Figure 2-4.A truss rafter.
The engineer works with the architect to decide
what materials to use in the structure and the
construction methods to follow. The engineer
determines the loads that supporting members will
carry and the strength qualities the members must
have to bear the loads. The engineer also designs the
mechanical systems of the structure, such as the
lighting, heating, and plumbing systems. The end
result is the architectural and engineering design
These sketches guide draftsmen in
preparing the construction drawings.
Generally, construction or working drawings
furnish enough information for the Builder to
complete an entire project and incorporate all three
main groups of drawings-architectural, electrical,
and mechanical. In drawings for simple structures,
this grouping may be hard to discern because the
same single drawing may contain both the electrical
and mechanical layouts.
In complicated structures,
however, a combination of layouts is not possible
because of overcrowding. In this case, the floor plan
may be traced over and over for drawings for the
electrical and mechanical layouts.
All or any one of the three types of drawings gives
you enough information to complete a project. The
specific one to use depends on the nature of
construction involved. The construction drawing
furnishes enough information for the particular
tradesman to complete a project, whether architectu-
ral, electrical, or mechanical. Normally, construction
drawings include the detail drawings, assembly
drawings, bill of materials, and the specifications.
A detail drawing shows a particular item on a
larger scale than that of the general drawing in which
the item appears. Or, it may show an item too small to
appear at all on a general drawing.
An assembly drawing is either an exterior or
sectional view of an object showing the details in the
proper relationship to one another. Assembly
drawings are usually drawn to a smaller scale from
the dimensions of the detail drawings. This provides
a check on the accuracy of the design drawings and
often discloses errors.
Construction drawings consist mostly of right-
angle and perpendicular views prepared by draftsmen
Figure 2-5.The most commonly used roof trusses.