Civil Engineering Reference
In-Depth Information
Having highlighted the need for both floor joist and purlin support, on a simple attic, con-
sideration must now be given to the solution of the more complicated attic roof as illus-
trated in Fig. 3.12.
It can be assumed that the floor joists will generally be supported either by beams or by
load bearing walls below. In some instances these joists may be doubled to form a beam,
or a separate beam is inserted within the floor which will itself be strong enough not only
to carry the floor but also to support the purlin above. This however generally applies only
to the lower purlin, i.e. the one at the attic wall to the sloping ceiling
