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Facing up to interfaces

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technical & practice

The Egan Report offers what it calls a 'practical approach' to increasing efficiency and quality. This includes developing buildings as generic products, and producing discrete components, but it does not cover the use of construction materials.

The report says that there is no reason why the approach to component production within construction should be radically different from that used by leading manufacturers of consumer products.

However, materials are as essential to building construction as discrete components, and the use of materials puts technological barriers in the way of the transfer of consumer product manufacturing approaches.

A previous article (aj 18.11.99) explained how demand for buildings which do not have fixed forms and finishes also results in technological barriers to the transfer of key manufacturing systems. Such systems have made it possible to increase the variety of consumer products, and reduce manufacturing times and costs.

An essential step in overcoming these barriers is for chartered architects to collaborate with suppliers and trade contractors in developing a universal construction 'product architecture'.

The term 'product architecture' is used by consumer-product designers to define how the functions of a product are arranged into physical components.

Fundamental differences between consumer products and buildings make construction without the use of materials impractical, but the use of materials results in technological barriers to the transfer of consumer product manufacturing approaches. I have suggested below an updated construction product model with a component structure which includes materials.

Building designers are usually employed to create patterns of space which deliver the specific functionality required by a specific customer. This contrasts with the work of car designers, for instance, who create a standard space which delivers the general functionality required by a customer type. This enables car designers to fix the form and finishes of each car model.

But even if a specific client, such as a hotel chain, instructs an architect to design a standard building for repeated construction, forms and finishes cannot always be fixed because a building encloses a specific space which is defined by its specific location. For example, the footprint of a building is constrained by location-specific factors, such as adjacent structures and natural features. Similarly, the colours and textures of its finishes are constrained by planning laws which are intended to ensure that existing environmental characteristics are respected. There are also often significant differences between the dimensions of a building and the dimensions shown on its construction drawings. All of these factors restrict opportunities to fix the forms and finishes of buildings.

Consequently, materials, such as vinyls, adhesives and sealants are used to construct building details that cannot always be achieved by discrete components, such as shower trays, which have fixed forms and finishes. Also, materials, such as plasterboard, plaster and paint are used to provide a coherent appearance for irregular interfaces between discrete components, such as square ceiling tiles and curved curtain-walling sections. These are some of the reasons why materials are essential to the construction of buildings.

Under the heading, 'Promising Developments', the report of the Construction Industry Task Force, Rethinking Construction, differentiates between components and materials. But materials are not included in its 'practical approach' for delivering increased efficiency and quality.

Although the Task Force differentiates between materials and components, in the manufacture of discrete products, it is materials which begin a fixed vertical-component hierarchy which ends with the product.

Table 1 provides two examples.

Where the forms and finishes of a product are fixed by the manufacturer, the forms, finishes, configurations and interfaces of that product's components can also be fixed. It is then feasible for the manufacturer to design the product so that only discrete components (those shown in levels 1, 2 and 3 of Table 1) are needed for product assembly and use. Where demand for the product is high it is then viable for the manufacturer to invest in the production of these discrete components.

It is neither feasible nor viable for manufacturers to develop discrete components that can cater for all the dimensional and aesthetic irregularities that are inevitable in the construction of buildings that do not have fixed forms and finishes. Therefore, it seems likely that buildings that do not have fixed forms and finishes will continue to be constructed with conventional materials, as well as discrete components.

Thus, for both component manufacture and component assembly, there will continue to be fundamental differences between designing and planning the production of a new car model, and designing and planning the construction of a new building.

The report defines project implementation as being about translating the generic product into a specific project on a specific site for a specific customer. However, leading manufacturers do not 'translate' a 'generic product' when they receive an order. They generate order-specific manufacturing information by using computerised systems, such as mrpii (Manufacturing Resource Planning), to perform standard configurations of standard component data.

The use of materials in construction results in barriers to configuration standardisation. This is because the construction of buildings which do not have fixed forms and finishes relies upon materials being placed with installed parts in the sets of component relationships in Table 2.

In contrast to discrete products, these construction component relationships are neither vertical nor fixed. This limits opportunities for transferring the benefits of mrpii systems into the construction industry.

Also, standard mrpii component data are linked to standard procurement and resource schedules which minimise waste of materials, plant and labour time. However, buildings which do not have fixed forms and finishes have irregular interfaces between discrete components. This limits opportunities to standardise material data without including significant allowances for waste. This is not compatible with 'lean thinking'.

Product architecture is concerned with arranging the functions of a product into physical components. But both formless and formed materials are as essential as discrete components in delivering the particular functionality required by each construction client. Table 3 below shows an updated version of the product model introduced in our first article.

It now includes a proposal for a component hierarchy and configuration structure which includes both discrete components (parts) and materials.

Comments on this product model to prodmod@hammal.co.uk. Stephen Fox is director of Hammal. Graham Cockerham is professor of engineering design at SheffieldHallam University.

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