Drawing the set
production information and on to ‘as built’ information. As
the project progressed through these stages information
would constantly be added to the drawing files. The
client might also use them for facilities management
(sometimes called asset management) once the building
was handed over.
CAD possesses many advantages over manual drawing,
even for a small practice. A computer takes up far less
space than a drawing board, so you don’t need as large
an office. It can double up for writing specifications,
getting information from manufacturers over the Internet
or from CDs, sending and receiving messages, and
even doing your accounts. You don’t have to keep pens
clean and pencils sharp.
A drawing created on a computer doesn’t need to be
built up sequentially. Mistakes can be corrected easily
without starting afresh, and revisions and repetitions are
easy to make. You can start on a computerised drawing
even if you don’t have all the information to hand to
complete it, because you can come back later, make
corrections and fill in details. At this level CAD has done
for drawings what word processors did for text.
A good CAD package will also let you automate difficult
or repetitive tasks, so that whole sections of drawings
can be completed with just a couple of clicks on a button.
It should either have all the necessary ‘hooks’ to allow
links with third-party applications when you decide to add
them, or have a file format compatible with architectural
design packages, to make it easier to upgrade later.
Some ancillary equipment is useful. A CD or better still a
DVD writer enables back up copies to be made of
valuable data and copies sent through the post. An A4
flat bed scanner enables site location plans or
manufacturers’ trade literature to be scanned into CAD
drawings. A 4 megapixel digital camera can provide a
photographic record of existing buildings and
topography, saving a return trip to site.
Most offices now use large format inkjet plotters capable
of printing A1 or A0 drawings. Smaller offices might
send small drawings and check plots to the same A4
laser printer as is used for general correspondence and
send larger drawing files direct to plotting agencies over
the Internet.With regard to the actual creation of the drawing files,
two methods are currently in use, the first being both the
most common and the less sophisticated.Drawing overlay method
The basic concept is simple. Each element of the design
is drawn on its own unique ‘layer’ within the computer
file, walls on one layer, dimensions on a second,
electrics on a third, radiators on a fourth, and so on.
Layers can be turned on or off as needed. During the
design process both electric and radiator layouts might
be turned on, enabling electric sockets behind radiators
to be spotted.The concept of layering is common to all CAD programs.
Different programs might use different terminology but
the underlying principle is the same. All programs will
have tools to help you manipulate your layers, by way of
wild carding or through grouping layers. Likewise, layer
names might be preassigned by a high-end fully
automated architectural CAD program, whereas you
may have to devise your own layer naming conventions
with a simpler program. (See Chapter 5 for section on
Layer Naming Conventions.)However, if in doubt, use more layers than fewer. It is
much easier to combine layers to simplify the drawing
file’s structure than it is to separate drawn entities into
two or more layers later.Model exchange method
When drawings are produced by CAD it is probable that
during the design process several different designers will