Chapter 5
Masonry structures
5.1 Introduction
Masonry has been used for the construction of
buildings from earliest times and the history of
its use comprises buildings in virtually every
architectural style. It is a composite material in
which shaped natural stone or manufactured
bricks or blocks are bedded in mortar. It is
brittle, with moderate compressive strength but
little strength in tension and it therefore
performs well in structural elements in which
axial compression predominates, such as walls,
piers, arches, domes and vaults, but will crack if
subjected to tensile stress resulting from the
application of bending. Where masonry
elements carry bending-type loads they must be
designed such that tensile stress is maintained
at a very low level. If the element is subjected to
pure bending, as in the case of a lintel or archi-
trave, the tensile bending stress has to be
minimised by the adoption of generous dimen-
sions for the cross-section and an acceptance of
very short spans. If the element is subjected to
a combination of bending and axial compres-
sion the arrangement must be such that the
tensile bending stress never exceeds the level of
axial compressive stress. This is done by ensur-
ing that the elements are sufficiently thick.^1
Where the intensity of bending is high, as
can occur in long or high stretches of wall
subjected to wind loading or where high walls
support vaults or domes, the overall thickness
of element required to contain the bending
stress within reasonable limits can be large. In
such cases various measures can be adopted
to achieve high overall thickness without the
need for a large volume of masonry. Often, the
structural devices which make this possible
provide the stimulus for architectural innov-
ation (see Section 5.2).
The forms which are appropriate for masonry
structures are suitable for any material with
similar properties (i.e. materials with moderate
compressive strength but little strength in
tension or bending). Baked earth, mud and
unreinforced concrete are examples of such
materials.5.2 The architecture of masonry -
factors which affect the decision to
use masonry as a structural material
5.2.1 The aesthetics of masonry
The architectural vocabulary of masonry is that
of compression: the structural forms are those
of the loadbearing wall, the buttress, the arch,
the vault and the dome. The two great trad-
itions of Western architecture, the Gothic and
the Classical, were each developed through the
medium of masonry structures and each found
its greatest architectural expression in
masonry. Masonry accounts for some of the
most spectacular of the world's buildings, both
in terms of physical scale and visual qualities.
The architectural use of masonry is here
reviewed under the three headings of vaulted
halls, domes and post-and-beam structures.
Much of the architecture described is pre-
twentieth century but this is necessary so that
the full range of the architectural potential
offered by masonry can be illustrated. 1471 The factors on which the relationship between bending
stress and the dimensions of structural elements
depends are explained in Macdonald, Structure and
Architecture, Chapter 2.