A question of scale

Before beginning a survey with the view to creating a survey drawing you will need to decide what the key elements of a structure are and how best to depict them; the level of detail you can show will depend on the scale of the drawing.

Drawing Scales

Before undertaking a survey with the aim of creating a drawing you will need to make informed decisions on what the key elements of a structure are and how best to depict them; the level of detail will vary according to scale.

A scale ruler is designed to allow you to work out the actual dimensions of a distance on a scaled drawing. Maps, architectural and archaeological drawings are scaled to allow for large areas, structures or items to conveniently fit on a reasonable size of paper. Be careful when selecting the scale on the ruler, as there are normally two scales provided on each edge.

Big or small?

Confusion is often caused by the terms ‘large scale’ and ‘small scale’ in measured survey. In simple terms, as the number gets smaller, the scale ratio gets larger – ratio 1:10,000 (or one to ten thousand) means that the sizes of objects on the map are 1/10,000 of their size on the ground whereas the ratio 1:100 (one to one hundred) means that the size of objects on the map is 1/100 of their size on the ground. Because 1/100 is a larger fraction than 1/10,000, 1:100 is the larger-scale map (in the same way that a half a slice of cake is larger than a quarter of a slice of cake).

The example above shows a plastic spoon life-sized (1:1 larger scale) and reduced by a factor of 10 (1:10 smaller scale). It is not appropriate to attempt to show the detail of the spoon at the smaller scale. If an object is depicted at scale 2:1 it would be twice the actual size. Small elements of architectural detail are sometimes best shown at scales larger than life-size.

What scale should I use?

Before putting pencil to paper you should decide exactly what it is you want to depict – the size and form of a building and its significant structural components. Too small a scale will make it impossible to depict important architectural detail. Too large a scale is likely to take too much time and effort, with little, if any, useful gain in information. It is better to show a building in its entirety at a small scale and enlarge specific areas as separate drawings if you want to show more complex detail.

An example of a small, ruinous single storey building shown drawn at different scales.

Scale has a direct bearing on the way in which particular drawing conventions are applied and the level of detail that can be shown.

Details or features

If you want to show how certain pieces of the building were constructed, you might make a detail drawing of that part; scales of 1:20, 1:10, 1:5 up to life size can be used to illustrate particular features of a building or details on objects of interest, such as carved stones, moulding profiles and small areas of architectural form, as required.

Understanding the process of generalisation, that is, using fewer lines and different line thicknesses to represent a structure at varying scales, is also crucial to the success of the depiction. The smaller the scale, the more generalisation takes place but overall shape and form must not be lost.

The bigger an object or area really is, the smaller the scale of the drawing has to be to enable it to fit onto your drawing board. You might choose to draw a single house at a scale of 1:50 (1 drawing unit = 50 units on the real building). But if you want to draw a plan showing all of the houses on an estate, you might need to choose a smaller scale of 1:200. Similarly to plan an entire neighbourhood would require an even smaller scale, such as 1:1,000.

Another important consideration is fitting the drawing onto your drawing sheet or page! If too large a scale is used, the resulting survey may need to be spread over more than one sheet and this can be both inconvenient and unwieldy.

The logical approach is to create a suite of illustrations at different scales. A range of survey scales is recommended for the various options outlined below.

Site plans

A scale of 1:200 to 1:1,000 is used for a site plan to show the relationship of a group of buildings. A scale in this range allows the illustrator to represent some of the character of the structures, together with their relative positions, and structural elements such as blockings and straight joints.

(Above) Panmure House, Canongate, Edinburgh. This series of simple floor plans shows the layout of a 17th century two storey town house with basement. There is sufficient information to indicate wall thicknesses and openings, but architectural detail and phasing are lacking.

(Left) Pencil drawing of architectural detail drawing held in the National Collection. A section of wall-head cornice showing segmental timber construction detail (for new roof of 1854 possibly). 

Cat. No. DP158246

Publication

In fields outside art, technical survey drawings, or plans of buildings or machinery and other things, are often called ’drawings’ even when they have been transferred to another medium by printing. 

Survey drawings (or derivatives from them) are often undertaken with a view to incorporating them into a publication or report. Frequently these will be A4 or smaller in size, so consideration has to be given to the size of the original drawings otherwise reduction will affect both the printed quality and the ability of the drawing to do its job properly.  

Working to a reduction ratio of 50% or 25% (or half linear and quarter linear as it is sometimes called) provides reasonable flexibility without sacrificing clarity.