Today’s building production is characterised by an astonishing accumulation of architectural objects that have no stylistic correlation with each other. Each designer tries to distinguish himself from his neighbours; individualistic design and the consequent personalisation of buildings have replaced the concept, which existed until the middle of the last century, of contributing to a global and homogeneous development of construction.
The beauty of the ancient city consisted in the homogeneity of the whole, both in terms of building types, construction materials, colours and finishing elements, which stemmed from a consolidated local tradition that differed greatly according to the geographical and cultural area.
In this context of architecture our tradition has stratified coherently on itself with harmonious evolution over the centuries. It is easy to understand the need to spread the building type and, as a constituent element of the type, to propagate according to common rules the use of building materials available in the area.
In particular, this article deals with the well-founded and important tradition of wooden building structures in the middle Po Valley area.
It is clear that the historic city and the buildings scattered throughout the countryside, both for specialised and basic construction, i.e. housing, used building materials that were mainly available in situ: wood from trees in wooded areas, fired or unbaked bricks in areas rich in clay, river stones in the peripheral river areas, quarry stones in areas rich in boulders, river reeds in areas rich in marshes.
These materials were used according to rules that were the spontaneous heritage of each designer in relation to their own constituent characteristics and bioclimatic features.
Historical wooden structures
In detail, it is possible to argue the atavistic use of wooden structures in the load-bearing and non-load-bearing elements of traditional building in the Po Valley area.
Local materials were preferred to others, even if of higher quality, but coming from distant areas, because the characteristics and methods of use of local materials were better known, and also because problems due to transport by uncomfortable methods were avoided.
The same bricks used for building in the Po Valley area were introduced slowly, especially for dwelling houses, due to the high cost of bricks but, above all, due to the persistence of traditional building techniques acquired from a centuries-old use of readily available plant material. In fact, at the end of the 15th century there was still the use of mixed material for vertical wall structures. The process we are witnessing is that of a progressive substitution of wooden material with brick, which came into use first and foremost and necessarily for fortification structures.
Why was timber construction used in areas especially in Bologna and Modena where there is still much evidence of it, as in the houses with wooden porticoes in Bologna (e.g. Casa Isolani) or in the houses in Cento (e.g. Casa Pannini with frescoes by Guercino)? First of all, we must consider the nature of the land: unstable and marshy terrain where building with vertical piles driven into the ground guaranteed static resistance of the building organism, unlike a continuous and heavy wall structure with linear foundations.
We should not underestimate the presence in the area for many centuries of the Boi Gauls and the Longobards, peoples who influenced the local building culture with their predominantly wooden and light construction tradition.
The historical dynamics of construction in the Po Valley area is as follows: for a long period, from the early Middle Ages onwards, dwellings were made entirely of wood, including the vertical structures, floors, roofs and stairs, while the interior walls were made of arellate, i.e. light walls with marsh reeds, while the roofs were made of straw until almost the end of the 15th century (later banned by the municipalities for obvious reasons of fire resistance).
In the towns and countryside of the central Po Valley, there are still many examples of this age-old building tradition made entirely of wood and vegetation.
The wooden tradition in these areas never disappeared: vertical wooden structures were gradually replaced by baked clay bricks and so were the internal walls, but the exclusive use of wooden floors with beams, joists and roofs with wooden structures and trusses continued until the mid-20th century.
It is interesting to note that it is only in the Po Valley that the custom of making pilaster strips out of brick remains, to stigmatise the wooden genesis of the structural type. A clear example of this process in progress is the eighteenth-century project for houses with stables with separate bodies in the Bolognese countryside by the architect Carlo Francesco Dotti.