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1.19 The simplest possible sub-division of building structure 1.20 Sub-division of building structure into structural elements this is an over-simplification, and that a minimal sub-division of elements would look much more like 1.20.

The elements here have one common feature—they are all structural. We may introduce other elements, but it is apparent that we are then setting up another hierarchy of information analogous to the hierarchy established when considering types of information (1.21).

It is one thing to recognise the existence of this hierarchy, and another thing altogether to set it down in simple and universally acceptable terms. The trouble with hierarchic systems—in building communications as in politics—is that they tend to be complex, difficult to understand and self-defeating when applied too rigidly. Their great advantage—in building communications at any rate—is that they offer the user access, at the level most appropriate to his purpose. So we are looking for a method of elementalising the building which fulfils the following requirements:

• It should be simple to understand

• It should be universally applicable

• It should operate on a number of levels, permitting a greater or lesser sub-division of information depending upon the size and complexity of the building in question.

Home-made systems: It is not difficult to devise your own systems to meet these requirements. Indeed, in practice many offices do, varying the method each time to suit the complexity of the job in hand. Within the overall primary location/component/assembly framework, for instance, to divide the drawings on a small project into, say, brickwork (series B), windows (series W), doors (series D) etc might be one such method. The precise method of sub-division and of coding is less important than recognising the existence of an inherent primary and secondary structure.

CI/SfB

A fully developed method is readily available, however, which fulfils most of the requirements of an elemental secondary structuring system, and which has the advantage of being already well-established for other purposes. This is the CI/SfB method of information classification and, while it has its detractors, who legitimately point to certain weaknesses in detail, it has so many advantages that on balance it must be recommended. Certainly it forms the basis of most of the drawings illustrated in subsequent chapters. Its virtues are:

It is one of the two most widely known and used classification methods available to the building industry. (Its rival, the Common Arrangement, has substantial defects for architects which will be referred to later.)

It is comprehensive in its scope, offering opportunities for uniting the drawings (with their emphasis on building elements) and the specification and bills of quantities (with their emphasis on materials) into a common terminology.

It is capable of operation at various levels of sophistication, making it suitable for both large and small projects.

It is compatible with use of the National Building Specification.

It is the method forming the foundation of the Co-ordinated Project Information concept. It is compatible with the use of computer aided draughting.

It is compatible (subject to some modification) with advanced developments in computer technology allowing the electronic exchange of drawings between design offices and building site.

The complete CI/SfB system is undoubtedly complex and many people shy away from it, frightened at the prospect of having such a sophisticated sledge-hammer to crack such small nuts as are the mainstay of the average practice. This is a pity, for that aspect of CI/SfB which is of greatest relevance to the drawing office is in fact of a disarming simplicity. (It is certainly less complicated than some home-made systems that one has encountered over the years.)

1.21 Further sub-division of the fabric leads to increasing complexity

Before looking at this aspect in detail, however, let us look briefly at the whole range of the CI/SfB system of classification.

There are five tables in the complete CI/SfB matrix (see box below).

All of these tables are used for library classification; and indeed it is possible to use them in addition as a framework for complete project documentation, upon which every site, drawing office and administrative activity may be fitted. But this is better left to the doctrinaire, the highly ambitious, or the managers of extremely large and complex projects, where the organisational requirements are so great that they may well benefit from such an approach.

In general terms of drawing classification, we may safely discard tables 0 and 4 as being irrelevant to our

CI/SfB—The Complete Matrix

Table 0 dealing with physical environment. Such subjects as housing, hospitals and other building types etc come under this heading, and the code is always of the nature Bl.

Table 1 dealing with elements—stairs, roofs, ceiling finishes etc. The codes are always bracketed, in the form (24), (27), (45) etc. Table 2 dealing with the constructed form of products, ie manufactured components. Typical examples would be blockwork—blocks (code F), tubes and pipes (code I) or thin coatings (code V). The codes are always a single upper case letter. Table 3 dealing with materials—ie the basic materials from which the manufactured components of table 2 are made. Examples would be:

gypsum (code r2)

flame-retardant materials (code u4)

The codes consist of a single lower case letter, usually with a single digit as sub-divider, and it will be seen that, when used in conjunction with the codes of table 2, they provide a method of shorthand for quite specific descriptions of components:

blocks in lightweight aggregate Fp3 clay tiles Ng2

plywood Ri4

Table 4 dealing with activities and requirements. In other words, the various techniques involved in the physical process of building, such as: testing and evaluation demolition.

The codes for these would be, respectively, (Aq) and (D2)

It should be noted that these codes become slightly more complex when dealing with computer technology. The differences are outlined briefly in the section dealing with computer draughting.

purpose, set aside tables 2 and 3 for later, when the question of correlation between drawings and specification is being considered, and concentrate our attentions on table 1, which is given in its entirety as Table II (p 20).

CI/SfB table 1: Its hierarchic structure is immediately apparent. Within it each building element may be considered at any of three levels, the level selected being determined by the complexity of the project in question and the need to break down the conveyed information into categories of manageable size. Any element within the building—a lavatory basin, for example—may clearly be regarded as forming part of 'The project in general (—)'. But it may also be considered as coming within the category of 'Fittings (7-)' (the seventh of the nine vertical columns into which the table is divided). Or, finally, it may be regarded as coming within the quite specific grouping of 'Sanitary, hygiene fittings (74)', the fourth horizontal sub-division of column (7-).

Windows, in similar fashion, may be seen as coming within the (—), (3-) or (31) headings, terrazzo tiles as (- -), (4-) or (43). And so on.

The primary and secondary information structure is therefore complete, and we are ready to move on to detailed consideration of what each drawing should contain and what it should attempt to convey to the recipient. Before doing so, and since the seventy-five possible facets of table 1 can be a pretty daunting prospect, it may be encouraging if the following points are made:

1. The only possible justification for structuring a set of drawings is that it makes life easier for everybody to do so. The moment this ceases to be the case, the system becomes self-defeating and you would be better off without it.

2. When we talk of elementalising the drawings we are in effect talking exclusively of the location drawings. These are the only drawings which will be drawn elementally in the sense that the same floor plan, for example, may be shown several times to illustrate the

Table II CI/SfB Table 1

(—) Project in general

Primary elements

(3-) (4-) Secondary elements Finishes

External, other elements

(10)

(20)

(30)

(40)

(50)

(60)

External works

(11) Ground

Secondary elements to external walls

Wall finishes, external

Circulation, loose equipment

(91)

Secondary elements to internal walls

Waste disposal, drainage

Rest, work loose equipment

Culinary loose equipment

(93)

Sanitary, hygiene loose equipment

(94)

Space cooling

Cleaning, maintenance fittings

Cleaning, maintenance loose equipment

Retaining walls, foundations

(26)

Storage, screening loose equipment

Pile foundations

Air-conditioning, ventilation

Special activity loose equipment

Building frames, other primary elements

Security, control, other services

Parts of (11) to (19), cost summary

Parts of (21) to (29), cost summary

Parts of (31) to (39), cost summary

Parts of (41) to (49), cost summary

Parts of (51) to (59), cost summary

Parts of (61) to (69), cost summary

Parts of (71) to (79), cost summary

(89) Parts of (81) to (89) cost summary

(99) Parts of (91) to (99), cost summary

various elements contained within it. All other categories of drawing—assembly, component, subcomponent, schedule—will fall within one or other of the elemental sub-divisions: but they will be drawn once only and will appear once only in the drawing set.

3. Although all the facets of table 1 are available, like so many pigeon-holes, to receive the various drawings prepared, there is no particular virtue in trying to use them all. In practice a very few will suffice, even for the largest projects. Never forget the two-fold objective of this secondary structuring, which is to provide both a disciplined framework for the draughtsman and a simple retrieval method for the seeker after information. A drawing set containing a couple of drawings in each of some thirty elemental sub-divisions assists the achievement of neither.

4. Given a true understanding of the objectives, common sense is the paramount consideration.

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