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Single-Storey Frames, Shells and Lightweight Coverings 169
services such as lighting and heating, and where the activity enclosed by the building needs
to be heated it makes for an uneconomical solution. Trusses are usually spaced between 3
and 5 m apart (for economy in the use of small section purlins and sheeting rails) and are
often limited to spans of approximately 12 m. Larger trusses can be fabricated to provide
large clear spans.
Rooflights are usually used to provide reasonable penetration of daylight to the interior
of the building, as illustrated in Figure 4.5. The thin sheets of profiled steel sheets used to
clad the walls have poor resistance to accidental damage and vandalism. As an alternative
to steel columns and cladding, loadbearing brick walls may be used for single-bay buildings
to provide support for the roof frames. The masonry walls provide better durability to
accidental damage and vandalism. The roof frames are positioned on brick piers, which
provide additional stiffness to the wall and transfer the loads of the roof to the foundations,
as shown in Figure 4.6. As an alternative, a low brick upstand wall may be constructed to
Corrugated sheeting
fixed to purlins on
lattice steel roof
trusses
Continuous roof lights to
mid-third of both slopes
Corrugated
sheeting to gable
end fixed to sheeting
rails on sheeting posts
Corrugated sheeting fixed
to sheeting rails fixed to
columns
Figure 4.5 Single-bay symmetrical pitch lattice steel roof on columns with corrugated
sheeting.
Purlins fixed across
trusses to support
roof covering
Lattice steel roof trusses
bolted to padstones on
piers of side walls
Attached piers to
side walls
Floor
Loadbearing brick side
wall supports roof trusses
Figure 4.6 Single-bay symmetrical pitch lattice steel roof on brick side walls.