The Pantheon: From Antiquity to the Present Page 25

  At the same time, we need to allow for a break between laying the foundations proper and erecting the substructures above them, which could have been as much as several months while the concrete completed curing and gained strength. Although it may be that the proposed three months between the construction seasons would have been sufficient, we need to bear in mind that since the domed rotunda was pushing Roman construction technology to its limits, a longer period may have been considered necessary. Site preparation, for example, could have been carried out in one year and the foundations laid at the beginning of the next season. Some work could have progressed in the meantime, for example, lime slaking, which preferably had to be done at least three months ahead of the time needed,37 andthis period might also have seen the accumulation of materials in on-site depots ready for the major construction phases. Of course, the uncertainties over the details and extent of the foundations just discussed mean that the labor requirements given here are likely to be lower than they were in practice, just as the time period could easily have been longer. This all makes an actual starting date of the main part of the structure before AD 114 highly unlikely.

  Year 2: The Lower Zones of the Rotunda and the Intermediate Block

  The second year of the proposed schedule is probably the most secure, with the rotunda and intermediate block rising together. In this year it is also necessary to take into account the time required for erecting the columns and entablatures of the main interior order at the end of the season. As the entablature blocks over the columns of the recesses were embedded into the concrete walls of the drum on either side and supported in the center on the paired columns, the subsequent sequence of construction meant that they could not have been inserted later. The absolute minimum possible time for this, given that the elements have to be erected in sequence – base, column shaft, capital, architrave, frieze, and cornice – is about five days. If all were erected together this would require 14 teams of at least 11 skilled stoneworkers, each team with its own crane, plus a large number of men to provide the motive power for each (up to 40 in the case of the columns shafts). Given that the columns in each pair are quite closely spaced, however, one team for every pair of columns gives a more likely maximum number of teams, although only three or four would be feasible concurrently. If we leave, say, 15 days at the end of the 270-day season for this process, then there are only 255 days for erecting the masonry of the lower zone, needing just over 190 men (Table 6.5), approximately the same number as suggested for the foundations. The building of the lower zone of the intermediate block adds another 40 men, while 80 stone carvers would have been needed over the same period for preparing the architectural elements, if indeed this was done on site or nearby.38 It is also possible that work had started on these elements during the previous year, and a period of 340 days requiring on average 60 stone carvers is suggested here. Much would have depended on the availability of the large blocks needed, especially the column shafts, and this is therefore one of the more difficult elements for which to estimate the numbers of craftsmen required.

  Years 3–5: Completing the Rotunda and the Grottoni

  As the manpower requirements for the middle zone of the rotunda are very similar to those of the lower zone, requiring 215 men on average if spread over 255 days, in theory this could also have been completed in a year. A short period of 15 days has again been taken out of the 270-day season at the end of this construction phase to raise and put in place the interior cornice blocks, a simpler operation than installing the interior order but similarly requiring the blocks to be embedded in the concrete; using the same equipment this would have needed roughly 50 men. Preparing the blocks for this cornice could have been done by just 7 men over 365 days, or 60 men over 40 days if the team that had worked on the interior orders was used.

  The building of the grottoni, however, adds a level of complexity to the scheduling, which is open to several possible solutions. While the foundations of the grottoni could have been dug and filled in as little as 20 days with 70 men, there is an upper limit of 135 men based on a 3 meter spacing of bricklayers at the face for each of the lower and middle ranges. This gives a minimum construction time of roughly 85 days for each of the two levels. Scheduling for this depends on the point at which the decision to add the grottoni arose. They are independent of the rotunda until about one-third of the way up the middle zone, and so one schedule might see the foundations of the grottoni begun at the start of the season, then being left to gain strength for, say, 80 days, while work continued on the middle zone of the rotunda, and then resume with the lower range of the grottoni, continuing without interruption with the middle range, and finishing after 190 days at the end of the season while the internal cornice was being added to the interior of the rotunda. In this schedule, the building of the grottoni is designed to operate in tandem with that of the rotunda, gradually catching up to end just behind it. This would produce the physical abutting of the grottoni that can be observed in the structure. It would mean, however, that the necessary workforce would have to have been more than half as large again as required for the lower zone of the rotunda, some 330 men.

  If we accept, however, that the grottoni were an attempt to redress a perceived structural weakness in the drum,39 then it is likely that an extra year needs adding to the schedule. In this reconstruction, the fault would have manifested itself early in the third year of construction while the middle zone of the rotunda was being built. Work on the rotunda would have been suspended for at least 190 days, to build the foundations and then the first two levels of the grottoni, requiring only 135 men.

  Work could have recommenced on the middle zone of the rotunda and the final level of the grottoni (the bridge) in the fourth season, requiring 240 men altogether over 160 days, plus 15 days for the interior cornice to be put in place. The scheduling at this stage is further complicated by the fact that manpower requirements increase and speed of construction decreases with height, because of the extra time and effort needed to get materials to their required positions, to erect scaffolding, and for the men themselves to move around the building. While it may appear natural to have waited until the following season to start building the upper zone of the rotunda, it would have been difficult to complete this section in a single season without greatly increasing the workforce. Even allowing for starting within the extra 95 days left at the end of the fourth season of construction, an average of 240 men would have been needed to complete the upper zone of the rotunda and grottoni in the 270 days of the fifth season. This would have given three months for the drum of the rotunda to gain strength before erecting the main part of the dome in the sixth season.

  Years 6–7: The Upper Dome, Intermediate Block, and Portico

  Rather different concerns affect the scheduling in the final stages of the work, in particular the sequence in which the building operations are carried out. One difficulty is that, unlike the walls of the drum where there would have been masons working at both internal and external faces, the upper part of the dome could only be laid from the external face, as there was a solid centering behind the internal face. This means, therefore, that only half the number of masons could have worked on the dome at any time compared with the number who worked on the drum. This problem is compounded by the fact that the length of the workface also decreases as the dome rises, so that while 58 masons could have worked at the outer face at the base of the upper dome, only 9 could have worked at the oculus with the assumed spacing of 3 meters. Work therefore necessarily slows down considerably as the dome enters its final stages, with the result that it is very unlikely to have been completed in a single season of 270 days, and a minimum period of 345 days would be a better estimate; about a third of that period would have been needed just for the final section above the coffers. A schedule that saw the dome built up to the end of the coffering in the sixth season would have required roughly 200 men, with 90 working on the final section in the first 120 days of the next season. />
  Such a schedule has some advantages. The lower two-thirds of the dome is both more vertical and, particularly with its stepped extrados, better able to contain any horizontal elements of thrust. By allowing it to gain strength over the winter, it would have become self-supporting, potentially allowing for the complex formwork and heavy scaffolding required for building the coffers to be removed before the crown was added. The lower dome would then have been much more effective in supporting the crown, constructionally the most difficult part of the operation due to its increasing horizontality, and structurally the part most at risk of failure for just the same reason. The relatively small and lightweight crown in turn could have been decentered toward the end of the seventh season. Removing the formwork for the dome in two stages in this way may have been easier than decentering such a vast span in a single action.

  This still leaves the completion of the intermediate block, and here there are several possible solutions. The upper level could employ no more than 50 masons over a minimum period of 57 days, with an overall workforce of about 100 men. The solution suggested here is to build the middle level of the intermediate block with the lower part of the dome, using 40 men over the whole season. As the completion of the intermediate block is an essential prerequisite for the construction of the portico, the latest it could be completed, assuming the portico was begun in the seventh year, would have been at the same time as the crown of the dome was being built, with its much reduced workforce. Spread over the 120 days needed for finishing the dome, the final section of the intermediate block would have required only about 50 men.

  Considerations of logistics are even more important when we examine the erection of the portico. Here it would be theoretically possible to put the whole of the portico colonnade in place in 9 days, with 230 men divided into 16 teams, raising each column and entablature sequence simultaneously. Given the relatively restricted amount of space available around each column, especially the internal ones, this is unlikely, and there would be additional problems in raising the roof trusses once all of the colonnade was in place. A more logical scheme would be to start erecting the colonnade from the rear against the intermediate block, putting in place first the marble piers and then the inner row of columns, followed by the corresponding entablatures and finally the first and second roof trusses over the piers and the columns. Work would then progress outward toward the facade, so that once the pediment was in place, the main supporting structure of the roof was already complete, and the actual roof timbers and marble tiles could be put in place. Even this would make it awkward to maneuver the larger blocks, especially the column shafts and architraves that needed two cranes, into place, particularly for the inner columns. Here it is assumed that only two columns or entablatures were erected at the same time, starting with the inner pair and moving outward. Similar considerations apply to the blocks of the pediment and its cornice. The columns and entablatures would then take a minimum of about 50 days, allowing for the cranes to be moved, with a further 0.5 day for each truss, and 11 days minimum for the pediment. The roof adds a further minimum of 30 days. If the same crew of 50 men were used throughout, the whole could be done in about 130 days, although more men would be needed at specific times to raise the largest blocks. Before this, all of the stonework (columns, entablatures, and roof tiles) would have needed to be prepared, which could have been done over two years of 340 days by the same 60 workmen who prepared the internal orders.

  Years 8–9: Decorating and Finishing

  The final years of the schedule are required for finishing the detail of the architectural orders and for surface decoration. Calculating these would be another exercise entirely, but finishing the interior order of the rotunda, and the order and main stonework of the portico, require roughly 25,000 mandays each. For the portico, considerations of the logistics of working suggest that it might have needed two years with a team of some 50–60 marble workers, so that if we also take into consideration the construction and finishing of the internal aedicules as well as the surface decoration, a two- to three-year decorative program seems the most likely.

  The relative schedule presented here can be given possible minimum absolute dates. As argued previously, a start date before AD 114 is unlikely, and is consistent with the stamps from the middle and upper zones of the rotunda. If we allow that bricks began to be used very shortly after they were made, the presence of bricks of AD 115 in the middle zone of the rotunda means that it should have been under construction by 116 at the latest, while those of 117 in the grottoni bridge would also work with this schedule. Completion of the decoration would not therefore be possible before 122, and if Lanciani’s report of a fragmentary stamp from behind the decoration of the portico pilasters is correct,40 the finishing and decoration phase may have either continued, or the actual construction been extended, for an extra year or so. The precise dating within these narrow parameters is unrecoverable, and to some extent immaterial for the arguments of this chapter. The key point is that the scheduling suggests the minimum overall time required for completion, and the minimum average number of workers required for that schedule. A longer schedule would only reduce the average number of workers required.

  The Pantheon in Context

  The results presented here represent only one possible schedule, relating only to part, albeit the main part, of the labor needed for the erection of the Pantheon. To these should be added the work necessary to produce and transport the building materials, which may have increased the workforce by about one-fifth if the Baths of Caracalla are any guide, and all of the small elements such as the exterior brick and travertine cornices that had been omitted for simplification, plus such imponderables as the dome centering. Nevertheless, the figures are remarkably modest for a structure that looms so large in the history of Roman architecture. Even for the suggested nine-year schedule, in most years the minimum workforce engaged in actual construction would not have needed to be more than 240 men, a relatively modest figure compared with a minimum of 4,000 men required for building the central block of the Baths of Caracalla, one of the largest construction projects ever undertaken in Rome, with the possible exception of the aqueducts.41 It should be remembered, for comparison, that the Baths of Trajan, completed perhaps only five to six years before the Pantheon was started, would have required a workforce of similar size to that of the Baths of Caracalla. Even if we increase the workforce for the Pantheon by, say, 20 percent to allow for waste and for men working at less than their full capacity, the numbers are still quite small.

  But the Pantheon was not a stand-alone structure (Plate III). In front of it was a porticoed precinct that would have required further manpower for construction, but not necessarily more at any one time, as it must have been built largely after the Pantheon itself was finished, having most likely acted as a works yard for the Pantheon build. The Basilica of Neptune, on the other hand, was constructed at the same time as the Pantheon and physically linked by the grottoni bridge, so that the total numbers of men working at any one time may have been up to a third again as were required for the Pantheon, making a minimum of 300 men in round figures for the two structures. This workforce might then have gone on to work on other buildings in the Campus Martius, particularly the rebuilding of the Saepta and the Baths of Agrippa in the 120s which apparently formed part of the same project of restoration after the fire in AD 110.42 The impact on Rome’s working population could, of course, have been spread wider than this group, as most of the workforce were general laborers and, hence, likely to have been hired only for the short term from a large pool. Nevertheless, the total impact would have been small compared with most of Trajan’s other building projects.

  The Pantheon would have had different connotations for Trajan and for Hadrian as part of a fairly extensive restoration project following a major fire. All of the buildings involved were closely associated with Agrippa and thus with Augustus, so that their restoration befitted the emperor who bore the title o
f optimus and was often spoken of in the same breath as Augustus, following Augustus’s own practice (Res Gestae 20.1) and a long tradition of restoration of public monuments going back into the Republic, with the buildings retaining their original names. Only the completion of the project under Hadrian caused it to be associated with him rather than with Trajan. Hadrian’s own temple building projects, the Temple of Deified Trajan and the Temple of Venus and Roma, arguably would have been far more important for him politically than the Pantheon. The Temple of Deified Trajan, the only one that, according to the sources, Hadrian put his own name on, was a key tool in helping legitimize his succession, and it seems to have used a 60-Roman-foot order, comparable to that of the Temple of Mars Ultor. If we accept Amanda Claridge’s new reconstruction of the temple as hexastyle,43 it would have needed 12 giant gray granite shafts, fewer than the 16 exterior columns of the Pantheon porch, which, as Davies, Hemsoll, and Wilson Jones have argued, were originally designed to be of this size.44 One could therefore suggest that Hadrian, rather than privileging the Pantheon as the epitome of Roman temple construction, commandeered the columns that Trajan had intended for the Pantheon for his own temple to his deified predecessor. The Temple of Venus and Roma made an even greater impact on the topography and political life of the city. The temple was connected with the festival of the Parilia, later known as the Romaia, and is commonly called simply “the temple of the city” in Roman sources.45 Consecrated in AD 121 when the Pantheon was all but complete, and possibly still not finished at the end of Hadrian’s reign, this was the largest temple in Imperial Rome, employing 124 columns 60 Roman feet high, more than ten times the number for the Temple of the Deified Trajan. Moreover, it not only occupied a central position between the Roman Forum and the Flavian Amphitheater but also required the drastic moving of the Colossus of Nero to accommodate it. In plan and height the Temple of Venus and Roma had much in common with the Temple of Olympian Zeus in Athens, which Hadrian is said to have completed, and even features on Rome’s coinage, unlike the Pantheon. Thus, rather than thinking of the Pantheon as Hadrian’s great achievement, we should reserve that accolade for the Temple of Venus and Roma.