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2.2 Attributes of good quality production drawings

2.2.1 Spatial and technical coordination

The same element, component or product should correspond in shape, size, spatial position and designation when shown on different drawings. 'Clashes', i.e. different items occurring in the same or overlapping position, or impinging on the clearances required by others, must be avoided – this is a particular problem with building services. Ducts and other service routes must be of adequate size, and must allow for suitable access for installation, maintenance, repair, adaptation and eventual replacement of the services.

Even on a small project, with all the drawings prepared by one person, errors and discrepancies can occur. On a large project, with many design personnel and several design disciplines working separately, coordination is a major issue.

Figure 2.1 Services clashing with structure

Every element, component and product must be positively located in three dimensions, either by its clear relationship with grid lines, or by figured dimensions. Dimensions should fit with and be consistent with other associated dimensions.

2.2.2 Drawing types and their content

The content of drawings should be correct, complete and easy to assimilate. Fragmentation of information can easily lead to parts of it being overlooked. In so far as is practical and commensurate with ease of use, needless duplication of the drawn information is to be avoided so as to reduce the likelihood of discrepancies arising in the course of revision. Both duplication and fragmentation of the information can be minimised by consistent use of the following 'functional' types of drawing:

General Arrangement drawings: These should enable users to:

• Gain an overall picture of the shape, layout and form of construction of the building and external works;
• Determine setting out dimensions;
• Locate and identify the spaces and parts of the building, e.g. rooms, doors, structural frame members, services terminals;
• Pick up references to more specific information, particularly to assembly drawings.

Assembly drawings: These should enable users to:

• Determine how parts of the building and their junctions are constructed;
• Pick up references to more specific information, particularly to the specification and any component drawings.

Component drawings: These should give information about components that cannot be given adequately on the assembly drawings.

2.2.3 Annotation of drawings

The production drawings generally give information about size, shape and location of the various types of work, features and parts of the building, but these have to be identified in order to make the drawings intelligible for purposes of construction. Drawing titles should help to identify the content of drawings (see Section 2.2.6 below), but written annotation within each drawing is also necessary.

Some items of annotation will be to clarify the graphic and location information given on the drawing itself, e.g. 'Existing ground level', or 'Room 103'. But the purpose of much annotation is to identify and refer to related information given elsewhere, there being two types:

• References to other drawings;
• References to the specification document.

Written information on drawings is often the cause of poor coordination because, when making revisions, it can be difficult to ensure that all affected drawings are changed. Annotation should therefore be put on drawings only for good reason, and if there is not a good reason it should not be given.

Where drawings contain a number of different views of the same piece of work, some repetition of annotation is unavoidable. However, if the set of drawings has been carefully planned and arranged, problems arising from revisions will be minimised.

References to other drawings

Drawing references should be to a particular sheet and preferably to a particular view or detail on that sheet. Imprecise referencing such as 'see engineer's drawings' or 'to be read in conjunction with all relevant drawings' are of little or no use.

Ease of use and confidence in the information are more likely to result if the references display a logical pattern of links between the drawings in a set. Almost all references should lead from general arrangement drawings to assembly or component drawings. The locations at which larger scale details apply should be clearly shown by section cut lines or circles on the general arrangement drawings.

BS ISO 128 deals with such matters as referencing and standard symbols.

Specification references

It is impractical to give full specification information in the form of annotation on the drawings. Abbreviated specification information given on the drawings will, at best, duplicate information given in the specification document. At worst it will conflict with the specification, or lead the constructor to act without referring to the specification.

It is therefore recommended that specification information be given only in the specification document, and that drawings identify the different kinds and items of work, but do not specify them. This should be by using a few carefully chosen words (the minimum necessary for unique identification) with, as appropriate, a reference to the relevant clause or item in the specification document. This principle applies to both larger projects using a specification (see Section 3.3.2) and smaller projects using a schedule of work (see Section 3.3.3).

Where a specification (rather than a schedule of work) is used, the annotation should provide minimal, yet sufficient. For example in the case of floor joists:

• What is it, e.g. joists?
• What is it made of? Is it necessary to state this to uniquely identify the item? The term 'softwood' may be considered superfluous. However if some joists are sawn, others wrought, it will be necessary to state, e.g. 'sawn softwood'.
• Is there any other distinguishing feature, e.g. some structural timbers may be preservative treated, others not. If so, it will be necessary to state, e.g. 'treated'.
• What size are they, e.g. 200 x 50 mm?
• At what centres, e.g. 400 mm?
• What is the reference to locate more specification information, e.g. G20/102?

The appropriate annotation may therefore be '200 x 50 treated joists at 400 centres G20/102'. The rest of the specification information such as type of treatment and type and grade of softwood can be found by following up the reference to the specification.

In most cases selecting the appropriate annotation will be simpler than in the above example, e.g. 'Urinal and cistern N13/130' (see Appendix S2). Further information and examples of referencing to a specification are given in Section 4.1.5.

Where a schedule of work is used, the nature of the annotation will be different. The references should be to the 'construction' headings in the schedule of work, and should not duplicate any of the detailed information given under those headings. Further information and examples are given in Section 5.1.4.

2.2.4 Arrangement

On larger projects the arrangement of a set of drawings has a major influence on user comprehension and the ability to retrieve information. In general, the larger and more complex the project, the more important is the arrangement of the production drawings. On smaller projects (with up to say 20 drawings) arrangement is far less important, particularly if the titles of the drawings are concise but helpfully specific, and there is specific cross-referencing from general arrangement drawings to details.

The essence of good arrangement is the division of the whole set of production drawings into easily recognisable groups, with an overall structure that is simple and easy to memorise. It is vital to remember that although the drawings may have been produced electronically, for most of the time they will be stored and used on site in paper form. Whatever arrangement is adopted, it should be set out clearly in the Drawings Register (see Section 2.4.3).

Grouping of the drawings may be by any one or more of the following:

Grouping by office of origin

It has long been common practice to use office of origin as the primary grouping for sets of drawings, and constructors have become accustomed to the type and style of information to expect from each of the design offices. However, when using CAD systems differences in style and format between the drawings produced by different offices, especially fonts and line styles, are not always transferable between systems. This is particularly true when converting into read only formats, which will often only accept True Type fonts.

Grouping by office of origin is primarily one of convenience for the design consultants rather than to help the constructor find information, and although it is well established, there is increasing reason to doubt the wisdom of it's continued use:

• There is a strong case for using 'type of information' (see below) as the primary arrangement for sets of project drawings. This is particularly so if two different sizes of drawing sheet are used, say A1 for General Arrangement drawings and A2 for Assembly and Component drawings, so that filing of the complete project set in cabinets on site will be facilitated.
• It is true that 'office of origin' usually corresponds generally with the main parts and systems of the building, but if such a grouping is desired it can be achieved more effectively by using a 'parts of building' grouping (see below) or by 'blocking' of sequential numbers (see Section 2.2.6 below).

Ownership of information is very important – firms are accountable for the information they supply. Audit trails must be maintained whether firms issue paper drawings, or their electronic equivalents and the 'model' files from which they were derived. With electronic information, ownership is typically identified at both the layer name and file name level, and finished drawings often have more than one 'author'.

Notwithstanding the above, the procedures recommended by this Code do not prevent grouping by office of origin if so desired by the design team, provided that the overall arrangement of the set is clear, simple and convenient in use.

Grouping by type of information

This is also well established in practice, the main categories being:

• General Arrangement (plans, sections and elevations);
• Assembly (details of junctions between parts and products);
• Components (pre-assembly).

There is considerable flexibility to the classification, particularly because the categories follow the user's normal search sequence. Searches usually start with the General Arrangement drawings, which if necessary will refer to supplementary Assembly drawings. The latter need only be produced when the General Arrangement drawings need amplification. Component drawings need be produced only when the Assembly drawings are not sufficient to define a component.

The General Arrangement drawings are often produced on large sheets of paper (A1 or A0), and the Assembly and Component drawings on a smaller size (A2 or A3). The convenience of filing all drawings of the same size together indicates that 'type of information' is likely to be chosen as the primary grouping for the set of project drawings. On smaller projects it is likely that the only grouping needed will be General Arrangement and Assembly drawings.

Grouping by parts of the building

On larger projects the number of drawings in the groupings described above can be considerable, and subdivision of at least some groups may be desirable. The major common factor between producers and users of drawings is the building itself so that sub-grouping drawings by the parts of the building they define has proved effective in practice. A standard list of elements should be used, Uniclass Table G, Uniclass Table H, or CI/SfB Table 1 (see Appendix D2).

However, if a separate drawing is produced for every separate part of a building, the result can be a mass of fragmented information. This can be avoided by:

• Where appropriate using the higher level classifications of the chosen elements table, and/or
• Classifying details by their predominant parts. For instance, a roof edge drawing may show information about wall, ceiling, drainage, etc, but if the predominant information is about the roof, then it should be grouped with the roof drawings.

Where the General Arrangement and/or Assembly drawings merit division into elemental sub-groups, these can be chosen to suit the major specialist works included in the project. Examples include piling, structural frame, curtain walling, suspended ceilings, partitions, lighting and power, HVAC, lifts, security, culinary equipment, soft landscape, etc.. Specialist constructors should be required to produce their detailed design or shop drawings so that they fit seamlessly alongside the consultants' drawings into the overall project set.

Grouping by location

The plans for some projects will not fit at a suitable scale onto one drawing sheet, and the site or building must be split into zones or blocks. As far as possible the boundaries of these should occur at natural construction breaks where little information is needed. The effect of such zoning on the arrangement of the project drawings will depend on the nature of the design:

• If the zones or blocks are completely or almost completely independent and have different designs, each can be considered as if it were a separate project and sub-divided into other groups.
• If the layout of the zones or blocks differ but their detail design is similar, some other grouping (e.g. General Arrangement, Assembly, Component) should take precedence. The zones or blocks can then form identifiable sub-groups of, say, the General Arrangement drawings only.
• If the layouts of the zones or blocks are substantially the same, creating 'standard' location drawings can avoid unnecessary repetition. Examples of this are drawings for house types or factory unit types.

Keep it simple

The various types of grouping described above should be used with discretion, avoiding over-elaboration. It is vital to make the overall arrangement reasonably simple and easy to comprehend, and to keep the related drawings numbers fairly short (see Section 2.2.6 below).

2.2.5 Sheet sizes and scales

Sheet sizes and scales are obviously inter-related, and can have a major effect on arrangement of the set of production drawings.

Sheet sizes

To facilitate handling, reference and storage it is desirable that the sheets within any group of drawings are of the same size. The use of one sheet size for the whole project set is often suitable but, because it enables easy identification of different groups, consideration should always be given to using two sizes, e.g. A1 for General Arrangement drawings and A2 for Assembly and Component drawings. Standard sizes are:

Scales

The choice of scales should:

• Permit clear interpretation of the data. For example, a 1:100 plan may be satisfactory for general layout and providing references to other drawings, but if setting out of brickwork, etc. is to be shown 1:50 may be preferable.
• Permit easy comparison of information, e.g. General Arrangement plans showing different things should, if possible, be to the same scale.
• Be such that the user can refer directly from General Arrangement drawings to Assembly drawings. Intermediate scale drawings should be avoided if possible.
• Be determined by the requirement for clarity of the information rather than, for example, wishing to keep all sheet sizes the same.

2.2.6 Drawing numbers and titles

Numbering

The purpose of numbering is to give each drawing a unique place in the set to facilitate filing and retrieval. Drawing numbers usually fall into three parts:

• A project identification number - this is useful for office purposes, but is normally ignored for communications within the project.
• A classification group identifier, e.g. A for Assembly drawing or 24 for Roof drawing (Uniclass element). On larger projects two classification group identifiers may be warranted, e.g. A/24.
• A sequential number giving unique identification within the classification group number.

The most commonly used classification grouping is the type of information, i.e. General Arrangement, Assembly and Component, for which the mnemonics G, A, and C are recommended. On larger projects, where a 'part of building' classification is warranted, numbers from Uniclass Tables G or H or CI/SfB Table 1 may be used. These elemental classifications can be used for both general drawings (e.g. 20 building fabric as a whole) and specific drawings (e.g. 23 stairs).

Ad-hoc classification numbers are sometimes used e.g.:

• Office of origin - A for architect, S for structural engineer, E for electrical engineer, M for mechanical engineer, etc.
• Location unit - House types 1, 2, 3 etc. or Blocks A, B, etc.

Classification numbers can be very useful if used sparingly and selectively, but if more than one or two are used in any particular combination the drawing numbers will be too complicated. Classification numbers should not be allowed to influence the selection of the drawings to be produced – the result can be a proliferation of over-specific drawings causing difficulties in interpretation and coordination. Decisions about the use of classification numbers should be taken after the decisions about drawing grouping.

Sequential numbers should follow any classification numbers, and will most commonly be of two or three digits. They should be arranged in 'blocks' to give useful sub-groupings of drawings, and can often be used to represent classification groupings without the complication of using the standard classification numbers, for example:

• Type of information (for a small project): 01 –29 General Arrangement, 30 – 59 Assembly, 60 – 79 Component, 80 – 99 Specialists' drawings.
• Office of origin: G/001 – G/099 architect's General Arrangement drawings, G/100 – G/199 structural engineer's, G/200 – G/299 services engineer's, etc.
• Location: G/001 – G/099 site layouts, etc., G/100 –G/199 General Arrangements for house type 1, G/200 – G/299 house type 2, etc..

Assembly drawings normally contain several details, and it is good practice to number each detail as if it were a separate drawing, to facilitate cross-referencing. A typical Assembly drawing sheet might thus be numbered A/210 – 215.

As with the arrangement of drawings the over-riding principle should be simplicity and clarity. Numbers should strike a balance between being informative and being easy to comprehend. To help achieve this the different 'fields' within drawing numbers should be separated visually, e.g.:

• G/101 (General Arrangement/sequential number).
• G/21/101 (General arrangement/Uniclass element/sequential number).
• G(16)101 (General arrangement/CI/SfB element/sequential number).

Titling

Even when sets of production drawings are well arranged and helpfully numbered, rapid and certain information retrieval is, to a considerable extent, dependant on effective titling. Titling should:

• Achieve a good balance between brevity and identification of the contents.
• Use consistent terminology, e.g. 'zone' or 'block', 'plan' or 'layout'.
• Use terminology consistent with other documents, e.g. by using CAWS terminology wherever possible.

Drawing titles should normally be sufficient to answer the following questions:

• Where does the information apply, e.g. generally, Block B, first floor, kitchen, etc.
• What type of information does the drawing contain, e.g. General Arrangement, Assembly, Component.
• What type of drawing is it, e.g. plan, section, elevation, schematic, details, etc.
• What features does the drawing show, e.g. steelwork, concrete bases, roof details, planting layout, etc.

2.2.7 Drawings issue and revisions

Whilst constructors are used to managing projects using paper based information, issuing drawings in a suitable electronic format can be very useful as they are more easily reused and distributed. The copying, folding and distribution of paper drawings to specialists is labour intensive, and if the constructor can distribute drawings electronically, much time is saved.

There will often be pressure to issue drawings before they are complete. Issuing a drawing before it contains the information required to meet its purpose should be resisted. Comprehensive checking and approval should always be carried out before issue to ensure that subsequent revision is minimised.

Revisions arise for many reasons, e.g. changes in client requirements, addition of information not previously available or correction of error. Whatever the reason it is essential that they are implemented and communicated in a controlled manner.

In principle all drawings affected by a revision, including drawings by other designers, should be brought up to date as soon as the change has been agreed. In practice, during the design phase, too frequent issuing of updates that reflect only minor changes can interfere with the logical progress of the work and increase drawing costs unnecessarily. However, delay in issuing updated information can cause abortive design work and increase construction costs significantly. A balance has to be struck and the significance and urgency of the information should be considered before issue.

When a drawing is revised, a short but comprehensive description of the revision, and its date, should be added under consecutive revision letters within a space adjacent to the title panel. Wherever feasible, some graphic means should be used to identify the location of the revision on the drawing.

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