Complete Drawing Details Of A Precast Concrete Building

Component sub-component and assembly drawings

Component drawings

A component may be defined as any item used in a building which emanates from a single source of supply and which arrives on site as a complete and self-contained unit, whose incorporation into the building requires only its fixing to another component or components. Thus, a window is clearly a component, as is a manhole cover, a door, a section of pre-cast concrete coping, a mirror. So, for that matter, is a brick. (A brick wall would be an assembly.)

Two types of component should be distinguished:

1. There is the manufacturer's product, available off the builders' merchants' shelf, for which no descriptive drawing need be prepared. Such items as standard windows, sanitary fittings and proprietary kitchen units may be described uniquely by the quotation of a catalogue reference. If they are to be drawn at all then their draughting will be in the simplest terms, more for the avoidance of doubt in the minds of architect and contractor than for any other reason. Certainly any detail as to their method of construction will be at best redundant, and at worst highly amusing to the manufacturer.

2. There is the special item requiring fabrication—the non-standard timber window, the reception desk, the pre-cast concrete cladding panel—and in order that someone may make it as required, it is necessary for the architect to define quite precisely what it is he wants, and (in many instances) how he wants it to be made.

Clearly it is the latter category that is of most concern at the drawing stage.

In both categories, however, a basic principle holds good. The component in question should always be defined as the largest single recognisable unit within the supply of a particular manufacturer or tradesman. An example will make this clear.

Figure 3.1 shows an elevation of a row of fixed and opening lights, contained within a pre-case concrete frame, and separated from each other by either a brick panel or a pressed metal mullion. How many window components are there? We may look at this in various ways, and all of them would have some logical force behind them. We could say, for example, that there were six window components of which four were of type A and two were of type B (see 3.2) . There is an attractive simplicity about this view.

It could be argued with equal justification, that we had in fact a single component, consisting of an assemblage of fixed lights, opening lights, coupling mullions and brick infill panels. The component, in fact, is everything held within the overall pre-cast concrete frame (see 3.3). This approach too has its attractions.

The correct procedure, however, will be to regard the whole assembly as consisting of two window components (3.4).

The key determining factor here is the supply of the component. It is reasonable to make the window manufacturer responsible for supplying the pressed metal coupling mullions, but not for supplying the brick panel—and if he is to provide the coupling mullions, then it is rash and unnecessarily intrusive for the architect (inexperienced in this field) to take responsibility for the assembly junction between light and mullion. One of the problems associated with an increasingly factory-oriented building technology is ensuring a satisfactory fit when two components of different manufacture come together on site. Treating the component as embracing the coupling mullions at least puts one aspect of the problem squarely on the shoulders of the window manufacturer, who is best equipped to deal with it.

This principle may be extended with advantage. If doors and frames are treated as two separate components the responsibility becomes that of the architect to ensure that the door meets the frame with the correct tolerances. If, however, the component is regarded as being the complete doorset, then

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