University of Virginia Library

I.12.3

LACK OF DEFINITION OF WALL
THICKNESS

The walls of the buildings of the Plan of St. Gall are
rendered as simple lines. This fact has given rise to two
widely held assertions of questionable validity. One of
these, voiced as early as 1848[249] and frequently reiterated, is
that the designing architect failed to give any consideration
to wall thickness. The other, more recently advanced, is
that any preoccupation with wall thickness would have been
intrinsically incompatible with the ideal character of the
Plan.[250] As far as the first of these two contentions is concerned,
attention must be drawn to the fact (generally overlooked
in previous discussions of this point) that there are
two significant exceptions: the bases of the columns in the
nave of the church and the foundations of the arcade piers
in the western paradise are rendered as squares, in their full
planimetrical extension. Second, although the draftsman
drew his walls in simple lines, there is clear indication that
he was fully aware of the complications that might arise in
the actual erection of buildings drawn in linear projection
in such areas of the site where the masonry in two adjacent
structures would congest the available building space, unless
special provisions were made to forestall that eventuality.
The fact that the aisles of the Church are 22½ feet
wide and not 20 feet, as their titles prescribe, finds its
explanation, as will be shown later on, in the draftsman's
awareness of this danger.[251] Yet even here he does not go so
far as to draw the walls with two parallel lines, but guards
himself against cluttering his plan with unnecessary details
by simply moving his wall lines farther outward and thus
introducing a safety margin of 2½ feet on either side of the
Church. His decision to render the walls of the buildings by
single rather than double lines has little to do with the ideal
or paradigmatic nature of his subject, but is clearly conditioned
by the small scale of the Plan. Even today, as Konrad
Hecht has pointed out correctly, an architect faced with the
design of a project of similar complexity, drawn at a comparable
scale, would invariably choose the same method.[252] It was for this very reason that the architects who designed
the monumental marble plan of the city of Rome chose

[ILLUSTRATION]

46.A.B.C. FORMA URBIS ROMAE

ROME, ANTIQUARIUM COMMUNALE DEL CELIO

[after Carettoni, Colini, Cozza, and Gatti, Rome, 1960]

These fragments are of a plan of the city of Rome, etched in marble during the reign of Emperor Septimius Severus, between A.D. 205 and 208.
This plan, incised on numerous marble slabs, was installed near the Forum of Peace, on the wall of a building which before the fire of 192
served as municipal archives. A probable outgrowth of the emperor's fiscal reform, the plan may have served as a monumental compilation and
permanent record of numerous archival and boundary maps. Mounted on a base 4 meters high, the plan itself covered a surface about 42½ feet
(13m) by about 59 feet (18m), an impressive area of ca. 2,500 square feet (234 sq. m). It was drawn at a scale of 1:240, occasionally varying
to 1:245.

The walls of the overwhelming majority of buildings are drawn in single-line projection. A typical example of this method is shown in A, a
marble fragment showing the plan of the Horrea Lolliana and adjacent structures (fragment 25; Carettoni, pl. XXV). Exceptions to the rule are
found in the rendering of the plans of temples, where the cellar walls are indicated by parallel lines, as is shown in fragments 31bb and 37a,
delineating the temples of Argentina and Juno (IBID., pls. XXIX and XXXII, respectively).

single-line definition as their standard mode for rendering
walls.[253] When the Romans were faced with the task of
drawing the plan of an individual building, at a larger scale,
they defined the walls in thickness by two parallel lines, as
was done on the marble slab of Claudia Octavia, now in the
Museum of Perugia (fig. 48), and on a number of other
Roman fragments displaying house plans.[254]

This mode of rendering is of great antiquity and we can
safely assume that it was used at all times in all civilizations.
It existed in Egypt at the side of the more pictorial representations
of the type exemplified by figure 45.A, as is clearly
displayed by the detail of a house plan of the New Kingdom
shown in figure 49. Indeed the most accomplished plans
of this kind, as Ludwig Borchard has pointed out, were
probably those which Egyptian architects chiseled in full
size into the pavement of sacred sites, to be used as guidelines
for the masons who built the walls of the temples that
rose in these places.[255] The designers of the Forma urbis
were not entirely consistent in their use of the single line,
but interspersed it with a small number of buildings where
walls are defined by parallel lines. This was done, it seems
without exception, in the rendering of temples (here
exemplified in figures 46.B-C)[256] and it looks very much as
though this departure from the regular method may have
been motivated by the desire to throw into visual prominence
buildings of a strictly religious nature. The designer
of the Plan of St. Gall could have introduced a similar variation—the
church plans in the Cod. Rhenaug. LXXIII
(figs. 41-44) show clearly enough that the definition of
wall thickness by means of parallel lines is fully within the
range of working patterns of a Carolingian architect. If he
chose to stay away from this type of rendering, he did so
predominantly for stylistic reasons, viz., the desire for
homogeneity of design and, above all, an unwillingness to
clutter up his plan with parallel lines that could be confused
with benches, or run parallel to benches, as they would have
done practically everywhere along the walls of the Church.