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18 Febbraio 2013


Square ashlar walls in Italy*

Versione italiana

Stone quarry at Cursi (Lecce, Italy)

Having underlined the recent renewal of interest in the use of regular stone ashlars among contemporary architects throughout the world, we thought it would be interesting to track down and present a series of works that could provide practical examples of the permanence of this very same interest in Italy.
Moving beyond the nation’s great urban conurbations and major cities, we have focused on information from certain specific local areas, and in particular those disposing of large quantities of soft stone; the idea behind this was not to try and endorse or encourage local architectural trends, but to see whether the contemporary architecture in these areas possessed a degree of continuity with deep-rooted tradition. Central-southern Italy in particular, with its building stone and varieties of tufa (that soft stone to be found in large seams, which can be easily cut and dressed as soon as it has been quarried), together with other, more circumscribed zones, have provided those particular areas of the country within which we can ascertain the continued use of opus quadratum.
Ashlars for building walls (which in the various local areas are known as either toccoli, tufelli, petrelle, bolognini or cunei) are generally of a parallelepiped shape and of a set size: the length of the ashlar is usually greater than the width, in order to provide a regular, extended supporting base. To this day, square saw-cut blocks of tufa are still sold in a number of Italian regions (Umbria, Lazio, Campania, Apulia and Sicily). The consistency and workability of this particular soft stone has meant that quarries continue to produce levelled, regular blocks of it, thus enabling it to be easily and quickly laid. As far as the dimensions of these ashlars is concerned, over the centuries there has been a gradual move away from the use of massive blocks towards that of more manageable-sized ashlars.
The shapes utilised vary from one region to another, and sometimes from one part of a given region to another. In central Italy, a commonly found form is the flattened stone (quarrel) measuring 30x40x13 cm. (or, on rare occasions, 40x40x13 cm.), which can be used to build walls 30 or 40 cm. thick. Moreover, in such cases, the size of the shorter size (13 cm.) facilitates its combination with bricks to make walls featuring listels. In Apulia, and in the Salento area in particular, forms of Lecce stone or tufa of other sizes are also used.

The building site at Taviano Cemetery

In general, the flat, accurately dressed surfaces of square ashlars, enable the stones to be laid on top of each other and side by side in a highly effective, precise manner.
From our travels around the country, we noted that the appearance of modern stone walls varies significantly, depending on a series of factors, the most important of which are: the specific type of stone utilised and the way the faces of the ashlars are dressed; the wall design (based on the dimensional ratio of the individual elements and the geometrical bonding arrangement); the way the joints are mortared.
In modern times, mortar joints have been introduced to further guarantee the stable bonding of the various stone ashlars, and to ensure the even distribution of load across the entire load-bearing section of the wall. Thanks to the use of mortar, there is no longer any need to dress the ashlars in the precise way ancient masons did, thus making the working of stone ashlars a more economical process than it had been in the past.1
Before seeing the architectural works themselves, it was interesting to visit the sites where the stone was quarried and worked, and we have gathered a quantity of information from the quarry workers and stone masons themselves, which has in turn enabled us to reconstruct the life-cycle of the stone from the quarry to the finished building, from its natural state to the man-made item.
In doing so, we have examined semi-finished products and workshop prototypes, where we were able to see more elaborate, more sophisticated traces of stone work; the surviving signs of the ancient stone-masonry tradition that we thought could in some way provide input not only to the work of restoration, but also to new architectural projects. During the same period in which we conducted our investigation, Renzo Piano’s workshop was being built for the construction of the new Liturgical Hall of Padre Pio at San Giovanni in Rotondo, which with its grandiose dressed ashlars, served as a real-life model for the beginning of a new season of stone architecture.
Passing from quarries to workshops, from building sites to architectures, has led us to discover objects manufactured in stone and “proudly” erected in defiance of the standardisation of industrial manufacturing practice. The stone architectures that have marked the various stages of our journey, despite often leading to meaningful encounters, have continually underlined the importance of the context to the worth of any manufactured item: the latter is never the sole protagonist, a symbol of mere individualism; the familiar features of the materials, the techniques and the figures are always part and parcel of a shared, deep-rooted tradition.

Baldi House (1959-61) in Rome, designed by Paolo Portoghesi

We have tried to gather together a series of architectural works (often isolated in an inexplicable manner) which are of prime importance if we are to sustain a more generalised hypothesis of the rehabilitation of stone architecture, as we need to render it more visible, more capable of being judged, and of greater use to new generations of architects. The number of architectures we have decided to present to the reader is limited, and they do not represent models or prototypes within the local context; on the other hand, they do express a certain value as proof of what certain materials can still offer when combined with a more easily understandable and firmly-established approach to architecture.
These works, together with all the others we have presented so far in the present chapter, help us in the end to break with that negative, deterministic vision of contemporary technical culture with regard to materials and constructive approaches closely linked to architectural traditions of the past.
If our present work only managed to offer a unique point of view, a scenario of materials that differed from the indistinct landscape of global society, we would already be extremely satisfied. In other words, we are keen to show that the comparison, rather than aiming at the pursuit of innovation, tends towards the building of bridges with the traditional architecture that had survived up until very recently.
In rejecting the standardised view of contemporary architectural production, we would like to advance an alternative hypothesis – to be shared, if still possible, with others – starting with a re-evaluation of the constructive teachings, resources and materials that continue to characterise the Italian landscape. In doing so, we find ourselves, in a certain sense, in the position of the person who decides to go back and study a language that he spoke for many years and then suddenly, for no good reason, stopped speaking.
We believe that the plastic approach to wall construction could lead, once again, to the pursuit – in various regions of Italy – of the study, updating, implementation and valorisation of local resources. Everyone is aware of the wealth of natural stone available in Italy, from the northern Alps all the way down the Apennines to the islands of Sicily and Sardinia.
We would like to submit a theory – one that may seem bold but in reality is not – designed to re-evaluate the importance of thick ashlar walls.
Historically speaking, the considerable cost of quarrying and transporting stone has always been accompanied by the cost of transforming it. For this reason, in those areas rich in soft stone that is easy to cut, the traditional use of square ashlars and modelled pieces has survived to this day. You only have to think of the “current” stone materials employed in central-southern Italy which, as well as being economical, are also hard-wearing, compact and attractive. Such is the case, for example, of many softer stones, such as tufa; indeed, it is their very consistency and the ease with which they can be worked which sees quarries producing regular, levelled ashlars of a certain size, ready and easy to use.

The new parish complex (1994-99) at Nepi, designed by Romano Adolini

This rehabilitation of the opus quadratum is particularly evident in those areas of the country where soft stone abounds (despite the fact that the increased technical capacities of modern-day machinery mean that even the hardest of stones is no longer difficult to cut).
Given the greater potential of modern means of transforming stone, architectural use can now also be made of the various types of travertine and of the harder stones widely available throughout the country. With the exception of very few cases, each Italian region still possesses a significant
quantity of building stone, which in theory – given modern stone quarrying and working methods – could be valorised as it was in the past.
The present work will have achieved its aim if it can manage to get future generations interested in this question of stone, which for many years was neglected and forgotten by the technical and architectural sectors, as well as by university research departments.

Alfonso Acocella

* The re-edited essay has been taken out from the volume by Alfonso Acocella, Stone architecture. Ancient and modern constructive skills, Milano, Skira-Lucense, 2006, pp. 624.
1 The pointing of the joints generally takes place after about 2 cm. of the original mortar used to bond the stones together has been scraped out. At this point, the joints are pointed “flush” with the surface of the stone using a fine mortar: this special mortar may include natural earth (or dust) created by the crushing of the same stone used to build the wall, thus giving a mortar of a similar colour to that of the ashlars.
Jointing is performed using special tools (trowels) enabling the mortar to be compressed inside the gaps between the stones, and smoothing it out in a suitable manner, especially when the gaps are wide. Clearly the final appearance of the joints may be emphasised to a greater or lesser degree, depending on the technique used: thus the joints may appear channelled, concave, undercut, sliced (the latter for is achieved using a mortar cord), flat or convex. Furthermore, the joints may be further emphasised by scraping the fresh mortar with a pointed iron guided by a long wooden straightedge.

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