ROMAN URBAN TOPOGRAPHY in Britain and the western Empire

Fig 21 Ashlar construction in Sarno stone at Pompeii
(Photo: author)
and concise way of presenting the architect’s instructions
to the builder than was the written word.
A related practice was the use of drawings actually
incised on pavements beside or inside buildings. These
enabled the architect to work out structural or decorative
problems at full scale, and at the same time could act as
templates for the masons. More and more examples have
come to light in recent years. At Pergamum the outline of a
column was found inscribed on the theatre terrace; at
Ling: The mechanics of the building trade
Capua an elevation of an archway was used to guide
masons working on the amphitheatre (Fig 20); and in
Rome more complicated drawings have recently been
identified outside the mausoleum of Augustus. The same
practice continued in the medieval period. It is found,’ for
example, in Wells Cathedral, and a recent survey by Bryan
Ward-Perkins and Sheila Gibson in the cathedral at Trogir
(Jugoslavia) has resulted in a full analysis of 15th- or
16th-century trial drawings in the pavement above the
aisles.
Such full-scale drawings were used mainly in connection
with masonry construction. For concrete it would
have been more useful to have drawings on a reduced
scale. Indeed, the need for such advance planning was
much greater in concrete construction, which was less
bound by convention and thus more susceptible of
innovative design. More important, unlike masonry,
concrete did not rely upon a continuing process of skilled
craftwork and fine adjustment during construction; the
skill was mostly focused on the preparatory stages (for
example, determining the general layout and dimensions,
fixing the form and span of vaults, and building the
centering), while the actual building process employed
unskilled or only partially skilled work-forces - bricklayers,
concrete-mixers, shovellers, and the like.
Construction processes
To look at the processes of construction we must consider
Fig 22 Limestone colonnade in the Forum at Pompeii. Note the ‘flat-arch’ principle of construction in the architrave (Photo:
author)
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