Civil Engineering Reference
In-Depth Information
Design Information.
It can be seen that, when requesting a quotation and particularly when ordering the trusses, it is
essential to inform the trussed rafter manufacturer of not only the truss shape and size and num-
ber required, but also the roof tile type and ceiling specification. The best way to ensure that the
design is adequate for the roof under consideration is to send a full set of drawings for the
building project such that this, or an additional specification, includes the information set out
below.
Information required
Reason for data requirement
(1) Dimension between walls To obtain accurate span over wall plates
(2) Size of wall plate
To obtain accurate span over wall plates
(3) Location of wall plates or
other supports
for the truss
To obtain accurate span over wall plates
(4) The overall thickness of
the cavity wall
To determine the top chord overhang required
(5) Width of soffit required
To determine the top chord overhang required
(6) Pitch in degrees, left hand
side of roof
slope
To establish the geometry of the roof truss
(7) Pitch on right hand side of
roof slope
To establish the geometry of the roof truss
(8) Any minimum top chord
size requirement,
particularly if these are to
match existing
construction.
Structural design may produce a rafter of smaller section if no
limit placed upon the designer
