283757893275

200 Barry’s Advanced Construction of Buildings
Cold formed steel
top hat section
for booms
slope of 1 in 60
Steel rod welded
to booms
Top hat section top and
bottom booms
Shallow pitch lattice beam
Top hat section top boom
Slope of 1 in 60
End plate
Top hat section
bottom boom
Figure 4.41 Tapered lattice beam.
Steel rod welded to top and
bottom booms
The majority of lattice beams used for flat and low-pitch roofs are fabricated from hollow
round and rectangular steel sections. For most low-pitch roofs to be covered with profiled
sheeting, a slope of 6° is provided, as illustrated in Figure 4.42.
Space grid flat roof construction
Where there is a requirement for a large unobstructed floor area, such as exhibition areas
and sports halls, a space deck roof can be used (Figure 4.43 and Figure 4.44). A two-layer
space deck comprises a grid of standard prefabricated units, each in the form of an inverted
pyramid, as illustrated in Figure 4.45 and Photograph 4.12, Photograph 4.13, Photograph
4.14, Photograph 4.15 and Photograph 4.16. The units are bolted together and connected
with tie bars to form the roof structure. The tie bars can be adjusted to create an upward
camber to the top deck to allow for deflection under load and also to provide a fall to the
roof to encourage rainwater to discharge to gutters and thus avoid ponding. Photograph
4.14 and Photograph 4.15 show fixing nodes that allow different length rods to be inserted.