Civil Engineering Reference
In-Depth Information
partitions to be installed after the roof is constructed. The roof should therefore be con-
structed wherever possible as an independent clear spanning structure between the two
wall plates of the external walls. To avoid trusses inadvertently bearing on internal non-
load bearing partitions, it is good practice to have the roof tiled and therefore under nor-
mal working load conditions to allow any deflection in the truss to take place before the
partitions are fitted.
The trusses are not designed to carry water storage tank loads and thus, wherever possible,
these should be directly supported from partitions below. If this is not practical then the
advice of TRADA or the truss designer must be sought in order that the truss spacing may
be reduced to carry the additional load. One final point on the standard roof assembly is
that some difficulty may be experienced in nailing the ceiling joist tightly to its binder. A
more effective connection is to use one of the readily available light galvanised metal
cleats. These give a much more positive and stronger connection than traditional skew
nailing. Figure 4.4 illustrates the roof construction described above.
Bolted Truss Hips
Hips can be formed using bolt and connector trussed structures, the hip usually being sup-
ported on a 'half' truss, itself supported on one of the principals at hip peak and on the end
wall plate at the hip eaves. A typical hip construction is illustrated in Fig. 4.5. The re-
mainder of the hip timber members follow basically traditional construction techniques,
described in Chapter 3. The hip rafter, however, generally carries the ends of the purlins
and also supports the hanger, which in turn helps to span the binder from first principal to
the end wall plate. It is essential that the ceiling tie member of the half truss used in the
hip end is connected properly into the binder running on the centre line of the roof to en-
sure an adequate tie from one end of the roof to the other.
Valleys
