The left-hand drawing (9) illustrates traditional loadbearing
wall construction. It is a made-up example. It is composed
of relatively small elements that have to be put together
in particular ways. The walls are built of stone or brick with
joints of mortar which evens out their irregularities and helps
them to be stable. These heavy walls have to be supported on
foundations (footings) that spread the load into the ground.
They also, generally speaking, have to be built vertically so that
the loads transmit directly down into the foundations. Windows
and doorways into such walls have to be small because
the walls above such openings have to be supported by lintels
or arches. Upper floors and roofs are generally composed of
layers of lengths of timber: joists supporting floorboards;
trusses, purlins, rafters, battens supporting roof slates or tiles.
Many buildings still are constructed using similar traditional
materials and construction.
A reinforced concrete structure (10) is fundamentally
different in that it is composed of a liquid material poured
into a pre-built mould – the form-work. Its strength comes
from steel reinforcement rods laid in the form-work before
the concrete is poured. Floors and roofs do not need walls
to support them; columns are sufficient. Floors and roofs, as