities and challenges for the steel sector is the residential market due to the increase awareness of the physical benefits of steel. As often, home builders and developers are looking at things more closely as the project predictability and speed of construction, and areas that can generate financial returns earlier. Construction in steel, which has always been a technique of off-site construction, is the solution.

With its speed of construction, cost-effectiveness, outstanding performance, and unparalleled sustainable qualities, steels off-site construction techniques provides a genuine opportunity for the construction industry to meet growing, and sometimes conflicting demands, in providing affordable housing in today’s difficult housing market

By its very nature, steel based off-site construction gives rise to more predictable construction programmes, along with predictable cost, construction quality, programme timing and project handover with faster lead in and onsite project commencement, allowing earlier use and business income return. Ultimately, this can result in the overall construction programme being reduced by up to 60 per cent compared with conventionally constructed buildings.

CHAPTER FIVE :CONCLUSION

To conclude, a survey undertaken by Contract Journal revealed interesting findings. Although the survey results indicated that off-site construction is on the rise and gaining popularity, the rise is still lower than the desired figures the industry would have liked to have seen. The survey