With the ancient Latin term pérgula, perhaps derived from pérgere “to go ahead, to continue”, originally indicated the palaces or pylons, on which the peasants exposed the fruits to the sun, and also the pews on which merchants exposed their goods.
In later times, with the evolution of the building and acquired the ability to build multi-story houses, the word pérgula was indicated on the upper floor of the building, often overlooking the shop, where the merchant lived.
Still later it was called the highest part of the house, usually consisting of a sort of terrace covered with beams of wood or iron, which had the task of supporting climbing plants, whose presence was used to give shade and freshness, essential in the warm and sunny southern climate.
The pergola has, in fact, remained one of the most typical and decorative elements of the Latin architecture (as is the patio for the Spanish one); from the elegant examples of the Roman villas of Pompeii it has been handed down, through the centuries, in the medieval verzieri (as famous painters, such as Fra Angelico, Mantegna and others have handed down in their pictorial depictions) and in the refined and sumptuous gardens of 1700 , up to the most schematic and rustic forms of our days. The pergola, in fact, appears, in all its possible variations, as an almost essential element of many gardens or terraces, where it frequently takes on the function of living outdoors, creating a harmonious continuity between the closed environment without having to give shade and coolness, essential in the warm and sunny southern climate.
The Pergola has remained in fact as one of the most typical and decorative elements of Latin architecture (as is the patio for the Spanish one); from the elegant examples of the Roman villas of Pompeii it has been handed down, through the centuries, in the medieval vizier (as famous painters, such as Fra Angelico, Mantegna and others have handed down in their pictorial depictions) and in the refined and sumptuous gardens of 1700 , up to the most schematic and rustic forms of our days. The pergola appears.
In fact, in all its possible variations, as an almost essential element of many gardens or terraces, where it frequently takes on the function of living outdoors, creating a harmonious continuity between the closed environment of pillars or columns that look on the free space; in this form, the elements that make up the roof can be both horizontal and inclined, relative to the style of the garden. In the most common meaning, the term Pergola defines a kind of tunnel consisting of two parallel rows of pillars, made of wood, brick, concrete or iron, opposite to each other and connected at the top by horizontal elements; the whole is a scaffolding that acts as a support for every type of climbing plant, both ornamental (floriferous or foliage, to create shady corners), and fruit. And this, in fact, is a typical and characteristic way of cultivating the vine in the rustic gardens of the Mediterranean countries and of the European Mezzogiorno; it is possible to taste good and fresh table grapes and to use the shade of the vine leaves to repair the garden street-beds. On the contrary, in some Italian regions, the pergola is a characteristic system of planting the vineyards, even if it is in disuse due to technical and mechanization reasons; the terms of pergola and pergola are used interchangeably, even if, strictly speaking, the pergola is to mean a very long and large Pergola or a pergola set. The materials with which to create a Pergola are various; very common are the Pergola made of wood or with frames of iron, more rustic instead those obtained with pile-streaks of cement or brick, used especially if the environment is rural and old style; the least exploited material to date is marble, but it has had the greatest use in the past and has remained in the most classic examples, found in many patrician villas, as in the Doria palace in Genoa. Whatever the material with which a P is intended to be made, even before construction, great care must be taken in designing a whole that harmonizes with the masonry of the house, which is proportionate to the size of the garden and has a certain strength. the pergola, in fact, once covered by a thick curtain of branches and leaves, offers a strong resistance to winds, with the consequences that can easily be imagined. If the choice of the building material is fundamentally important, the actual dimensions of the pergola are equally fundamental; in designing this fact we must take into account many factors and, among many, also the type of plants that will grow on the pylons, because, if these are particularly thin and rather vigorous and thick plants, the stability of the construction may be compromised. ; or, if the plants are slender and delicate and the roofs somewhat strong, these are not sufficiently covered by foliage and the whole loses some of its charms. Generally it is considered a minimum height of two meters to allow the transit of people; the width depends on the path or path that you want to cover, but it must not hinder the ease of the passage; on the contrary, a minimum width of 1.20 m should be considered, in order to allow walking at least two people side by side. Among the easiest to realize are the wooden structures; the best construction timbers, available on the market, are oak and chestnut, both very resistant to rotting and to attacks by parasitic insects; naturally, other more current wood can also be used, but these are not as resistant, and therefore there is the need to treat them with suitable wood preservatives, especially in the parts that are buried. The main supports of the pergola must offer the maximum guarantee of resistance and durability; it must be checked that they are healthy, they do not show too many nodules or cracks. The dimensions of the section, mostly square, vary from 8 to 15 cm, depending on the size established for the item; when calculating the length, it must not be forgotten that the poles will be placed in the ground for at least 40-60 cm. The vertical uprights must not be more than 2-2.5 m apart so that the structure is adequately robust; for the same reason the connections between one and the other must be fixed firmly and with particular accuracy. An always advisable method is to keep these poles in place, sinking them into a concrete cast; with this (expediency the stability of the whole construction is never bought even if the plants that grow there develop excessively.
A vaulted flat vault is much easier to make than those with a barrel vault; we use smaller beams than the vertical, at most 8 x 8 cm, to connect these last to each other, fixing them with screws and nails; the most expert in carpentry can make joints that increase safety. If desired, or it is considered appropriate for the aesthetics, these vaulting beams can protrude beyond thirty centimeters. If instead, you prefer to make a barrel vault, you can find on the market, or have a craftsman prepare, metal arches with galvanized iron pipes or rods that will then be firmly fixed to the vertical support posts; but although they may be robust, it can be verified that, once abundantly covered by climbers, under the action of strong winds, they have oscillating movements; for this reason it is preferable to prepare the entire metal arch, even if this, although deeply rooted in the ground, will certainly be lighter than the previous one; it is almost always recommended to increase its resistance by welding horizontal crossbars on it, both sideways and on the vault. This type of pergola has the advantage of being practically invisible, once the plants have completely developed on it and are, therefore, the most suitable to give relevance to particularly interesting plants. Once the supporting structures have been created, any decorative elements may be placed in position, but in most cases, it is preferable not to weigh down the whole with superfluous details and to give maximum emphasis to the vegetation, which, if opportunely chosen, will be the best decoration of the garden. Almost all the gardens are bordered on the boundary by walls of the fence and are accessed inside them through the entrance gate, supported by pillars often completed by an arch or a small rustic roof on which it can grow, with remarkable decorative effect, a beautiful flowering creeper, like roses, rincospermo or bignonia. An arch, of both ancient and modern style, can be a pleasant decorative element even inside the garden: it can be inserted at the beginning of an avenue or to interrupt a too compact hedge; it is also an excellent solution to support climbing plants with a showy bloom, such as roses, which, even on their own, always give a very pleasant ornamental note. A succession of individual independent arches can form a variant to the classic pergola, to be built along an avenue, to obtain a less intense shading. Many archers are built in bricks or even stones similar to those of the house, materials that have a more rustic and natural appearance, but, if the style of the house and the garden allows it, can also be realized in wood or even in live cement. In this case it is very complex to be able to give the construction the usual semicircular shape and it will be possible to resort to flat or corner cladding, which perhaps harmonizes better with the type of material; as has already been said several times, on several occasions, the modern designer ‘must take into consideration the character of the garden in which the arch or the arches must be inserted. The construction of a masonry arch requires great care not only in placing the individual building blocks in situ, thus harmonizing with the surrounding environment. In the front row, among the most exploited plants for this purpose, those climbers predominate, especially the roses, and among these the re-flowering forms. When the plants, once chosen, must be placed in the home, the holes must be prepared by digging them between one upright and the other of the pergola, at least 30 cm away from them or from the supporting wall, so that the roots do not interfere with the foundation structures that, over time, would lose their stability. The pit will be slightly wider than the maximum root development so that it has the maximum ease and does not have to branch off in inappropriate directions. The soil with which the hole will be filled again must be the most suitable for the cultivation needs of the chosen plants and, if the soil is particularly unfavorable, it will be necessary to perform a bonsai in good time. We mention some of the most used plants: Clematis, Jasminum, Passiflora, Lonicera, Wistaria, Ampelopsis, Parthenocissus, Bignonia, etc. (see Climbers, plants).