WORKING DRAWINGS HANDBOOK, Fourth Edition

Working Drawings Handbook

parts of a drawing may be grouped within them as
follows:

used in the office will conform to its requirements. It

originates in the ingenious concept of a rectangle having

an area of 1 m^2 , the length of whose sides are in the

proportion 1:√2 (4.4).

The dimensions of this rectangle will be found to be

1189 841 mm and by progressively halving the larger

dimension each time, a reducing series of rectangles is

produced, in which the proportions of the original

rectangle remain unchanged, and in which the area of

each rectangle is half that of its predecessor in the

series (4.5).

The range of ‘A’ sizes available to the drawing office is

as follows:

(a) grid lines

centre lines

dimension lines

leader lines

incidental furniture, where relevant

hatching

(b) all other lines, with the exception of:

(c) those lines, particularly on an elementalised drawing,

which it is desired to emphasise, either because they

define the element which is the subject of the

drawing, or in the general interest of clarity.

The values to be set against the three categories will
vary with the scale and nature of the drawing and with
the range of pen sizes selected.

Recommended pen sizes are as follows:

1 Drawings to a (a) (b) (c)

scale of 1:50

and less

2 Drawings to a (a) (b) (c)

scale of 1:20

to 1:5

3 Drawings to a (a) (b) (c)

scale larger

than 1:5

Pen size Range 1 0.2 0.3 0.4 0.5 0.7

Pen size Range 2 0.18 0.25 0.35 0.5 0.7

Figures 4.2and 4.3, taken from parts of drawings of
various scales, have been redrawn using both pen size
ranges for comparison.

Drawing sheet size

The international ‘A’ series of paper sizes is now
universally accepted, and all drawing and printed sheets

A0: 1189 841 mm

A1: 841 594 mm

A2: 594 520 mm

A3: 420 297 mm

A4: 297 210 mm

CAD uses these paper sizes, with the addition on larger

drawings of a gripping margin for the printer or plotter.

The large differential between A0 and A1 has led to the

introduction in some offices of a bastard-sized sheet to

reduce the gap, but the use of intermediate sizes is not

desirable. They have to be cut from paper of a larger

size, and their non-standard proportions lead to

difficulties in both storage and photographic

reproduction.

Indeed, both these and the A0 sheet should be avoided

wherever possible. The A0 sheet is incredibly

cumbersome both in the drawing office and on site, and

on the whole it would seem to be preferable to set the

A1 sheet as an upper limit in all but the most

exceptional circumstances. The site plan for even the

largest of projects can always be illustrated at the