- What are the best materials to use?
The choice of the type of material to be used depends on various parameters: the local tradition, the climatic conditions of the place, the use, the budget, the availability of materials and skilled workers, the amount of future maintenance, etc. However, each place has its own peculiarities, which must be investigated and studied to better understand its formal characteristics, customs and contaminations. Each stone used has its own customary use, which depends on how it will be used and the final destination; furthermore the stone elements must be sized in relation to the stresses they will have to withstand. When combining various materials, the physical-mechanical characteristics of the same must be taken into account so as not to combine stones with incompatible characteristics.
- What are the drawings, the figurations to be used to characterize the future shapes?
Once the types of materials to be used have been identified, or even during such step, it is necessary to imagine and ponder the type of design and figuration intended for a specific area. In historical centres, it is almost always necessary to comply with the classical character and traditional figurations, in order not to contrast too much with the pre-existing flooring and buildings. It is therefore advisable to resort to traditionally consolidated formats, which relate to the historical functions of spaces and buildings. To this end, it is necessary to carry out a study as in-depth as possible on the traditional use of materials and flooring that have historically been present. If traditionally, as it happened in many places in Italy, the driveways were marked by trotting tacks that facilitated the advancement of the wagons, these can correctly be re-proposed. For example, if the surfaces are irregular and the surroundings are rather essential and devoid of particular ornaments, it will be better to use materials such as porphyry cubes with overlapping arcs or cobblestones, which are well suited to any type of location and setting. On the other hand, the presence of particular architectural features and decorations on the buildings, or the dimension of the spaces may suggest a more characterizing design, offering more complex and structured figurations and equipment, always in line with the formal characteristics of the intervention spaces. Another aspect to keep in mind when dealing with surfaces with a high level of use is the comfort and safety of pedestrian traffic. The support surface must be as comfortable as possible for all types of footwear as well as for disabled users and their means of transport. In any case, flushing (smooth and shiny) is not recommended, since such surfaces become slippery in wet conditions, and are therefore dangerous to walk on. Once the flooring has been configured with all its elements, it is time to proceed with the sealing. The purpose of such operation is to close all the interstices between the elements of the flooring thus making them solid, leaving the surface perfectly clean and the stone element prominently visible. Its function is often underestimated, but it is a fundamental operation, both as regards the physical-mechanical strength of the flooring system, and its performance from an aesthetic perspective. The slabs are usually sealed using the so-called “cement grout” technique. In short, this technique consists in mixing cement, clean water and fine sand in equal parts, until a semi-liquid compound is obtained. This will be applied over the entire flooring and, once it has penetrated to close all the empty spaces, and has reached the right state of consistency and maturation, it will be cleaned up to leave the surface of the stone elements perfectly clean and free from any residue. For cubes instead, it is possible to use only sand until all the interstices are perfectly filled: this is the technique normally used for historical flooring.
- How should a flooring element be laid and tamped down?
First of all, some guiding elements (the “points”) must be juxtaposed, which serve as a reference for the floor area and the alignments. After being positioned with the help of various tools and spirit levels, they form the basis for lines and special ropes that will help installers to position the flooring elements correctly. The slabs must be hit hard with special rubber hammers until they are positioned at the right height and in their correct seat. The cubes and cobblestones, on the other hand, must be positioned at a level that is slightly higher than the final one, since they will need to be “beaten” down. This is a settling process carried out through mechanical tamping that varies in degree according to the size of the flooring elements. Once placed, but before beating, the cubes and cobblestone must be submerged in a mixture of rather fine sand and cement, which, following abundant wetting, will set and secure the lower part (base) of the flooring elements.
- What is the best bedding system for stone elements?
The bedding layer is placed above the substrate in order to support the stone elements making up the flooring. It is the layer that directly houses the stone part of the flooring and is therefore very important and crucial for the overall success of the works. The thickness of this layer can vary from four to seven centimetres, depending on the type and size of the lithotype. It generally consists of a mixture of sand with an appropriate grain size and Portland 325 type cement in quantities ranging from 250 to 350 kg. per cubic metre of inert material, depending on the use and lithotype employed. When laying slabs, the compound must generally have a consistency similar to moist earth to increase its adhesion and workability qualities. A semi-liquid compound, called cement grout, obtained by mixing equal parts of cement, clean water and fine sand must be spread over the lower surface of the slabs. This operation greatly increases the degree of adhesion and makes the slab integral with the underlying layers. In the case of cubes or cobblestones, the bedding layer can consist of sand of suitable granulometry, or sand mixed with cement in quantities of no less than 300 kg of cement per cubic metre of sand. If the sand-cement compound is used, attention must be paid to the compound mixing operation: in fact, the compound must be homogeneous in all its parts, in order to avoid different degrees of resistance of the paved surface.
- What is the difference between porphyry from Trentino and Argentina?
The mechanical properties (resistance to compression, bending and flexion, freezing, etc…) of the two materials are very similar. The differences are found in the colours: porphyry from Trentino is grey-brown, whereas the Argentine porphyry embraces a wider range of hues that includes various shades of grey and red.
- What is the difference between the flamed textured surface and the quarry surface?
The quarry surface is the natural surface corresponding to the natural slab surface of the rock, which may come in various thicknesses ( 1-3, 3-6 cm etc…), depending on the natural predisposition. The flamed textured surface, instead, is obtained from a slab cut from a block: in this case, the thickness is constant as it is the result of the block being sawn. From the sawing of the blocks it is possible to obtain slabs of the desired thickness and, unlike the natural quarry surface, it is possible to obtain very large slabs suitable for various types of works, including ventilated walls with large modules. Flaming is obtained by processing the sawn slab with oxyacetylene equipment and allows enhancing the colour and brightness of the material.
- How much space do you need between the concrete slab and the material, including the bedding, that will be laid, that is the surface area?
It depends on the type of material that will be installed. For example, for cubes that are 6/8 cm thick, the spacing must be at least 12-14 cm, whereas for those that are 8/10 cm thick, at least 15 cm are required; the space needed for quarry surface tiles with a thickness of 3/6 cm, is at least 10 cm.
- Which material is recommended for a road characterized by an average vehicle traffic?
The most appropriate material in this case are cubes with a minimum thickness of 6/8 cm, and tiles with a thickness of not less than 3/6 cm.
- What is the best rainwater disposal system?
Every system concerning flooring cannot ignore the relationship with the atmospheric events that will affect that surface. For this reason all the necessary measures and precautions must be taken to make the rainwater drain as quickly as possible, making the surface usable even in adverse weather conditions. The slopes for the disposal of water must be carefully studied and applied during the execution of the works. Each stone material can undergo machining or surface treatments that vary its degree of roughness, and therefore the speed of outflow of surface liquids. Even the formats, that is the dimensions of the slabs, affect the speed of disposal, and more particularly, the smaller the format, the lower the disposal capacity, as the grout lines are an obstacle for liquids that are trying to flow, which slows down disposal speed. Therefore, along the water flow lines (water trenches or drainage gutters), it is advisable to use materials of suitable size and with a surface that is as smooth as possible. The general slope of the paved surface will in any case depend on the type of stone material, the surface treatment adopted, the format of the flooring elements and their arrangement. On outdoor surfaces, however, the slope for surfaces paved using slabs should be no less than one and a half percent (1.5%), and no less than 2% if cubes are used. The slopes must not be lower to ensure a rapid outflow of rainwater, which is always recommended with intense pedestrian and vehicle traffic; this also prevents small or very small stagnations in limited portions of the surface, always possible given the craftsmanship of the operations that can give rise to some small instability.
- Why choose natural stone over cement and synthetic products?
The discovery and use of stones for construction work date back to several thousands of years: in fact, important remains and monuments have been found in Assyrian, Babylonian, Egyptian and Roman sites, which are the cradles of our civilization. The use of natural stone over the millennia makes it a reliable and tested product, whose performance has been known and recognized for centuries.