Last edited 02 Nov 2016

Types of drawings for building design

See also: Design drawings for a description of the development of drawings through project stages.

Contents

[edit] Location drawings and general arrangement drawings

The information shown on a locating drawing will be overall sizes, levels and references to assembly drawings. They are intended to show the location of the works, not detail (a common mistake). The location drawings, which can be plans, elevation or sections, are numbered consecutively with the prefix L.

Typically, location drawings will include:

British Standard Specification 1192 includes recommended or preferred scales for location drawings.

[edit] Block plans

Block plans usually show the siting of the project in relation to Ordnance Survey Maps. Conventions are used to depict boundaries, roads and other details. Recommended scales are:

  • 1 : 2500
  • 1 : 1250
  • 1 : 500

Typical location plan.png

[edit] Site plans

Site plans usually show the extent of the site but no surrounding detail. Recommended scales are:

  • 1 : 500
  • 1 : 200

The function of the site plan is to show:

  • The location of the building or buildings in relation to their surroundings.
  • The topography of the site, with both existing and finished levels.
  • Buildings to be demolished or removed.
  • The extent of earthworks, included, cutting and filling, and the provision of bank and retaining walls.
  • Roads, footpaths, hardstandings and paved areas.
  • Planting.
  • The layout of external service runs, including drainage, water, gas, electricity, telephone, etc.
  • The layout of external lighting.
  • Fencing, walls and gates.
  • The location of miscellaneous external components – bollards, litter bins, etc.

Typical site plan.png

[edit] Floor plans

Floor plans usually show the layout of rooms, key dimensions and levels, and may also use conventions and symbols to show materials and locations of fittings and appliances. Recommended scales are:

  • 1 : 200
  • 1 : 100
  • 1 : 50

Line types are used to differentiate information in floor plans. Hatching or conventions are used to illustrate materials, while symbols are used to show fittings and appliances, often with standard abbreviations.

Typical house ground floor plan.png

There are three situations that must be considered:

  • General arrangement (location) drawings designed to show a single building element and what it should contain.
  • General arrangement drawings designed to be complete in themselves (clearly this type of drawing would only arise on the smallest and simplest of projects.)
  • Basic floor plan drawings – the drawings which provide the fundamental and minimal information which will appear as the framework for each individual elemental plan. The basic drawing, in fact, from which future drawing containing elemental information will be taken.

[edit] Basic floor plan

If a set of working drawings for a project is prepared, the floor plans may be divided into five elements in the following manner:

(2-) Primary elements

(3-) Secondary elements (5-) Services (piped and ducted) (6-) Services (electrical) (7-) Fittings

[edit] General arrangement plans

Where the elemental plans are to be drawn by CAD or manually, you must fist consider what common features of the plans will need to appear in all five elementalised plans given in the example above. It is clearly important that the information carried by the base negative, (manual) or layers common to all drawings in a CAD set shall be, not too little, and not too much. Below is a check list of what the basic plan should contain and a list of those items which more often than not get added to the original needlessly and superfluously to the subsequent inconvenience of everyone.

To be included:

  • Walls
  • Main openings in walls (i.e. doors and windows)
  • Partitions
  • Main openings in partitions (doors)
  • Door swing
  • Room names and numbers
  • Grid references (when applicable)
  • Stairs (in outline)
  • Fixed furniture (including loose furniture where its disposition in a room is predetermined - e.g. desks set out on a modular gird, etc.)
  • Sanitary fittings
  • Cupboards
  • North point

Items which tend to be included, but should not be:

  • Dimensions
  • Annotations
  • Details of construction – e.g. cavity wall construction
  • Hatching and shading
  • Loose furniture where its disposition is not predetermined
  • Section indications


[edit] Elevations

Elevations usually show the outline of the building, opening details and sizes, level datums and floor position. An elevation should give an impression of how one face of the building will look from the outside.

Typical elevations drawing.png

[edit] Estate road layout

Should be at either 1:1250 or 1:500 scales. Line types will fulfil an important role in this type of location drawing. The identity of buried items will be indicated by different line types. Conventions and symbols will indicate hard and soft landscape details and street furniture should be indicated by symbols.

[edit] Assembly drawings

The purpose of assembly drawings is to show how the building is erected on site. Information will include component identification and reference, assembly dimensions and tolerances with reference to component drawings.

The assembly drawings can be:

The assembly drawing number is prefixed by the letter A. Standard details need an efficient library coding system to aid retrieval and sorting, and the Common Arrangement of Work Section (CAWS) reference system found in the standard old Method of Measurement (SMM7 - now replaced by the NMR2 and Uniclass). Some assembly drawings will show:

  • Substructure section
  • External wall details
  • Wall openings such as head, sill and jamb sections, plans
  • Eaves details
  • Internal walls
  • Stair details

The structuring of drawn information into specific sheets helps the search patterns of the end user. Some unenlightened designers will fill the drawing sheet with a mixture of plans, elevations and, if there is room, detailed sections. The titled chosen for the drawing sheet is the first indication of the content of the sheet. Search procedures by the end users follow a pattern and the drawings should be structured and titled to maximise this procedure. Recommended scales fore assembly drawings are: 1:50; 1:20; 1:10.

Typical section drawing.png

The drawings will comprise plan view and sections, and the thickness of lines will depend on the information hierarchy. Outlines and different components drawn with thicker lines alert the user to key information as the eye scans the entire drawing. The placing of the section on the drawing sheet should be carefully laid out to minimise search time for the end user.

Identification of materials using standard conventions will complement the annotation and convey the extent of the materials used in the assembly detail.

The amount of text and dimensions included on the sheet should be just enough to achieve the purpose of the drawing. For example, a drawing of a substructure detail should not include text or specification relating to the roof. When placing text and dimensions onto the sheet, it is best to assist the end user by leaving the drawing area uncluttered. The focal point is the drawn detail. Once the diagram has been assimilated, further information is sought, with the eye radiating out form the focus diagram. The diagram should therefore be encircled with dimensions and text, and the text should be legible, concise and accurate.

Code references direct the user to further drawn information such as component drawings or to the bill of quantities. The specification or the measured section of the bill of quantities should explain the quality of the material or workmanship. This will avoid expensive duplication of specifications on the drawings, reducing the possibility of discrepancies between tender and contract documents.

[edit] Component drawings

This type of drawing shows individual components in the unfixed state. Information will include component sizes, tolerance and specification with reference to the bill of quantity.

The component drawing number is prefixed by the letter C, and typical component details are:

  • Wood window head detail
  • Special door construction
  • Sill
  • Coping stone

Typical construction detail.png

Component drawings are often large-scale, sometime full-sized drawings showing individual components. Assembly drawings will contain several components, showing how the individual components fit together to make a building element.

Recommended scales are:

  • 1 :10
  • 1 : 5
  • 1 : 2
  • 1 : 1

The component drawings will contain dimensions and some text, but the material specification and the minimum acceptable quality will be defined in the specification section of the bill of quantities. The CAWS reference code will direct the end user to the correct part of the bill of quantities.

[edit] Projections

[edit] Orthographic projection

Orthographic projection is a way of illustrating three-dimensional objects in a two-dimensional drawing. The basic drawing layouts are shown below.

First and third angle projection.png

Drawing projections must comply with the relevant British Standard to prevent misunderstanding and avoid errors in interpreting the drawing. The orthographic projection commonly used in Britain is called the first angle projection, but there are other less common projections that can be used to illustrate a three-dimensional object.

[edit] Axonometric projection

The advantage of an axonometric projection is the true plan set at 45 degrees. It is suitable for interior and kitchen layout. Planning drawings are effective as axonometric projection to show the relationship of existing buildings, topography and the proposed building.

[edit] Isometric projection

Unlike the axonometric projection, the isometric plan view is slightly distorted and can be used to show the nature of the design more clearly than an orthographic projection. It is sometimes used during the conceptualisation of the design to help the client grasp the mass of the proposal.

[edit] Oblique projection

When primary information is drawn in elevation, the interpretation can be enhanced by an oblique projection.

[edit] Preliminary drawings

These drawings are often refereed to as thinking drawings, and illustrate elements of the design. The freehand sketches are broad strokes with little detail and illustrate mass, proportion or other aesthetic principles. Soft pencil or a fineliner pen on detail paper is the preferred medium. To avoid deception the detail paper is often grid paper to ensure a correct proportion of images. The focal point of the building can be quickly illustrated by a preliminary sketch. Simplicity and avoidance of detail are the main aspects of a good preliminary drawing.

[edit] Sketch drawings

The entire range of drawings can be illustrated as sketch drawings. A location drawing can be 'key' or control drawing, showing control dimensions or levels. A sketched assembly drawing can be used by the architect to instruct the technician preparing the ink negative. To avoid misinterpretation of size, it is advantageous to use a modular, grid ruled plan, in which the main grid is 300 mm, with a secondary grid of 100 mm.

Typical sketch drawing.png

[edit] Working drawings

These are the final drawn instructions which the builder will use on site to convert the design ideas into a real building, and care must be taken to ensure accuracy of dimensions and specification. In preparing the location plan it is best to use a control box when hand drawing a working drawing – that is, maximum design length and width are drawn on the tracing film. All details should fit within this control box, and if you find you are drawing outside the control box you should stop immediately as this indicates an error in the detailed measurements. Once the drawing has been completed in ink, clean up the drawing and erase the control box.

When a drawing is being produced, thought must be given to the structuring of information. A drawing contains certain information that must be observed. This is primary information, shown by thicker lines and/or high intensity. Secondary information will be shown by lines of medium thickness, while tertiary information will be indicated by thin lines. With ink drawings on film or tracing paper, different pen thickness will achieve the necessary information hierarchy.

[edit] Specification

All drawings require annotation describing the elements or identifying the components. As these descriptive notes and words must be clearly understood, it is essential to aim for legibility if they are hand written, which means taking time to:

  • Form and shape each individual letter.
  • Space letters and words correctly.
  • Arrange the text to help the end user.
  • Arrange the text in hierarchical context.

To help achieve clarity of specification, stencils and dry letter transfers are available. When using CAD, take the time to select a clear and suitable font. Fonts like Comic Sans should never be used on any formal documents, signage, publications or drawings.

[edit] Bill of quantities

The bill of quantities – which is, first, a vital tender document, then a contract document – should be an accurate description and quantification of the project. There should therefore be a cross-reference to the tender drawing and architect's notes or specifications.


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[edit] Related articles on Designing Buildings Wiki

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