Al i s ta i r G.F. Gibb

prefabr icat ion pre-assem bly

Partone CONTEXT

This part defines and codifies off-site fabrication in order to enable further evaluation of principles and applications.

1.1 Scope of off-site fabrication

I 1.1.1 What is off-site fabrication?

Off-site fabrication in its broadest sense encompasses many contemporary construc- tion techniques, with perhaps the simplest prefabricated component in use throughout most of the world being the building brick or block. At the other end of the spectrum, whole buildings are prefabricated and pre-assembled remote from their final destina- tion and installed in place with only the minimum of on-site work needed before they are fit for use.

Many have previously sought to define off-site fabrication, or to use other words to describe the basic principles behind the approach. For example in a foundational report for the Construction Industry Institute (CII) in the USA, Tatum et al. (1986)

‘Prefabrication is a manufacturingprocess, generally taking place at a specialised facility, in which various materials are joined to form a component part of the final instullation. ’

‘Pre-assembly is a process by which various materials, prefabricated components, andlor equ@ment are joined together at a remote location for subsequent installa- tion as a sub-unit. It is generally focused on a system.’

The Construction Industry Research and Information Association (CIRIA, 1997) defines pre-assembly as follows:

‘Pre-assembly: For a given piece of work, the organisation and completion of a substantial proportion of its final assembly work before installation in its final position. It includesinany forms of sub-assembly It can takeplace on or o f f i t e , and often involves standardisation.’

In this book, the term off-site fabrication is used to cover both prefabrication and pre- assembly as described in the CII and CIRIA reports and can be defined as follows:

I define prefabrication and pre-assembly as follows.

I

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OFF-SITE FABRICATION

‘Off-site fabrication is a process which incorporates prefabrication and pre- assembb. The process involves the design and manufacture of units or modules, usually remote from the work site, and their instullation to form the permanent works at the work site. In its fullest sense, off-site fabrication requires a project strategy that will change the orientation of the project process from construction to manufacture and installation.’

The units produced by off-site fabrication are variously described using terms such as ‘pods’, ‘units’, ‘modules’ or ‘assemblies’. Tatum et ul. (1 986) define a ‘module’ as a ‘major section of plant (Tatum was working within the petrochemical and process plant sector where much of the prefabrication involved items of plant) resulting from a series of remote assembly operations and may include portions of many systems. It is usually the largest transportable unit or component of a facility’

The term module may however be misleading in that it has a different, well under- stood meaning: ‘a standard unit of length which is repeated many times and controls the sizes of components and the layout of a building’(MacLean & Scott, 1993). Fur- thermore, pre-assembled modules are considered, by some, to be essentially modular in nature. In other words, they must be joined together in an pre-ordained sequence or arrangement to form a larger building or facility. Whilst this may be the case for modular structures such as offshore oil platforms (where much of the late twentieth century volumetric modular thinking developed), in most cases the units are not joined in this way. Furthermore many are far from modular in that they are of different shapes and sizes and may be made as ‘one-offs’ for a particular project. In this book the term ‘module’ is avoided wherever possible, with the more general term ‘unit’ used instead.

1.1.2 Off-site fabrication and standardisation

CIRIA defines standardisation as ‘the extensive use of components, methods or proc- esses in which there is regularity, repetition and a background of successful practice’ (CIRIA, 1997). MacLean’s Dictionary of Building (1993) defines industrialised build- ing methods as ‘involving a high degree of prefabrication, often of the structural fram- ing, roof, and cladding, so as to reduce site work to the minimum. This involves careful planning, and the maximum standardisation. The quantity of factory work on the building elements is deliberately increased so as to reduce the cost and improve the quality and speed of construction.’

Standardisation and off-site fabrication are considered by some as synonymous CIRIA found that whilst they can be used individually the greatest benefit is when they are used together (CIRIA, 1997). Others argue that benefits from advances in manufacturing industries can only be realised in construction where standardisation is accepted. However, this belies the true advances in manufacturing where mass customisation has taken over from mass production, which was developed by Henry Ford and others for automobile manufacture in the first half of the twentieth century. With high-powered computer-aided design and digitally controlled manufacturing machinery there is no longer the necessity for ‘identical’ standardisation. Mass

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CONTEXT

customisation requires flexible production lines to produce a range of alternative assem- blies to produce a variety of end-products which meet individual customer require- ments. More effort is placed on the standardisation of interfaces between components which allows interchangeability and maximises choice.

There is therefore the full spectrum of bespoke to standardised products available for off-site fabrication. Project teams must identify where benefit can be gained from choosing‘made for stock’ rather than ‘made to order’items. The situation will depend upon the manufacturer’s organisation and facilities. As an example, Figure 1.1 shows the cost benefits for standardisation of precast cladding units. In this case, based on timber moulds, the minimum repetition for cost-effective manufacture is around ten units with an optimum repetition of 30 units. After this the added benefit gained from more repetition becomes less significant, however with less standardisation the project will incur a cost premium. A similar graph could be drawn for other off-site fabricated items, but in each case the minimum cost-effective number will be different. Clearly project teams will benefit from early involvement of the manufacturers to ensure that appropriate standardisation to suit each unit or component is adopted.

I

700

500

300

100 30 20 10 1

Unit repetition

Figure 1.1 for precast concrete cladding. Courtesy of Trent Concrete

Relationship between unit cost and unit repetition (stundurdisation)

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1.2 Codification of off-site fabrication

1.2.1 Extent of off-site fabrication

Most building projects can be subdivided into a number of primary elements, namely: Foundations and works below ground. The structure of the building. The external walls and roof that form the perimeter of

the building. The mechanical and electrical building services

distribution. The internal walls, raised floors, suspended ceilings and

applied finishes such as plaster, paint, wall coverings, etc.

The major parts of the building that are generally provided by the developer for the use of the end-user, such as the toilet/washrooms, kitchens, lifts/elevators, plant rooms, building management system rooms, etc.

Substructure Frame Envelope

Services

Internal works

Facilities

Most civil engineering projects can be subdivided into the following primary elements: Foundations and works below ground. The structure itself For civil engineering projects this is

usually the most significant element. The mechanical and electrical services where applicable. Additional specialist items that are necessary for the

Substructure Structure

Services Special equipment

function of the project.

Most process plant (or power generation) projects can be subdivided into the follow- ing primary elements:

Substructure Frame and envelope

Foundations and works below ground. The structure of the facility and the external walls and

roof that house the process plant. These two items are often considered together.

user’s business. For example, process plant, manufac- turing machinery, along with all necessary supply and waste removal services and distribution. For process plant projects this is almost always the major element, and all other aspects are subservient.

The extent of off-site fabrication for projects can be established by considering which of the above elements are included, and how much work on each element is left to be completed at the worksite.

Model examples for a commercial building, a civil engineering project and a proc- ess plant facility are given in this section (Examples 1.1, 1.2, 1.3). Such examples are

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Process equipment The plant and machinery which form part of the end-

CONTEXT

indicators of the possible extent of off-site fabrication. However, they must not be interpreted legalistically, as the optimisation of off-site fabrication requires detailed consideration of factors such as the client’s business needs, site opportunities, prevail- ing manufacturingkonstruction culture, and so forth.

Example 1.1 Commercial building model

This model example demonstrates the possible extent of off-site fabhcation for a major multi-storey commercial building. Detailed applications will need to be determined for each project.

Substructure Foundations Both piled and pad foundations are available as precast concrete elements. Basements Precast concrete wall elements may be included. Typically, basement floors tend to be concreted in situ. However, for multi-basements, especially using top-down construc- tion methods (where the lower slabs are completed after the ground level slab), struc- tural steel or prestressed precast concrete is usually used. The extent of off-site fabrica- tion will often be limited here by the restriction in access to the work face. Items of mechanical and electrical plant in basements are often prefabricated. Drainage and underground services Other than the use of large section (or even continuous) pipe lengths, off-site fabrica- tion is not often used.

Frame Structural steel Structural steel frames, by their nature, incorporate off-site fabrication. In many cases larger sections comprising several individual pieces are pre-assembled, either off-site or at ground level, adjacent to their final position. Extent of pre-assembly will depend u p p transportation and craneage opportunities and restrictions. Many steel-framed buildings will use prestressed precast concrete floor units. Reinforced concrete Precast concrete frames (with, or without prestressing) are naturally prefabricated off- site. Size and shape of units will depend upon transportation and craneage opportu- nities and limitations. In situ concrete frames may use pre-assembled formwork or falsework to support the concrete during casting. Steel reinforcement cages may be pre-assembled (usually on-site) and then placed within the concrete formwork. Structural timber Timber-framed buildings are common in many countries, even for multi-storey struc- tures. In the UK timber-framed buildings using off-site fabricated units have been used for buildings up to five storeys with recent research indicating seven stories may be viable. Nevertheless their use is mainly as residential rather than as commercial buildings.

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Services Distribution network The distribution network for mechanical and electrical services can be pre-assembled off-site. This can include vertical riser sections complete with framing, access platforms and insulation and also multi-service, plug-in modules for horizontal distribution. Sizes and details will depend on the project parameters and access limitations Plant rooms Off-site fabricated plant rooms have been used effectively on many projects, especially where they can be located on the roof of the building.

Internal works Ceilings and floors Most commercial buildings incorporate off-site fabricated systems for suspended ceil- ings and raised access floors. The component sizes are usually fairly small but still facilitate very rapid site installation. firtitions ‘Permanent’ partitions may be constructed using traditional concrete blockwork, or more frequently a metal frame and gypsum board walling system. Various off-site fabricated partition systems, usually with posts and panels, are used where relocatability is desirable.

Facilities Washrooms and lifis Most of the facilities provided by commercial developers can be assembled off-site. Ofice washrooms and elevator/lift shafts are typical. These are usually areas of high value and complex construction and therefore can gain greatest benefit from off-site fabrication.

Complete modular building Generally, a complete modular building approach is better suited to smaller medium- rise developments However, various manufacturers are developing systems that can be applied to larger, and taller, buildings

Example 1.2 Civil engineering model

There is a greater spectrum of civil engineering projects than building project types, therefore it is even more important that the application of off-site fabrication is consid- ered for each project and decisions made based on the specific project characteristics.

Substructure Foundations and substructure for civil engineering works are usually bespoke designed and constructed in situ. However, project-designed precast concrete units can be used to good effect.

Structure Many civil engineering projects use precast concrete, or pre-assembled structural steel

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CONTEXT

units for their structure. In many cases irz situ construction may not be feasible (e.g. many bridge projects)

Services On many civil engineering projects services such as electrical substations or generators can be successfully pre-assembled off-site. These off-site fabricated units may also include the buildings that surround them.

Special equipment Clearly special equipment such as handrails, signage and client machinery can be, and often is, assembled off-site either as complete units or as sub-assemblies.

Example 1.3 Process plant model

Substructure Precast concrete foundation units may be applicable dependent upon the project par- ameters.

Frame and envelope For many process plant or heavy engineering projects the building is seen solely as a provider of a suitable environment for the process equipment. Structural steel frames and metal cladding are typical, both of which can utilise off-site fabrication. The building usually represents a small percentage of the overall project cost and therefore greater cost benefits can usually be gained by considering off-site fabrication for the process equipment itself.

Process equipment In many cases in recent years process equipment has been ‘modularised’ into large volumetric units pre-assembled off-site. Reasons for this off-site fabrication of proc- ess equipment include a shortage of local labour capable of doing this work on-site, and the sensitivity of the plant requiring clean factory conditions for assembly. Most process plant developers are themselves part of the manufacturing sector and there- fore can bring this expertise to the building process.

1.2.2 Types of off-site fabrication

In 1965, White defined prefabrication as ‘a useful but imprecise word to signify a trend in building technology.’ He argued that if prefabrication was related to every factory manufactured product, the term ‘could be stretched so wide as to lose all meaning’ (White, 1965). In support of White’s view, this more generic and small-scale ‘off-site fabrication’ has not been covered in this book, rather, the types of off-site fabrication have been established as non-volumetric off-site fabrication, volumetric off-site fabri- cation and modular building.

These types are described in more detail in the following sections, and examples are gven in Part Three. However, it should be remembered that the dividing line between each type is not immovable, and many applications will involve more than one type.

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1.2.3 Non-volumetric off-site fabrication

The term non-volumetric may be somewhat misleading since all the units and systems produced will have some volume. However, it is used to mean items that do not enclose usable space, to distinguish it from volumetric off-site fabrication.

Non-volumetric off-site fabrication includes solutions that are generally made up of one of the elements listed earlier (Section 1.2.1). Typical examples would be parts of the structural frame or cladding of a building, internal partitions, parts of building services, distribution ductwork or pipework and so forth.

1.2.4 Volumetric off-site fabrication

The volumetric off-site fabrication category comprises units that enclose usable space, but do not of themselves constitute the whole building. Most units are substantially complete in themselves, leaving only a small amount of work to be completed on-site.

Volumetric off-site fabrication is mainly used for ‘facilities’ as defined in Section 1.2.1, and includes solutions such as ofice toilet/washrooms, plant rooms, building services risers, and lifts. These units are generally installed within a new or existing building structure, and do not usually provide any support for that structure.

1.2.5 Modular building

This category comprises units that form a complete building or part of a building, including the structure and envelope. Most units are again substantially complete in themselves, leaving only a small amount of work to be completed on-site. However, some systems, especially for multi-storey construction, provide only the structure and sometimes cladding, and are then finished on-site. The term ‘modular building struc- ture’ is used in this book to describe such systems. For units that are fully finished off- site this category provides a complete off-site fabricated building - a ‘one-stop’ sys- tem for a client wanting a cost-effective and relatively straightforward building.

Examples of modular buildings include medium-rise ofice or hotel accommoda- tion, stand-alone retail units, housing (in some countries), and a wide variety of temp- orary or relocatable solutions.

1.3 Historical context The construction industry’s transformation from ad hoc building to planned multiple production has been achieved by a series of marked developments of which off-site fabrication is probably the most pronounced. Off-site fabrication is not that new in itself Specialist books dealing with timber buildings date off-site fabrication to the twelfth century (Hewett, 1980). Industrialised building techniques however have not developed steadily and consistently but rather have evolved in a sporadic fashion, even being totally disregarded at times.

Since the beginning of the 1980s commercial clients have become more pragmatic

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CONTEXT

in what they expect the construction industry to deliver. They have demanded a better quality product, delivered faster and at reasonable cost. Broberg (1986) states that ‘The twentieth century has seen the breakthrough of industrial methods and thinking in most areas of production. In building, however, industrial concepts have only been partially accepted.’ Great Britain’s construction industry has seldom consciously aimed at industrial methods for its own sake.

Off-site fabrication has developed in response to a number of external factors such as:

Sporadic urgent demand for buildings or facilities e.g. British colonialisation and the subsequent need for rapid European-style housing

Changes in business practice causing rapid commercial development in London in the late 1980s

Rapid response to natural disasters such as earthquakes The industrial revolution in the developed world changing both the manufactur-

Changing fashion where a prefabricated appearance is alternately either desirable

Advances in technology in other sectors combined with a desire for technology

Increase in labour costs driving the desire to optimise labour utilisation and pro-

Decrease of available skilled labour at the worksite driving the need for a stable

Changing client expectation e.g. a desire for more predictability in project out-

Development of digitally controlled manufacturing facilities and high-powered

Increased concern for health and safety of workers driving the desire to reduce

ing capabilities and public perception of the desirability of industrialised products

or to be avoided

transfer

ductivity

skilled workforce at the manufacturing facility

comes

computer-aided design systems giving more flexibility to manufacturers

more hazardous on-site work

Figure 1.2 shows how the influence of these factors has affected off-site fabrication over time. Whilst the graphs are only indicative it is clear that there has been a general increase in the influence of such external factors over the last 150 years.

A full historical analysis of off-site fabrication is outside the scope of this book. Therefore, the development of industrialised building techniques in the medical care sector is provided here as a case study from Roman army hospitals in the first century AD to contemporary practice at the turn of the twenty-first century.

Case Study 1.1 Historical development of off-site fabrication in medical care buildings

The Roman era The construction of highly prefabricated structures in the British Isles by the Roman army was established by the work of the late Professor Sir Ian Richmond. The largest

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OFF-SITE FABRICATION

1850 1875 1900 1925 1950 1975 2000 British Colonial Developments wwI WWll

Various natural and 'man-made' disasters Sporadic Urgent Demand

World-wide elfect

Industrial Revolution Continuing level of industrialisation

'Svstem

No real effect Changing Fashion

Ford mass production Industrialisation

Japan mass Other Sector Advances customisation

Late 20th Century

No real change Increased Labour Costs

Decrease in Skilled Labour ~~~~~

No real change Changing Client Expectation

Non-existant IT and Digital Controls

Becoming

Little understanding 01 H8S Concern for Health 8 Safety

1850 1875 1900 1925 1950 1975 2000

Figure 1.2 The historical influence of external factors on offsite fabrication.

of these was the Legionary Fortress at Inchtuthil, Scotland. Its archaeological excava- tions, under the direction of Sir Ian and his assistant Professor J. K. S. St Joseph, are detailed and illustrated in Pitts & St Joseph (1985). Constructed under the governor- ship of Gnaeus Julius Agricola between AD 83 and 86, Inchtuthil's 170 buildings include a large 600-bed hospital.

The industrialised war Inadequate hospital provision during the Crimean War resulted in a 42% death rate within the troops which was highlighted in 1854 by Florence Nightingale (Taylor, 1991). Initially, to relieve this suffering, prefabricated timber houses and huts were converted into makeshift hospitals (Herbert, 1978). Dr Smith, director of the medical

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CONTEXT

department of the army, wrote to Dr Hall, the Inspector General of Hospitals, and was highly critical about ‘the adequacy of the huts, as some were not watertight’ (Herbert, 1978).

Galvanised by public outcry, the War Ofice commissioned lsambard Kingdom Brunel to design a field hospital. Brunel not only designed the hospitals but invented a system of complete Fabrication. He wrote: ‘The construction of each building has been studied with great care, so as to secure the minimum amount of material, the least possible amount of work in construction or erection, and the means of arranging all the parts in separate packages, capable each of being carried by two men’ ( Herbert, 1978).

For the hospital at Renkioi, Turkey, the units came complete with plumbed bath- rooms, washrooms and toilets, a storeroom, an operating room and a nurse’s room. Rooms came equipped with long narrow windows, fitted under the eaves, to protect them from the sun’s direct rays and providing good natural ventilation. This was supplemented by a room for mechanical ventilation which pumped humidified air through ducts throughout the length of the pavilions to combat the natural dryness of the air. These individual units were combined to provide 100 foot long, 40 foot wide by 25 foot high pavilions (Thompson et ul., 1975).

Portable field hospitals were developed by Britain’s Crimean allies, by the French and by other European armies. Bender (1993) explains that similar flatpack hospitals were used extensively by both sides during the American Civil War. They were based on the principles developed in Florence Nightingale paper Notes on Hospituls, pub- lished in 1858. The largest of these hospitals was the Confederate Army’s I50 white- washed wooden barracks, Chimborazo Hospital, accommodating 7,000 patients.

Notwithstanding these developments, within fifty years, during the Boer War, British soldiers were dying in unprecedented numbers through inadequate shelter for medical care. This was despite the fact that South Africa was an important export market for British off-site fabrication companies in the civilian sector (Herbert, 1978).

Industrialised building methods The mid-nineteenth century was the beginning of the industrialised age and prefabri- cated cast-iron had made a dramatic impact at the Great Exhibition of 185 1, with the Crystal Palace. However, Brunel’s portable hospitals were constructed using timber, with the wall panels faced in galvanised sheeting. By the late 1850s companies were manufacturing corrugated iron buildings for use at home and abroad. One of the largest manufacturers was Charles D. Young & Co. of Edinburgh. They undertook large contracts at both Aldershot and Colchester for the provision of iron barracks which included hospital accommodation based upon government proposals (Herbert, 1978). Herbert describes an ambitious 200-patient hospital proposed by Young: ‘This was a two-storey building with a modular structure of cast-iron and corrugated iron infill panels. I t is not known, however, if this design was ever actually executed.’

1880s to 1945 A series of smallpox and scarlet fever epidemics spread across the UK during the last quarter of the nineteenth century. London’s smallpox epidemic of 1880 resulted in the

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forced introduction of temporary camps supplemented with hospital ships (Taylor, 1991). The concept of hospitals as temporary structures, allowing a rapid response at the onset of an epidemic, was a recurrent theme during this period. The hospitals were made from prefabricated elements which could be quickly erected and then quickly dismantled. Disinfection was by destruction and removal.

The proliferation of these prefabricated structures was not without its critics. Taylor (1991) cites the architect William Henman in a 1900 lecture entitled ‘Modern Hospi- tal’. Henman expressed a practitioner’s warning that ‘temporary buildings if frequently destroyed and replaced by new ones, are far too expensive; the best of them will not compare in comfort and convenience with those that are of more permanent construc- tion, and, as a matter of fact, the so-called temporary buildings are too often permit- ted to exist and be used long after they ought to have been destroyed.’

Designs for these hospital units were prepared by the Metropolitan Asylums Board, from the comprehensive standardised product range of the manufacturers and suppli- ers of prefabricated iron structures Herbert (1978) explains the diverse range of build- ings available in prefabricated form plus the various components available from which to customise a building.

The limited use of prefabricated hospitals in the UK was in marked contrast to events elsewhere. An unidentified source giving evidence in 1903 to the Royal Com- mission on the war in South Africa, states that ‘the German army, in time of peace, provided huts based on well known, well studied systems, capable of being packed into boxes and carried, and put up anywhere. England had not one of these, and there was the very greatest want of them’ (Herbert, 1978).

The beginning of the twentieth century saw the development of TB sanatoria to counter the growth of tuberculosis. These permanent sanatoria comprised a series of 100-bed blocks at a cost of E350 to E650 per bed (Taylor, 1991). In 1907, the architect E. T. Hall (who had built the TB sanatorium for the Brompton Hospital at Frimley, Surrey) presented his proposals to the Architectural Association for a standardised, expandable and prefabricated basic sanatorium design. The design had been devel- oped to respond to a challenge that Hall himself had posed at the Royal Sanitary Institute in 1905 -‘How to erect cheap sanatoria for the millions? The design com- prised a simple, one-storey, linear arrangement of single- or twin-bedded wards com- plete with floors and smooth internal wall surfaces ready for painting, and could be delivered to sites for immediate erection. The concept design seems to have fallen foul of the local government by-law’s requirement for 9 inch (225 mm) thick walls. Taylor (1991) comments that Hall also raised the longer-term questions relating to the rela- tive benefits of temporary, permanent or cheap prefabricated sanatoria to meet the pressures of the early 1900s by asking ‘to what use the permanent buildings for con- sumption could be put when consumption was eradicated?’

The need for hurriedly erected prefabricated accommodation arose again at the onset of the Second World War. Prefabricated Nissen huts were brought into service as makeshift wards, whilst at some hospitals, such as Barnet Hospital in north Lon- don, prefabricated concrete huts were installed. In 1995, eight of these late 1930s structures were still being used for convalescing heart patients (Barrick, 1995).

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CONTEXT

1945-1990

The backbone of Britain’s new National Health Service (”S) was to be 600-900 bed district general hospitals, which were soon upgraded to accommodate 1200-1 800 beds (James, 1986). By 1975, prompted by savage cuts in public expenditure, Dr David Owen, the Minister of Health, announced a totally new method for hospital planning: the creation of small 300-bed ‘nucleus’ hospitals (anon, 1975). These were to be of standardised design, generally two storeys high with a maximum of three storeys. Weeks (198 I ) explains that ‘the nucleus hospital planning system has a respectable ancestry. This includes Brunel’s Renkioi Hospital in 1855, the Vale of Leven Hospital near Glasgow in 1955, (a cluster of identical prefabricated two-storey buildings, each one containing a hospital department and attached to a rather grand three-level street system), and the ill-fated Harness system, also developed by the UKs Department of Health and Social Security (DHSS).’

There is little evidence that the industrialised building techniques that proliferated in the UKs post-war house-building programme were adopted by the hospital sector. During the 1960s and the early 1970% hospital contractors generally used traditional construction methods Off-site fabrication techniques, where used, were generally lim- ited to precast concrete components, for example, an in situ concrete structural frame clad with external precast concrete panels. These panels could be smooth or textured ‘shutter-faced’ as at the University Hospital of Wales, Cardiff, which also incorpo- rated precast concrete mullions to the ward windows.

UK hospital buildings during the mid to late 1970s were normally constructed with an in situ concrete structural framework clad in a variety of basic materials Metal and glass curtain walling became a favoured form of external glazing. These tech- niques are illustrated at Charing Cross Hospital and St Thomas Hospital Phase 11, both in London.

By the mid 1970s private healthcare companies entered the market-place. Refer- ring to Wellington Hospital, Weeks (1977) states that ‘it is possible to see a new stand- ard-setter for private hospitals It would be simplistic to say that it seems more like a hotel than a hospital.’ Whilst the construction principles were identical to the Govern- ment’s NHS hospitals, the quality of the external materials was more luxurious Wel- lington Hospital is faced in Travertine marble, whilst the cladding materials of Charing Cross and St Thomas’ Hospitals are glazed ceramic tiles 1990-2000 and beyond Throughout the 1990s healthcare provision in Britain has seen its most radical trans- formation since the introduction of the NHS in 1948. This is reflected in its new organisational structure, the range and delivery of the medical treatments available, the financial mechanism for providing new premises and the remodelling of its exist- ing estates; all of which are required to deliver a modem cost-effective health service.

Prior to 1990 all hospital developments were led by the fourteen Regional Health Authorities The 1990 National Health Service and Community Care Act has set up a kaleidoscope of health authorities, autonomous trusts and fund-holding general prac- tices. Other radical changes included, in 199 I , the loss of Crown Immunity which had exempted the health sector from statutory building and planning controls.

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The late 1990s has seen the growth of the Private Finance Initiative (PFI) in the UK where much of the funding for projects is raised from the private sector, and developers not only build the facilities but operate them after completion. In his 1994 budget, the then Chancellor Kenneth Clarke announced that all healthcare projects had to seek private finance alternatives. This has led to renewed interest in cost-effec- tive design and construction which includes optimisation of off-site fabrication. Larger hospitals have adopted similar approaches to the commercial development sector and applied off-site fabrication to areas such as structural frames, cladding, plant rooms, and even complete operating theatres. Modular buildings have also been used to pro- vide complete medical facilities. Many of the smaller health trust clients have little in- house project management expertise and may therefore be well suited to the modular building’s ‘one-stop service’ approach to providing buildings.

However, the utilisation of off-site fabrication, and in particular volumetric and modular building techniques, is still limited in the healthcare sector. Research at Lough- borough University investigated 74 post-I 990 UK healthcare construction projects to identify building techniques. The volumetric off-site fabricated unit approach was used on only three projects, with two projects using modular building techniques

Acknowledgements

This case study uvas researched by David Phillips, MSc, Loughborough University.

1.4 International context

1.4.1 Globalisation

Some aspects of off-site fabrication transcend national boundaries. The factory envi- ronment will always offer better opportunities to improve quality, productivity, and health and safety. Furthermore the globalisation of society in general has conspired to remove many national distinctions and encouraged world-wide acceptance of cer- tain key consumer goods, fashions and processes. Many major construction clients, contractors and designers operate throughout the world, thus exporting many of their preferences, techniques and approaches. This globalisation is not an entirely new phe- nomenon. For example, during the British colonial expansion of the nineteenth cen- tury prefabricated buildings were exported from Britain to Central and Eastern Eu- rope, the Middle East, Northern and Southern Africa, Asia, the Far East, Australia, and North and South America.

This globalisation is prevalent in certain construction sectors such as civil engi- neering or petrochemical and process plant projects, and also in major urban develop- ments where the ‘international’ style of architecture has become the norm. However, some issues affecting off-site fabrication vary depending on the national context. Sarja (1998) has produced an international review of off-site fabrication in a report for the Conseil Internationale de Batiment.

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CONTEXT

1.4.2 National distinctives Developing vs developed countries: use of labour Many developed countries have a prime desire to reduce the labour input for any product or commodity. This is because, in most cases, labour forms the main part of the overall cost. However, in many developing countries this is not yet the case. Further-

, more, some countries seek employment of as much labour as possible as a legitimate goal for their national and individual development. Off-site fabrication in itself does not reduce the amount of labour, instead it changes the location of the work and the associated workforce. However, many suppliers understandably choose to automate, or otherwise industrialise, the processes involved and thereby reduce the labour re- quirement. Furthermore, off-site fabrication need not necessarily reduce the use of skilled labour. Again, this is affected by the processes chosen, and the extent of indus- trialisation of the manufacture. The main point here is that off-site fabrication can be used as part of a strategy to reduce labour where this is desired, or to use the available labour more effectively, where labour employment is a benefit.

Cultural differences affect form and style Many developed countries have used off-site fabrication in various forms for many years, and each has developed systems that suit its own architectural and cultural heritage. It is not wise to assume that a system or approach that works well in one country will automatically succeed in another. For example, high-rise living accom- modation in the UK failed in the first instance for social rather than technical reasons The event that caused its final demise was the Ronan Point disaster, where the whole corner of a multi-storey block in London’s Tower Hamlets collapsed following a gas explosion. This accident, and other events, exposed the structural and workmanship deficiencies in the systems, but although these were addressed, high-rise dwellings were not to be repeated in the UK. However, in many other countries (such as Singapore) this approach continues to be the solution to urban housing shortages

To extend this issue further it is useful to cite South Africa. One of the main priorities of the multi-ethnic democratic government that followed the apartheid era was housing for the people. As explained above, the approach in many countries has been to produce system-built high-density, high-rise developments But in South Africa, the concept of personal space and being in direct contact with the land is paramount. Most people want their own plot of land with their own dwelling. As a result, the high-density approach that is often associated with off-site fabrication is inappropri- ate. The challenge for South Africa is to find a solution that can benefit from the system approach and yet meet the needs of the people.

A full international review of off-site fabrication is outside the scope of this book. However, the following cases (Case Studies 1.2-1.5) illustrate particular approaches as a resource for potential developers Because of the one-off nature of many larger building or civil engineering projects, much of the international comparison concen- trates on housing developments, so the residential sector has been chosen for these cases Whilst the housing sector has certain distinctive characteristics, many applica- tions can be transferred to other sectors

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OFF-SITE FABRICATION

Case Study 1.2 Japan: an example of industrialised housing construction

In 1996 a UK Department of Trade and Industry Expert Mission reported on their observations of Japanese prefabricated house-building industries (Groiik et al., 1996). They identified several critical aspects evident in the Japanese approach:

The market structure and attention given to providing customer choice in bespoke housing on individual sites.

The nature of housing as a product. The dominance of new-build and absence of a developed market in second-hand

houses. A distinct framework for innovation formed by government and industry, includ-

ing regulations, and public and private investment in research and development focus- ing on production methods and customer requirements.

The concept of industrialisation as a means to customer choice, to maintenance of built quality, and to flexibility of site operations, rather than simply a means to reduce unit costs.

A strong commitment to developing electronic data models of building processes and buildings as products in use, which could lead to the integration of digital data and its access by a wide range of participants.

They concluded that many of the assumptions which dominate the UK approach to housing are interpreted differently in the Japanese context. They provide ideas and approaches from which UK industry may be able to learn; they also suggest areas in which the UK may be able to offer lessons for Japan.

Over recent years, there have been similar visits to Japan from many western countries. Following one such visit, US housing consultant T. E. Nutt-Powell(l985) identified one of the main lessons from the Japanese approach as vertical integration of the supply chain. ‘The same company handles production, on-site installation, finishing of the interior and exterior, marketing, financing, and even care of the home after its owners have moved in. This enables the firm to develop name recognition of its product, making marketing easier, and releases more capital for developing new products.’

Whilst praising the Japanese approach, Nutt-Powell warns against blindly apply- ing their techniques and approach to other countries. He points out various unique aspects of the Japanese situation. ‘A large proportion of Japan’s population lives within a 450 km corridor linking Osaka, Kyoto and Tokyo whch means that the target area for housing is fairly contained.’ Japanese houses are usually small and keyed to dimensions that are multiples of the traditional “tatami” floor mat. Japanese house manufacturers primarily serve the luxury market. There are relatively few producers: the top five firms make 75% of the country’s manufactured housing. The same manu- facturers, or their subcontractors, also manufacture many of the functional compo- nents of houses such as ‘unitised’ bathrooms (i.e. volumetric prefabricated units). Seis- mic considerations are of great importance in Japan, and influence their designs.’

A willingness to exchange ideas to help develop the sector as a whole.

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CONTEXT

Nutt-Powell was also surprised that much of the work on Japanese manufactured housing is still done on-site. For example, almost all of the interior and exterior finish- ing, and (except in the case of unitised bathrooms and kitchens) plumbing and electri- cal work are all completed on-site after unit installation.

Case Study 1.3 Rationalised house building methods and materials used in the Netherlands

Building methods which make far greater use of factory-finished components such as roofs and walls have been commonplace in Holland for the past 30 years, and are not confined to the social housing sector. Furthermore, they do not have the negative connotations that system building has in the UK. Typically a Dutch housing scheme will utilise a hybrid method of concrete shell or traditional construction, or variations thereof. It is not system build. With the exception of timber-framed housing, all the houses have concrete floors and use the roof space as habitable andor storage space. The method and materials used may be partly determined by the number of houses involved, the client’s requirements and the budget. This case study describes a typical housing development in the Netherlands The main applications of off-site fabrica- tion are roofs and wall panels.

Description of materials and method of construction For schemes in excess of 50 dwellings, rationalised fast-track housing techniques would be employed. The method utilises steel tunnel formwork to cast in situ cross walls, gable walls and floors in a single operation in an inverted U shape, including the incor- poration of electrical and plumbing conduit and ducting to toilet, bathroom and kitchen areas. The use of concrete gives advantages in terms of noise insulation. The finish on the concrete wall surfaces enables painting or wallpapering without the need for plas- tering. Where schemes are less than 50 units and where tunnel formwork would not be justified economically, the Dutch would nevertheless use a concrete slab construction of one sort or another. This type of construction affords the necessary strength and stability for a roof space that can be utilised, and eliminates load-bearing walls, giving greater design flexibility. The slab can be in conjunction with brick and block walls, or concrete walls.

Front and rear elevations are of prefabricated, insulated, timber cavity inner leaves, incorporating windows and doors and subsequently faced in brickwork. Roofs are prefabricated, hinged timber roof elements, incorporating a roof-light and vents. The buildings are therefore weather-tight from the time the wall cladding and roof ele- ments are installed and internal work can proceed in parallel with the brickwork and roof tiling.

Figure 1.3 shows the tunnel-form concrete structure with the prefabricated front wall units installed. The next operation is roof installation. The upper concrete walls to the right-hand units are still being concreted, which demonstrates the speed of installation of the prefabricated wall units Figure 1.4 shows the front elevation of a unit with the wall panels in place and the access gantry ready for roof installation. Internal work on the partitions has already begun.

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OFF-SITE FABRICATION

\

L Figure 1.3 installed.

Tunnel-form concrete structure with prefabricated front wull panels

- ? f --

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Figure 1.4 Front elevution showing wall panels and temporary access guntry for installation.

roof

CONTEXT

Internal partitions are entirely non-load-bearing using a smooth-faced gypsum block requiring no plastering. Ceilings and walls above tiled areas have a sprayed plaster finish. Remaining walls are tiled, papered or painted direct onto gypsum block walling. Prefabricated timber staircases are used. Door sets comprise pre-finished steel door frames incorporating architraves and pre-finished timber doors. Roof The prefabricated timber hinged roof elements are designed to sit on wall plates at the eaves and on the party or gable walls The roof will most likely consist of two elements and a completion time of one hour per house is normal for a team of four operatives and a crane. The elements come to site ready for tiling, complete with roof-light and vent outlets as necessary and are hoisted into place by crane. After frame installation the conventional concrete interlocking tiles are installed. If desired, the sofit sheeting can be a laminated material requiring no decoration. A dry ridge detail is incorpo- rated. At the eaves of the attic a knee partition is usually constructed to allow for additional load distribution. This partition is finished with sliding panels providing eaves storage space. The weight of the roof is approximately 20 kg/m2. Figure 1.5 shows hinged roof elements. The top panel has a preformed cut-out for a roof light and the black primer at the guttering edge. Figure 1.6 shows the hinged elements ready for installation. The roping system automatically opens the hinged panels when lifted. Figure 1.7 shows the roof elements in place, complete with roof-lights and wall ele- ments. The building is now ready for tiling and external brickwork. As the building is watertight, internal work has already commenced.

Figure 1.5 Fuctory-mude hinged roof elements reudy for delivery.

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OFF-SITE FABRICATION

Figure 1.6 Hinged roof elements ready to be installed on-site.

Figure 1.7 Roof elements in place and building basically weather-tight.

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~~

CONTEXT

Alternative roof construction In cases where the hinged roof does not lend itself to a scheme (for example if the degree of repetition is not suitable), another method is to use purlins between the cross wall construction and lay insulated sandwich panels side by side from ridge to eaves. These panels allow for more complicated roof construction with hips, valleys, dor- mers, etc. This type of roof requires more labour than the hinged roof but is still less labour intensive than traditional construction (1 5 work-hours compared to 26 for a conventional trussed rafter roof). The panels have to be counter-battened for the tiles but the advantages are similar: usable roof space, faster build, and an insulated roof instead of an insulated ceiling. Figure 1.8 shows a stack of insulated sandwich roof panels ready for dispatch from the factory. Figure 1.9 shows the roof panels installed (on the right) and the roof structure ready for panel installation (on the left). Cavity wall inner leaf Typically, the inner leaf of the cavity wall is of prefabricated timber-framed construc- tion. This comprises timber panels, a plasterboard inner skin, insulation, all necessary vapour barriers, damp-proof courses, window and door frames (either PVCu or tim- ber), ironmongery, finishing to jambs, etc. Cills, skirting and glazing are included in

Figure 1.8 Factory-made roof panels awaiting delivery

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OFF-SITE FABRICATION I

Figure 1.9 Roof panels instulled on-site.

the cost per mz, but will be built in on-site. Standard joinery, such as that obtained from Danish suppliers for example, is usually delivered to the factory, built in to the elements which are then transported to site as complete units The inner skin can use a material that requires no further decoration, or if required this can also be skimmed and wallpapered or painted. The weight of the wall element is approximately 20 kg/m2. A four-person team plus crane can install 24 elements in four hours Internal walling Because the structure is self-supporting, smooth-faced gypsum internal blocks can be used in their non-load-bearing capacity. The use of these blocks eliminates plastering and thus drying out allowing for earlier decoration. Their application allows for total layout design flexibility. These blocks have better sound and fire resistance properties than stud partitioning (32 dB or 36 dB and minimum 90 minutes respectively). There are two thicknesses 70 mm and 100 mm. The 70 mm block is normally sufficient. There are three types of block:

the regular block; the block with improved sound insulation properties for use between adjoining

bedrooms; a block which has silicone introduced into the manufacturing process to give low

water absorption, which is used for bathrooms.

The blocks can be chased, sawn or drilled and have excellent frictional properties which allow kitchen and bathroom fittings and fixtures to be mounted. Typically one opera- tive would achieve about 50 m2 - or one social house - per day. after setting out has been done. Build cost, using a mix of the various types needed for a typical social type of housing proposed, ranges from about E10 to E13/m2 of wall area, depending upon the geographical region.

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CONTEXT

Door Sets The final item in this rationalised, fast-track concept is the use of doorsets. Pressed steel, factory coated door frames, incorporating architraves with top lights if required, together with pre-painted timber doors, eliminate decoration and reduce maintenance. A wide range of doors and ironmongery is available. A two-person team can install about 80 to I00 sets per day

Cost data A client basically has three options:

Build to an existing design and floor layout using as many of the Dutch materials that the design will permit without major structural changes The suppliers claim that this will lead to savings in time and cost. A good example would be the faster con- struction of the roof using purlins and sandwich panels instead of trussed rafters

Build to an existing design as above but utilise the extra floor area in the roof space. This could be done without major structural changes Again, a faster build time will create savings and more floor space will be created. By using the original floor layout and developing the roof space, the cost per m2 will decrease, however, the overall unit cost will increase (as more floor area is provided) and may exceed the budget.

Build to a fresh design, in terms of internal floor areas and layout, making use of the roof space to create a smaller building footprint. The greatest benefit can be ob- tained from this approach. The smaller footprint uses less land, allows for improved site densities, allows the internal floor area to be adjusted to suit the changed living arrangements with the extra roof space. This also allows the design to be moulded to maximise benefit from the fast-track approach and prefabrication techniques

In the UK, Northern Counties Housing Association is preparing a scheme using the method for 1 17 new semi-detached homes for rent on a brownfield site at Bolsover in Shirebrook, with developer Augusta, and with English Partnership funding. The Dutch method was costed at around &420/m2, giving 33% more floor area per dwell- ing (mainly by utilising the roof space) for an 8.5% saving in building costs over tradi- tional methods

Cost data from a 1997 tender in connection with the requirements of a housing association’s project in the north of England gave the following results.

The project called for the construction of 120 houses, virtually all of which were semi-detached, on a greenfield site. It was originally proposed to build them tradition- ally. After viewing the Dutch houses the client requested the project be tendered on the assumption that the method of construction be adapted in accordance with Dutch practice, but also taking into consideration UK Building Regulations

It was estimated that if traditionally built the project would require a build time of 21 months Using the Dutch method this would be reduced to 12 months Gross usable floor area rose by 33%. The use of a concrete shell understandably incurred a slight cost increase in the foundations however this also had to be weighed against the increased floor area (possible higher rent revenue), possible saving on project financ- ing cost, the earlier availability of the completed houses and the subsequent revenue.

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OFF-SITE FABRICATION

Nevertheless the projected build cost per m2 gross floor area was less than E410. After an initial period of 100 days the first house would be ready for handing over, with an overall completion rate of between four and six houses per week.

Another cost comparison was completed for a scheme with 62 terraced units of varying sizes on a site with difficult access for the Scottish Housing Association, Dunbritton. The original cost plan was based on a build cost of &552/m2 and a con- tract period of 15 months Using the Dutch techniques the build cost per m2 (not including the extra roof-space area) was reduced by 9%. If the roof space had been included the cost would have been reduced by 17%. Site times were also reduced with the concrete shells for the 62 units completed in 12 weeks and the first house ready for hand-over after 100 site days and a hand-over rate of six houses per week.

The following factors influenced the costs of these projects and attention to these aspects will provide further benefits in future:

greater use of terraced layout instead of semi-detached mix higher build rates once operatives are more familiar with the materials and meth-

odology (this refers to the roof and wall elements, internal walling and door sets) future manufacture of some timber-frame elements in the UK will mean a reduc-

tion in the labour cost because of the higher Dutch labour rates and a saving on inter- national transportation cost.

Training In the Netherlands, where most main contractors’ operatives are familiar with the methods and materials, the manufacturers would normally be suppliers only and there would be no need for anything other than a ‘delivered to site’ basis. However, projects outside the Netherlands need a greater input. Therefore all the firms involved offer free training in the Netherlands and site supervision on the project.

Conclusion Dutch practices that have been used for over 25 years offer a rationalised method of house building. It is not ‘new’, and certainly not ‘ground breaking’ by Dutch stand- ards The many advantages are obvious, including the fact that teething troubles have been resolved long ago. The use of tunnel formwork is certainly not new to most countries. However, what is new in the UK is its application to low-rise residential building.

There are variations to this concept, some using different materials However, the thread running through each method remains the same: rationalised building offering more space at a lower cost, an improved performance specification and faster building.

Construction consultant Anthony Redhead explains that these components have been in use for 25-30 years in the Netherlands, are tried and tested, and elements of them can be used in refurbishment. He is aware that some architects are resistant to the idea of a concrete shell and stresses that it can be replaced by normal brick cavity walls with pre-cast concrete floors. However, he points out that ‘a structure whereby the internal walls are non-load-bearing offers many advantages in terms of flexibility for the future.’

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CONTEXT

‘The logistics, planning and drawings have all got to be up front from day one,’ stresses Redhead, ‘then it goes like a train.’ Heat, sound and fire values are main- tained with the concrete shell method. Building times can be reduced by 20-300/0 with typical timings, such as:

complete shells for 2.5 houses a day; installation of timber prefabricated roofs at eight houses per day; timber prefabricated inner leaves to cavity walls at 12 houses per day (two storey

front and rear).

References Ridout, G., 1989; Smit, J., 1996; Clark, L. &Wall, C., 1996; anon, 1996; anon, 1997.

Acknowledgements This case study was compiledfrom information provided by Anthony Redhead of Redex, Construction Export Consultancy, the Netherlands.

Case Study 1.4 Multi-storey residential blocks in Singapore

Singapore, along with many countries throughout the world, has developed effective methods for off-site fabricated precast concrete multi-storey construction. This case study is based on interviews with the Housing Development Board (HDB) of Singa- pore and its presentations at the Kerensky Conference in 1994 (Lau et al., 1994).

In the 1960s HDB set out to provide basic shelter to alleviate an acute housing shortage. In the 1970% the aim was to provide a good housing environment with basic facilities. The 1980s focused on improving the quality of workmanship and finishes, developing communities and creating identity and character of the housing estates In the 1990s and beyond the emphasis has been to provide variety and quality while reducing the construction cost.

Singapore relies heavily on imported labour for its construction industry. An in- crease in construction activity causes a shortage of good quality skilled labour. To cushion this serious impact a continuous effort has been made to use industrialised and mechanised methods of construction in order to reduce the dependency on site labour. HDB developed two basic approaches: the full prefabrication system and the semi-precast system. Both of the systems are similar to those used elsewhere in the world, for instance in Europe, since the 1960s. However, they have learnt from some of the problems encountered in Europe by concentrating on the connections between panels and on quality control of on-site workmanship. HDB’s Lau stresses that, un- like cast-in-place construction, prefabrication requires careful planning right from the beginning of the conceptual design stage.

In HDB’s semi-precast system (Figure 1.10) the main building components such as beams and columns are cast-in-place. Complicated components such as the refuse chute, staircase, parapet and internal partitions are precast.

HDB’s precast-column-beam-slab (PCBS) system (Figure 1.1 1) adds the main struc- tural elements to the list of precast components. A special feature of this system is the four-storey precast column, 12 m long and weighing 12 tonnes These columns, with

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OFF-SITE FABRICATION

1 Floor slab cast in situ 2 Wall cast in situ 3 Precast toilet box 4 Precast refuse chute 5 Precast balcony slab 6 Precast facade wall 7 Precast portal frame

Figure 1.10 HDB seini-precust system with cust in situ structurul beam and column frame system. Adapted from Lau et ul., 1994.

1 Column 2 Beam 3 Slab 4 Parapet

b

Figure 1.11 1994.

Isometric view of HDB PCBS system. Adapted from Lau & Lim,

- 2 6 -

CONTEXT

block-outs for beam connections, are connected together using bolts and splice sleeves The beams are 8 m and 3.3 m long weighing 3.5 and 1 .O tonnes respectively.

Another system employed by HDB is the post-tensioned flat plate floor system (Figure 1.12). This system comprises three-storey precast columns and an in situ con- crete flat slab with no supporting beams which facilitates the use of system formwork. The slab varies in thickness from 160 mm to 200 mm and spans 7.5 m.

HDB have now developed a volumetric bathroom unit, based on a European sys- tem. This unit is fully finished in the factory and comprises a fibre-glass or concrete base with lightweight framing for the walls and ceiling. This keeps the weight to a minimum which facilitates easy installation and site handling.

Lau stresses that the most important concept that must be borne in mind when applying off-site fabrication is the standardisation of building components. Stand- ardisation leads to repetitive sequencing of works, reduces the number of costly moulds during manufacture and speeds up erection work. HDB categorise their components into

components with constant dimensions in all directions components with constant dimensions in two directions components with non-standard profiles and finishes

The HDB have a considerable development programme that enables them to benefit from some economies of scale that were not possible with some of the earlier UK

Building component

1 Precast 3-storey column 7 2 Post-tensioned slab /- 3 Precast parapet

Figure 1.12 Adapted from Lau & Lim, 1994

Isometric view of HDBpost-tensionedflut plate floor system.

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OFF-SITE FABRICATION

Table 1.1 from Lau, 1994.

Degree of standardisation of H D B building components. Adapted

Standardisation Building Component Estimuted Volume (m')

Building components with constant dimensions in all directions

Building components with constant dimensions in two directions

Building components not having standard profiles

Refuse chute Staircase Lightweight partition wall Water tank Plank Parapet wall Gable end wall Beams Columns

Facade

6 500 16 300 15 500

I 900 06 600 20 200 13 500 (Pilot) (Pilot)

28 800

developments Table 1.1 shows the estimated annual volume of each component cat- egory. Acknowledgements This case study was compiled following an interview with C. S. Lim, Housing and Devel- opment Board, Singapore.

Case study 1.5 Multi-storey volumetric modules for Korean high-rise residential buildings

The Daewoo multi-room modular construction system is a volumetric precast concrete system for multi-storey construction. A typical project has a four-month mobilisation period when a prefabrication facility is set up on the project worksite (On the develop- ments in Korea, there has been enough space on-site to accommodate this) Figure 1.13 shows a development site with the precast facility in the background and the site craneage installing units.

The precast concrete modules are manufactured (see Figure 1.14) and then crane- lifted into position at a rate of one floor per day. Daewoo claim that their system is two to three times faster than conventional methhods The interiors are then fitted out using factory built panellised walls incorporating mechanical and electrical works. They claim a lower overall project cost due to high labour productivity, savings in material costs, savings in overhead costs; and fewer construction problems such as control of safety hazards or pollution. The system is designed to be used to any height, with typical buildings exceeding 15 storeys.

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CONTEXT

Figure 1.13 Courtesy of Daewoo Corporation.

View of typical site layout showing on-site prefabrication facility

Figure 1.14 Corporation.

Typical unit in the prefabrication facility. Courtesy of Daewoo

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OFF-SITE FABRICATION .. .”” . - . ,. , , h,_ , . , ..

Figure 1.15 Courtesy of Daewoo Corporation.

One of 168 two-bedroom units being installed on a 12-storey block.

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Barrick, A., 1995. Arrested Development. Building, 21 April, The Builder Group, London. Bender, R., 1993. A crack in the rear view mirror: a view of industriulisedbuilding. Van Nostrand

Broberg, l? 1986. The evolution of industrial building. Design Studies, 7. Butterworth & Co. CIRIA, 1997. Snapshot - Standardisation and Pre-assembly. Groak, Gibb & Sparksman,

Construction Industry Research and Information Association, London, 1-8. Chevin, D., 1993. Car chase. Building, The Builder Group, 10 December, 36-37. Clark, L. & Wall, C., 1996. Speed building Almere, Holland. World Architecture Housing,

October, 132-33. Coaldrake, W, 1986. Manufactured housing: the new Japanese vernacular. The Japan Archi-

tect, 8608, 60-67. Gibb, A.G.F., 1996. Vintners Place: procurement, design development and construction of a

complex building facade with a traditional appearance. Proceedings of the Institution of Civil Engineers, Structures & Buildings, 116 (l), 96-108.

cember, The Builder Group, London.

Reinhold Company, New York.

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Groik, S.. Bottom, D., Gann, D. & Meikle, J., 1996. Introwtion in Jupunese prejibricuted house building industries. Department of Trade & Industry OSTM visit report, ClRIA SP139, Construction Industry Research and Information Association, 66 pp., ISBN 0 8601 7 463 8.

Croak, S., 1992. The irleu of biiilrling - tlrouglit N I K I action in the design uncl production of buillirrgs. E. & F N. Spon.

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Kjeldsen, M., 1988. l~ i~l i i . s t r i~ i l i . se~l l t~~i i . s i~~g in Dennturk. Danish Building Centre Group, ISBN 87 503 71762.

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Matsudome, S. I., 1990. Japanese prefabricated timber house construction. Hubitat Interna- tional, Pergamon Press, 14, (2/3), 263-266.

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Thompson, J. D. & Goldin, G., 1975. The Hospitul: a sociul and arclritecturul history. Yale University Press.

various, 1995. Design for living. Building Hornes, The Builder Group, 24 March, 23 pp. Weeks, S. J., 1981. Hospitals. Architects Journal, 7 January. White, R. B., 1965. Prefabricution - A history of its development in Great Brituin. HMSO,

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London.

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