The main objective of this report is to elaborate on the advantages of using modular units in the construction industry, the improvements in the construction principles and the development in the materials used.
The purpose of the study
Modular construction, combined with the use of BIM, provides an effective technique to reduce overall waste on a project, providing a more environmentally sustainable building solution and creating a healthier and safer environment.
This report is mainly based on literature review and serves as a foundation for the author's future research into other areas of construction.
CHAPTER 1 - INTRODUCTION
Figure : Modular residential homeFor many years, buildings have always been built on-site. Great structures have been built and a development of craftsmanship. As compared to other industries, the building industry lags behind in the way it provides its products. Building costs have greatly risen due to the complexity of the building techniques and equipment used and the high labour costs and scarcity of skilled workers. There is a struggle to improve quality, labour costs, material usage and the times spent for constructing buildings and this is leading to new and innovative methods being implemented. Prefabrication or modularisation is one method which is being highly valued as a driver for the improvements in the production and efficiency of the building industry. http://www.boxliving.co.nz/images/slideshow/sitewide/Box_Muriwai.jpg
Definitions:
Prefabrication encompasses the construction of all building components that are a part of a larger final assembly. It is an off-site manufacturing process that takes place at a specialised facility in which various materials and building systems are joined to form a component or part of a larger final installation (Schoenborn, 2012).
Modularisation refers to a process of breaking a complete building down into a series of smaller modules constructed off-site so the on-site construction is reduced to foundation work and modular assembly (Schoenborn, 2012).
Modular is a term that is of, relating to, or based on a module or modulus or designed with standardised units or dimensions, as for easy assembly and repair or flexible arrangement and use. [1] These terms will be used interchangeably throughout this report.
Modular units in the construction industry have been incorporated to address quality and time or managing costs. In recent years, as the climate change escalates, a question has arisen on how the construction industry impacts the environment. There are climate changes that need to be addressed by all industries and this is leading the construction industry to find ways on addressing the changes.
It is noticeable that other industries have greatly improved the way they provide products, they are more leaner, more time and material efficient, and more worker friendly. The construction industry needs to improve the way it delivers its products to meet the requirements of design, cost and time. John Fernandez writes, "It is widely believed that construction is the slowest of all industries of such scale in implementing proven, scientifically sound technological innovation." [2]
In order for the construction industry to attain higher efficiency and precision, environmental consciousness, making a better use of a declining workforce, and providing shorter construction cycles, there is increasing use of modularisation throughout the industry.
The use of modular units in the industry to provide permanent structures is being received by the public as a means of attaining quality, cost and resource efficient and shorter times for the construction. There is still need for a paradigm shift away from the conventional or on-site building as people associate modular units with compromised standards, cheap materials and temporary structures which is not the case.
Figure : B2 tower by ShoP Architects proposed to be the largest prefabricated modular structure to be erected.Modularisation is getting up-to-date with design trends, building demands and market influences meeting today's construction demand with transformed styles and options. Modular houses are being designed and built with the styles, architecture and details similar to on-site built houses.http://static.worldarchitecturenews.com/project/uploaded_files/18183_SHoP_Atlantic%20Yards%20B234_cgi_B2%20at%20Flatbush%20Avenue%20and%20Dean%20Street.jpg
Modularisation has started branching into multi-family housings constructed in factories and assembled on-site. Quality and design are continuously improving, making modular buildings more structurally comparable to on-site buildings.
Modularisation is most likely the future for the construction industry and this will place the industry up-to-date.
CHAPTER 2 - HISTORY
Modular construction is often considered the future of the building industry. It has been in use for over a century. An early example of modular construction use can be found in Britain's Great Exhibition of 1851, featuring a building called the Crystal Palace. It was designed in less than two weeks using light and cheap materials: iron, wood and glass. The construction period lasted only a few months and consisted of assembling the prefabricated components. After the exhibition, the palace was taken apart, piece by piece and moved to another location.
Figure : Quonset huts in front of Laguna Peak, Point Mugu, in 1946Modularization was increasingly used during World War II due to the need for mass accommodation for military personnel. The USA used Quonset huts as military buildings which were made of steel structures of 5m by 11m and 2.4m radius. The sides were corrugated steel sheets with plywood.http://upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Quonset.jpg/250px-Quonset.jpg
Following World War II, there was need to rebuild and prefabrication and off-site construction was implemented to fill the demand. Since then, there have been great improvements in modular construction techniques.
"Recent innovations over the past few decades have allowed the prefabrication and modular construction industry to make significant advances in developing processes and materials to build and deliver more sophisticated and complex facility types" [3] .
A current example of how well accepted modular units have become is their use in the construction of the Queen Mary II cruise liner which is one of the largest and most expensive cruise liner in the world. The use of modular units is becoming more widely recognised as a resource efficient and greener construction process. [4]
The advanced technology has increased what modular construction can achieve in the construction industry. Here we can see that the introduction of cranes that can lift heavy loads of up to 100 tonnes have greatly increased in sophistication. BIM, quality modern materials and sophisticated manufacturing facilities now offer significant productivity gains on projects not possible before.
As the construction industry faces a shortage in on-site skilled labour and the need to adopt lean production methods, many believe the time is right now, more than ever, for widespread adoption of off-site prefabrication solutions on a major scale in the construction industry.
CHAPTER 3 - ADVANTAGES AND DISADVANTAGES
Advantages of modular construction
Construction Time Reduction:
Using modular units allows for the building and the site work to be finished simultaneously. This is achieved as both site works and prefabrication take place at different locations which reduces the time needed to complete construction by as much as 50-60% as compared to the on-site construction, leading to an earlier return on investment and saving in preliminaries. Saving time may also be achieved by way of employing lean production techniques. This means that there are no delays as may often be the case with on-site built construction.
Better quality Construction:
Because modular units are built in factories, manufacturers are able to utilize tools unavailable to the site builders such as custom manufactured jigs which ensure that all walls, floors and ceilings are square and plumb. In addition, interior walls are lag-bolted to the exterior walls and bracing and insulation are installed on all electrical outlet boxes. Finally, straps brace the wall to the floor. This is achieved by factory based quality control and pre-design of similar modules.
Light weight structures:
Compared to site construction, modular construction is about 30% of the weight of conventional masonry construction. This allows for easy mounting and quick and easy reuse in case of relocation.
Design Flexibility
Modular construction allows for a number of options and design possibilities that suit a client's needs. A wide range of plans and styles can be generated and in regards to the building regulations, a client can upgrade the general construction specifications allowing for endless possibilities.
Economy of scale
Repetition of modular units' production leads to considerable economy of scale in production. Modular buildings can save the clients as much as 20% on modular building projects as compared to conventional construction projects.
Requirements for highly skilled labour onsite are minimal, an advantage in areas where skilled labour is either costly or unavailable.
Procurement is often simplified, especially when the installation site is located in an area where raw materials and equipment are expensive or difficult to obtain.
In addition, modular construction can shorten schedules by allowing for concurrent processes, such as fabrication, permitting and logistical arrangements.
Cost overruns are virtually non-existent in the modular industry as climate controlled factories ensure that there are no weather related construction delays.
Finally, because of the large quantity of modules to be built, the factories save on the large purchases of materials and yearly buying contracts with suppliers.
Inspection and Regulation
Before modular units are manufactured in a factory, all building plans are reviewed by the local authorities of the location in which the buildings are to be finally shipped. Manufacturers as well contract a third party agency that conducts plan review on behalf of the local authority to perform an in plant inspection where labels are placed on the modules certifying that the modules have been manufactured in conformance with the approved plans and complies with all of the building regulations.
Environmentally friendly
Modular construction is more environmentally friendly than on site building. Here engineered construction materials are utilized and effective in-plant recycling is in place at most modular construction manufacturing facilities. This means that all the excess materials are able to be recycled. There is as well less disruption on site for installation placements.
Use on infill siteshttp://assets.inhabitat.com/wp-content/blogs.dir/1/files/2012/01/Polikatoikea-Filipe-Magalhaes-and-Ana-Luisa-Soares-1-537x357.jpg
Figure : Polikatoikea by Filipe Magalhaes Urban in fill competition.Modular boxes are useful in small urban and infill sites and in roof-top extensions to buildings as they minimize lay-down space. Under-utilized pieces of land in existing developed areas can be utilized using modular buildings allowing for a diversity of houses and improving the compatibility between existing and new developments.
Safer construction
Modular construction sites have proved to be significantly safer than traditional on-site building. Since the modules are built in a factory, and all materials are stored indoors in a controlled environment, there is no risk of mould, mildew, rust, and sun damage that can often lead to serious respiratory problems.
Reduced site labour requirement
The erection and finishing teams, which install and complete modular boxes, involve fewer workers on site than traditional buildings and this minimizes the project's impact on the customer site.
Skilled Subcontractors
One of the problems of today's site builders is finding skilled subcontractors. Because modular buildings are built in a factory, the subcontractors are already there and here skilled craftsmen construct each building to exact specifications. In addition, brand name building products that are trusted and known are used.
Reduced professional fees
Standardised design details for modular buildings simplify and reduce the need for specialist design input.
Services and bathrooms
Service modules can be used; these result in fewer fitting errors and re-work because components can be pre-fit prior to shipment.
Disadvantages of modular construction
Hidden Costs
Although prefabrication is cheaper due to time and labour savings, which can be substantial, the hidden costs in prefabrication may include:
Overheads: Manufacturing facilities employ full-time staff and have facility costs such as equipment purchase and maintenance, renting space, and monthly utilities;
Profit: Offsite fabricators, as a business enterprise, must make a profit and therefore to cover these overhead expenses may charge as much or more than a general contractor for the same scope and any savings due to efficiencies in time and labour may not be passed on to the customer;
Transport: Transportation due to prefabrication is higher per unit volume because of the chunking of the panels, modules, and components that are often shipped with more air than tightly packaged, onsite-erected materials and products;
Setting: Although weight is usually not as much of a concern, craning a prefabricated element can be awkward and require skilled labourers or dedicated crews to set the elements;
Design fees: As prefabrication requires more coordination with construction and fabrication teams, architects and engineers may charge higher rates for the investment of time.
Volumetric:
Transporting the completed modular building sections take up a lot of space. This is balanced with the speed of construction once arrived on site.
Flexibility:
Due to transport and sometimes manufacturing restrictions, module sizes can be limited, affecting room sizes. Panelised forms and flat pack versions can provide easier shipment, and most manufacturers have flexibility in their processes to cope with the majority of size requirements.
CHAPTER 4 - CONSTRUCTION PROCESS
Introduction
Figure : Factory built modular Architecture.Modular units are manufactured indoors under a controlled environment on assembly lines. Here independent building inspectors are on site to supervise the construction and ensure that the company adheres to all building regulations during assembly. Modular construction may take as little as ten days but more often one to three months. Completed modules are then transported to the building site and assembled by a crane. Placement of the modules may take from several hours to several days. Once assembled, modular buildings are essentially indistinguishable from typical site-built structures. http://www.modularclassrooms.org/wp-content/uploads/2012/06/factory-built-modular-architecture.jpg
The modular construction process is different from the conventional method as it is incorporating practices such as improved management, efficient materials procurement and streamlined production practices. These practises minimise the total amount of construction waste, time spent and improve on the productivity of the building industry.
Modular construction uses frame construction systems were steel or timber frame structures are used on which building components are connected and this influences the design and form of the building concerned.
Elements
Buildings can be created out of linear, planar or spatial elements and these determine the characteristics of the system building: the frame, the panel and the room module.
planar
linear
spatial
Figure : Building element systems
Modular building systems
Steel Frame systems
Steel frames are widely used in a variety of building forms. Columns and beams are made of steel and create a frame of linear members with minimal weight that has load bearing capacity and allows large spans between columns. The elements span between 6 and 18m as the most economical span.
Loads are transferred to the foundations via beams and columns and bracing elements ensure the stability of the construction horizontally and vertically.
The steel elements can be rolled steel elements, hollow steel sections or composite elements.
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Modular units mainly use steel frames which are either made of hollow tubes or rolled steel.
Timber frame system
Connection techniques
Depending on the building element and its functions, the connection of the material differs. In steel there are fixed and demountable connections. Here bolts, rivets and welds are typical connectors.
Fixed connections
Rivets:
Rivets have a high aesthetic quality when used but the method is both labour intensive and uneconomical. Nowadays riveting is being used when repairing listed or protected buildings or for repair work to riveted historical constructions.
Figure : Rivet connection processThe installation process: A the rivet is heated, descaled with a wire brush and placed in the rivet hole. The required pressure is provided by the rivet hammer, or rivet gun to produce a second head. Cooling then occurs to allow expansion forming a tight joint. [5]
Welding
Steel elements are welded using electric arc-welding or gas-welding. These can be hand or automatic welding and all elements must be adjusted prior to welding.
Figure 8: Metal Inert Gas Welding
Welding is usually used in connecting the steel elements e.g. steel trusses to achieve the required lengths and also when assembling the units. The modular units are usually welded to the foundation.
Demountable connections
Figure 9: Welded componentBolts
Bolted connections are the mostly used demountable connections in the building industry because they allow building elements to be exchanged and the construction to be dismantled at a later date. Frame constructions are also erected in short periods of time. These bolts are mainly used for the structural connections of the building elements i.e. beam to column connections. Since bolts are left exposed, during the design process careful consideration must be taken to ensure their safety.
Design Stage
Before the fabrication of the modular units, engineers and architects evaluate the building systems to be used determining their impact on the design and cost. Evaluations and recommendations in regards to the building systems, materials, equipment and improvements are proposed identifying how to reduce cost. Modular designers always consider market research, product development; production and sales in order to achieve their targets. The production process would always depend on the client's needs.
Van Gassel (2006) suggested that three design tools are usually developed while design modular constructions and these are:
An object tree: a structure description and detailed explanation of the system. This schematically presents the interrelationship of all building parts and shows where the parts will be assembled.
A guideline: a four step system analysis approach.
Input - the limitations that the final product must bear in mind
Process - the elaboration of all input parameters
Output - the changed product model
Evaluation - a check is performed to confirm whether the output model takes all limitations into account
A ranking system: definition of the decision of the decision-making criteria and of the qualitative levels, presented as a coloured filter. If the evaluation is positive, it will be necessary to determine whether the output model also takes into account the limitations identified in the previous steps. If this check is positive as well, the product continues to the next step. If the product fails one of the checks, it has to be modified as part of t the current step or by going back to an earlier stage of the process and continuing from there.
Assembly Stage
Fabrication factories are usually designed in two basic flow patterns. In side-saddle flow factories, the modules move through sideways in a single line whereas in Contrast, modules are arranged end-to-end with dual lines in typical shotgun-flow patterns. Both flow patterns are most often in straight line.
Modular wood construction progresses in the following sequence but depends on the manufacturing company in which way they decide to adopt.
Floor construction: the floor is constructed on the factory floor, sheathed and insulated then placed on skids.
Panel walls are the constructed insulated and sheathed and fixed on to the floor.
Roof placement. This could be done on site or in factory where the built roof is craned and fixed on to the walls.
Wrapping of the modules. Here the modules are wrapped with protective gear to ensure airtightness and protection from any weather conditions that may cause any damages.
Placement of windows
Exterior and interior finishes are installed including sidings, gypsum boards and roofing.
Modules are shrink wrapped and loaded onto the trailers
Transported to site
Crane hoisting of modules and setting
Modules are then stitched on-site.
Figure : Modular construction system production schemeBelow is a summary of wood processing technology found in modular home industry in a floor, wall and roof processes.
Handling and transportation
"Quality of housing is a function of performance at every stage of construction and in service. Handling and transportation of building modules is an important part of the overall life of modular houses because for most units that is when they experience the highest mechanical loads" (Smith et al., 2007).
Modular units are designed with adequate resistance to structural stresses and deflection arising from handling and trucking. It is reported that some manufacturers use up to 30 percent more material than would be required with on site, building, construction (Center, 2003).
If the handling causes any damages, these disrupt the continuity in the envelope which affects air leakage and moisture deposition characteristic of the building in service. The induced leakage affects air exchange and heating or cooling characteristics in the short term and durability in the long run.
Structural stresses that develop during the transportation can be caused by the wind and road induced vibrations, braking and centrifugal forces thus weakening the modules and their durability.
From the research carried out on high performance modular wood construction systems, most damages occurred in walls and ceilings of the open living area because that section of the building experiences relatively high forces and has lowest rigidity. Generally it can be expected that portions of modular houses with an open interior and or large wall openings will be susceptible to handling and road transportation damage.
Visible damages were mainly cracks in plasterboard linings of walls or ceilings. The largest deformations, and therefore highest stresses and most initiation of new damages, occurred during lifting operations in the factory yard. This resulted from poor control of the evenness of the ground in the temporary holding area, lack of synchrony in jack movements, and use of insufficient jacking points along the length of the building.
The delays in switching lifting jacks created twisting moments about the longitudinal axis of the modules. Those twisting moments cause cracking in ceilings.
Damages developed during lifting processes can be accentuated during transportation by vibration induced cyclic fatigue processes.
Plasterboard carries more forces than OSB sheathing in proportion to their strengths during lifting processes.
Results shown that significant reductions in stresses and therefore damage can be expected if mini homes are lifted at four jacking points along the long walls, rather than at three points as at present.
Material economies are possible, and especially in terms of reducing the amount and dimensions of lumber framing components, through application of advanced structural analysis of the type reported here. Those models can optimise decisions across the effects of both lifting and road transportation processes.
Foundation Choice
All modules must be placed on a solid and secure foundation and the choice of foundation system depends on the site conditions, design factors and the design practices. A pier and ground anchor support system, crawl space system, slabs-on-grade foundation system, and basement walls could be used as the foundation system but the is a client's choice depending on what his needs are (Alliance, 2002).
The foundations and other site works are constructed simultaneously as the modules are being prefabricated. The site conditions usually dictate the system to be used as each site is different with different conditions.
Figure : Recessed foundation to create a site-built look
Figure : Combination of interior piers and perimeter wallsCHAPTER 5 - DEVELOPMENT OF PRINCIPLES
Introduction
According to the 2009 National Research Council's report on improving productivity in the construction industry, prefabrication or modularisation as the "opportunity for breakthrough achievement" is recommended. The increasing interest in lean construction, the rising use of BIM technologies and the growing influence of green technology have caused many practitioners to reconsider their appeal. The above combined with recent advances in prefabrication makes this a critical trend in the construction industry.
BIM
BIM - Building Information Modelling is a process involving the generation and management of digital representations of physical and functional characteristics of a facility (Committee, 2012).
BIM is increasingly being used to contribute to the potential for increased use of prefabrication and modularisation. In a recent study about the use of BIM on green projects, McGraw Hill construction (MHC) found that the use of BIM model-driven prefabrication on more than one quarter of their projects is expected to increase from 37% to 73% among practitioners who use BIM for green work. Even those who are currently not using BIM expect an increase from 22% to 57%. BIM helps enable prefabrication of tightly integrated MEP systems, allowing designers to maximise space for other uses in high- tech buildings like hospitals (Fitch, 2011).
Lean Construction
Productivity and efficiency in modularisation can be greatly increased if lean production methods are incorporated. In recent years, due to the economic difficulties in the construction industry, there is an appeal of using lean methods and practices.
It can be noted that for
Green Building
Green building has grown into a substantial part of the overall construction market. This has sustained a steady growth throughout the recession. It is predicted that the growth of the market share for green will not abate as the construction industry recovers from the recession. This indicates strong implications for rising interest in prefabrication and modularisation, which helps eliminate waste onsite and conserve resources.
Principles
For a project to run smoothly and productively, the following principles have to be well balanced;
Cost
Cost consists of three aspects for which prefabrication conceptually has solutions: material, labour and time. So if any one of them is reduced, the cost reduces as well. The use of prefabrication does not fully mean a reduction in the project budget but in order to achieve it, there should be a high degree of planning.
In modularisation, materials are procured not only for a single project but perhaps for many projects. The "just-in-time" term, here materials are ever available when needed. This allows the fabricators to manage the production of modules efficiently. As compared to the on-site method, contractors spend a lot of time managing the site and material storage which consumes a lot of their time. The setup of a factory environment for production of goods is a considerable investment.
Labour
In on-site construction, skilled work is required because of the range of tasks involved. A single mistake is detrimental to the progress of the project. It is reported that in most on-site sites, unskilled workers are unsupervised and this is very risky. In most factories, unskilled work is more easily managed and there is supervision during the quality control process.
Prefabrication offers improved working conditions and more stable job market since there is continuous work flow. The temporary availability of on-site work brings about increased stress in the work force. It is viewed that factory workers have a better life style and mental health compared to on-site workers.
Construction workers face a variety of hazards which include physical and mechanical injuries; exposure to noise and vibration, extreme heat or cold, work in windy, rainy, snowy or foggy weather, nonionizing ultraviolet radiation usually from exposure to the sun and electric arc welding, chemical hazards such as dusts, fumes, mists, vapours and gasses as well as psycho-social hazards. Most of these occur when on-site methods are used and greatly reduced when factory fabrication is used. This allows for increased efficiency and productivity in the construction industry.
Time
Reduction in project duration is arguably the greatest benefit to productivity of off-site fabrication. Time is saved as there is simultaneous construction in the factory and site works. If lean production techniques are employed, reduction in schedules can occur through increase in repetition.
As decisions to use prefabricated modules are made earlier before construction starts through integrated process, schedule savings are realized and this gives more predictable dates on when projects are to be finished. This is due to the ability to procure materials and processes more quickly and the production controlled environment where there are no weather interruptions.
Michelle Kaufmann reports that in her experience with prefabrication, comparing two similar houses, the duration was nearly half for the modular prefab than that built on site. The figures below show the duration of the two Glidehouse designed by Michelle Kaufmann and the duration of the projects.
Figure : Comparison of two similar houses, one built on site and the other off-site
Figure : Comparison of on-site versus off-site construction methods by Kullman Building Systems
Scope
Scope of a project refers to the breadth, size complexity and the involvement of individuals and teams required in completing the undertaking. [6] This involves all individuals in the entire design and delivery team as well as the constructors.
Prefabrication allows for integration at both the physical and organisational levels as there is an early involvement of the parties involved in making decisions. This integration of prefabrication delivers a more integrated building system.
This scope of project is controlled when the supply chain management is fully instituted. This means that there should be management of a network of interconnected businesses involved in the ultimate provision of raw materials, end products and services offered. Prefabrication allows for a long supply chain for materials and coordination between the site and plan.
Since design documentations are required at higher detailing levels for assembly, this reduces on the number of errors made during assembly. This gives a predictable output but as well does not allow for easy fix flexibility in case of needs for adjustments and change on site.
Quality
Prefabrication offers a great deal of production quality and less design quality in a way that there are more standardised and unvaried designs. This is a challenge being faced by modularisation and requires more creative abilities of architects, engineers, fabricators and contractors to envision a method to increase both the quality of design and production to the mutual benefit of both.
Risk
It is reported that on projects that use prefabrication to realize leverage on off-site project for its capability to control cost and schedule, all parties assume risk until prefabrication has been tested to outperform on-site methods. Prefabrication enables an integral part of the bidding process to determine costing and bring the design within a constructible and affordable balance. This means that trying to obtain higher quality through more predictable means in the factory offers a lower risk to the undertakers.
CHAPTER 6 - DEVELOPMENT OF MATERIALS
Introduction
Materials are used throughout a building's life, initially and primarily during the construction phase and subsequently for maintenance or for alterations. These materials contribute towards the aesthetics, and appeal of a building to its buildability and cost.
Various materials have been used in the manufacturing of modular units. Precast concrete elements, wood-based boards' products and profiled steel sheeting are increasingly popular because of their high quality and economy of production. [7]
Materials
Steel
In the fabrication of modular units, steel is majorly used for the load bearing structure frame because of its property of high tensile and compressive strength. Steel has a consistent material quality which is an advantage in the structural dimensioning of constructions.
Figure 12: Profile for sheet steel roofing and cladding
Figure 11: Cold rolled Steel sectionsSteel sheet profiles are also being used in modular constructions as corrugated roof and wall claddings.
Timber
Timber or wood is a biodegradable material that is easy to manipulate with hands or mechanical machinery, easy to recycle and reuse. If timber is kept dry, it has a high serviceability.
Solid timber is graded into quality classes; S7, S10, and S13, for the purposes of structural dimensioning. This can be used for all methods of timber construction but usually as columns and beams.
Glued laminated timber is made of at least three layers of boarding in which the fibres are parallel and laminated together under pressure to produce stable building elements. These are stronger than solid timber because only timber without any defects and shrinkage cracks. Gluelam spans greater distances that solid timber members of the same cross sectional size.
Composite wood based beams. These also known as H beams consist of upper and lower chords with a web. They have greater structural depth and have better strength to weight ratio. These are usually used in making building elements subject to bending forces, where the compression and tension forces are carried by the upper and lower chords. These composite wood beams are generally used in walls, slabs, roofs.
Figure : Composite Wooden beams in a floor constructionTimber elements in a factory are usually joined together using engineered elements of steel or cast iron as they are simple and efficient to manufacture and their strengths can be easily calculated. These can as well be joined using steel plates, bolts or screws.
Figure : Application of a gang nailColumns and beams are usually fixed with steel junction plates and the columns connected to foundations by way of plates or angles. They are always mounted on support bases to ensure they are not damaged by water.
Nail plates are usually used to connect timber members to allow longer spans and joins at connections.
Aluminium
Although Aluminium consumes large electricity in its manufacturing, is being greatly used in the manufacturing of modular units' wall panels and external finishing because of its lightness, corrosion resistance and low maintenance properties.
Magnesium Oxide Boards
New materials such as Magnesium Oxide boards which are weather proof boards are being put to use and if the marketing of such materials is developed, they will serve the construction industry well. Magnesium Oxide boards have a higher resistance to fire and mould and mildew control as well as sound control applications. These are environmentally friendly and are being used in replacement of gypsum boards for dry walls and ceiling coverings. These are produced in various sizes and colours and can be used as the final finishing of modules.
Magnesium Oxide (MGO) occurs as a natural deposit but primarily in China where the Chinese government prohibits exportation of the raw material. This then renders it a more expensive alternative to gypsum boards (Anon., 2012). MGO boards are being used together with Polystyrene and steel frames to form wall panels which are light and durable.
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Figure : Magnesium Oxide boards
CHAPTER 7 - CONCLUSIONS AND RECOMMENDATIONS
Many failures in the modular construction have always been because of a lack of integrated process early in the planning stages of a project. Alastair Gibb states that "an overall strategy for offsite fabrication is required because the benefits of prefabrication are not in individual elemental cost, but are realized in possible secondary effects of saved time on site (Smith, 2011)". By working toward selecting prefabrication as the method of implementation early on, it encourages the client, design team, contractor team, and key fabricators to work collaboratively to realize an affordable appropriate technology for a given context.
The goal of modularisation in construction is the reduction of on-site activities used to achieve the lean process and buildability by promoting high productivity. This enables easier management of the lean practices by in-time deliveries, scheduling, quality, and flexibility. But the main question comes in, can lean manufacturing be fully incorporated in the modular fabrication industry and would it improve on flexibility and profitability?
Modular construction is becoming more widely accepted for permanent building uses, this is pushing new boundaries for broader applications of modular units. Modular design and techniques are an excellent solution to meet the needs of people for any construction use offering cost effective and quick building solutions. With energy efficiency and cost reduction being a major focus in recent years, modularisation promises a great deal as compared to the on-site constructions.
Many modular manufacturers offer less marketing and sales services but if these are emphasized on, modular products will gain a place in the building industry thus improving on the way construction offers products.
Joel Turkel of Turkel Design states: "The future of prefab is an increasingly non-architectural problem. Traditionally, architects have tried to design things to be prefabricated using either existing or new means, as opposed to designing functional and integrated delivery methods…Real development for the industry will come from young (professionals) who are able to… think in terms of complete front-to-back business models. They are aware of the needs and limits of manufacturing processes but also are versed in new technologies, entrepreneurial methods, how capital works, strategic partnerships, and the important of marketing and branding. This group will not design buildings but rather solutions for distributed delivery methods…leading the way toward rationalized industry wide changes to benefit us all, rather than just promoting an individual vision or aesthetic (Smith, 2011). "
It is reported that modularisation lowers project costs (85%) and project schedule improvements (84%) are the top drivers behind the current users' decision to use modular buildings or prefabrication in the future (Fitch, 2011). Other top factors driving future use are:
Project quality improvements (70%)
Cheaper labour costs (69%)
Project safety improvement (58%)
In general, once lean methods are fully incorporated in the modularisation industry, the use of integrated project delivery, and a cradle to cradle design implementation, the construction industry will get transformed to an up-to-date sector offering a variety of economic, social and ecological value.
CHAPTER 9 - CASE STUDIES
PEKAPEKA BEACH HOUSE, 2008 New Zealand.
This is a holiday house along Pekapeka beach designed by Gerald Parsonson. It is a simple-seeming long box. It was made of two boxes joined by a transparent mid-section. With a straight-forward design concept, the house is something with four corners, a rectangle in a word. It sits on a light weight raft foundation made of large chunks of polystyrene. The plan is a rectangle and is divided into three sections, the solid bedroom / bathroom forms at each end support a floating roof over the glazed kitchen/ dining / living space in between. The north end holds the main bedroom with its ensuite bathroom; and the south end is the guest quarters.
The layout allows the living room to face both east to the hills and west to the sea. Here the sun is allowed into the house throughout the day, for passive solar heating of the concrete slabs used and creates a sheltered outside space on the east side that still keeps a strong connection to the western sea views.
Figure : Above Left: the living area in the middle section of the house. Above Right: In the void/ dining area, looking to the kitchen with, at left, the entrance to the main bedroom.The house's functions are differentiated on the outside as well, with black fibre-cement sheets, in modular rhythm i.e. the standard sheet-sizes for economy of construction, clad the bedroom ends. The two end boxes read as solid structures for the glazed middle (Anon., 2008).
COPENHAGEN METRO COMPANY, 2007-2008 Denmark.
Type: Office Building, New building.
Area: 4274 m²
Client: Copenhagen Metro Company
Architect: TNT Architects A/S
Location: Ørestad, Metrovej 5, Copenhagen S
Built: 2007-2008
Cost: 60 million. Kr
Energy Class: 2
Figure : Exterior View of the Metro Company officesThis is a new office building owned byhttp://www.scandibyg.com/documents%20and%20images/Gallery/kontorer/kontordomiciler/metroselskabet/original/kontorer_metroselskabet_1530.jpg
Copenhagen Metro Company. It is made of 2 stories high and consists of 2 wings connected by a large entrance area with a reception and a canteen with access to an outside court yard terrace.
The entrance area has a skylight, a fully visible walking bridge connecting the 2 wings and the walls are fitted with acoustic strips.
Figure 15: Interior view of the Metro Company OfficesThe interior is kept in light colours with grey linoleum and ash wood floors.http://www.scandibyg.com/documents%20and%20images/Gallery/kontorer/kontordomiciler/metroselskabet/original/kontorer_metroselskabet_1545.jpg
The building is composed of smaller closed offices, open offices, and conference rooms.
And the exterior is covered by grey coloured eternity. The entire building was built using 116 modules or boxes which transported to the building site from the Scandibyg factories located in Løgstør (Anon., n.d.).
