Figure 2-1.Construction drawing lines.
Main object line: a heavy, unbroken line used to
show visible outlines or edges that would be seen by
people looking at the article, house, or building. The
main object line is one of the most important lines
because it outlines the main wall lines on plans and
sections. It shows clearly the important parts of the
construction and emphasizes the outline of the
Dimension line: a light line drawing outside the
structure or detail to show the distance between two
points. This line is drawn between extension lines with
an arrowhead on each end. Between the arrowheads,
the distance will be given either at a break in the line or
just above the line. On some drawings the scale and the
distance between the two points may not agree; in such
cases, the distance will be given in a dimension line.
Extension line: a line that touches and is used with
dimension lines. This line extends out from the edge or
the point at which the dimension is to be determined.
Equipment line: a light, continuous, unbroken
line used to show the location of equipment, such as
transformers, panels. and galley equipment. This line
is used to allow the electrician to install the necessary
conduit in the proper location during rough-in work.
Symbol section line: lines that are generally solid,
although, for certain conventions, dotted lines of the
same weight may be used. Section lines, evenly
spaced, are used to shade surfaces shown on a drawing
and by these means indicate the material used. Material
section lines are standardized to a certain degree, but
you will find some variations. A set of working
drawings using these symbols would have a symbol
schedule key showing the various materials in that
particular set. This schedule is usually placed near the
title box on the plan of the first floor.
Broken line: a line with wavy breaks in it, at
intervals, used to indicate those parts that have been
left out or that the full length of some part has not been
drawn. The broken line is used in detail drawings
where only a section of the object is to be shown.
Invisible line: a line that is made up of a series of
short dashes. It is used to indicate a hidden or an
invisible edge or edges that are hidden under some
other part of the structure.
Center line: a line that is made up of alternating
long and short dashes and is used to indicate the center
of an object.
Section line: a solid line that has arrowheads at
each end that point in the direction in which the section
is to be taken. This line tells just where the section line
has been cut through the wall or building. The sections
are indicated, in most cases, by the letters A-A, B-B,
and so forth, although numbers are sometimes used.
Do not overlook these section lines on a plan. To obtain
a clear picture of the construction at the particular point
indicated, always refer to the section detail called for
by the letter or number.
Stair indicator line: a solid line with an
arrowhead indicating the direction of the run. For
example, Up 12-R means that there are 12 risers from
floor to floor and that the stairs go up. A riser is the
vertical part of the step; the flat part on which one steps
is the tread. In most cases, the floor plan indicates only
the run of stairs half the distance between floors. For
example, the ground floor indicates a broken line that
tells you the steps continue up. The next floor plan
shows the stair indicator line half the distance to the
first floor, down.
Break line: a thin solid ruled line with freehand
zigzags used to reduce the size of a drawing required to
delineate an object and reduce detail.
ABBREVIATIONS AND SYMBOLS
Blueprints show a small-scale drawing of a full-
size building. Since the blueprints are small in relation
to the actual building, some kind of shorthand is
needed to give the necessary building information.
Abbreviations and symbols are used to show a large
amount of information in a small space.
While there is some standardization of symbols
and abbreviations, a lot of variation still exists. A key
or legend is put on the blueprint to explain their uses.