a wooden mold. Due to its insulating power in extreme climates, this ancient procedure has been used by the Arabs to solve their housing problems. In the Somontano of Huesca, as in the entire Spanish geography, mud-brick constructions stand out in the rural landscape, either alone or combined with adobe, stone or brick. The clay construction technique, which has remained practically unchanged through the centuries, today hardly has any representatives who know how to carry it out. To learn about this process, we have asked Hilario Artigas in the town of Agüero, to build a small garden house, just like the ones he built with his grandfather, a master bricklayer, until a few decades ago. This construction, which has begun with the cleaning and leveling of the site, has as its starting point the elevation of one of the pillars, based on ashlars joined with mud. Its leveling is guaranteed with the perpendicularity of the plumb line. The stone pillar will serve to mark the starting position of the formwork boards. These boards, without fixed measurements, used to be one and a half meters long by one meter high. Its fastening to form the formwork box was made by means of crossbars called "cuairons", which gave a separation of half a meter, or the measure that the architect wanted to give the wall thickness. The closure of the free side of the formwork was done with a wooden board called "chopping board", which in turn, prevented the boards from joining each other. Normally, houses built with mud, were raised on a base of ashlar masonry approximately half a meter high. For smaller buildings, a layer of stones at the base protect the wall from soil moisture. The soil to be used in the construction of the rammed earth is the one that facilitates the environment itself, having clay and a lot of stone as an essential characteristic. As the masters in the field say, the earth must have a lot of "gravel", because the gravel is the support of the wall. The tamper is a block of wood, weighing 6 to 8 kilos, with a round base on some occasions and a square base on others. The truncated-pyramidal shape allows the "tamper" to be better adjusted to the corners of the formwork, better "attacking" all the corners. Fill the wooden box with several layers of packed earth, and once each block of mud is finished , the formwork is dismantled to advance laterally in the construction. The compacted earth block, exposed to the elements, will progressively lose moisture, in turn gaining consistency. The assembly of the formwork for the manufacture of the adjoining block is carried out by mounting the boards on a piece of anterior wall. The process is repeated with the same technique for each of the blocks: layer of earth ..., watered with water ... and tapping with the "ram", until flush with the formwork. The small layers or layers 8 or 10 centimeters high of "cascallo" soil, slightly moistened, require great skill and practice to be packed with the blow of a mallet or "ram". "Attacking" is called this work of continuously hitting the layer of earth, uniting all the particles until leaving a compact and resistant mass. The thud of the tapping of the "tamper" indicates the moment in which it is convenient to add a new layer of earth, revealing in turn, any failure in the quality of the tread. Like the beginning of the wall, the closure is made by raising a pillar of ashlar masonry. In addition to the knowledge of working with the earth, the master mason had to know the technique of carving stone as a constructive element. Adapting each stone block to a specific shape and structure requires a minimum knowledge of stonework. The plumb line, a faithful ally of the bricklayer, guarantees the perpendicularity of the construction. Building with earth is not limited only to mud. Its combination with other elements of the same raw material, such as adobes or bricks, can be seen in many of the constructions of this type. The mud blocks of the upper row are placed alternately with those of the lower course , avoiding that the beginning and end cuts of the new blocks coincide with those below. Thus, the center of each upper block must coincide with the junction of the two lower blocks. This alternate placement guarantees a greater solidity of the entire building as a whole, avoiding possible openings. A good bricklayer must have hard arms and a lot of drive. To prevent the soil from getting muddy and sticking to the mesh during tapping, after "ruching" the layer of soil with water to moisten it, a light layer of dry soil is added. In spite of this, normally, the damp earth particles remain fixed to the base of the "ram". For the manufacture of the mud from the union of the stones of the pillars, the same type of earth is used as for the mud, once it has been gripped to leave the finest particles. The stones of the pillars are placed, stepping on each other, and starting from the corner to the sides. The stone that fills the empty space is called "trescantón" and serves to maintain the horizontality and balance of the pillar. The pressure of the caked earth on the formwork boards is so great that it forces to leave in their manufacture, a small separation between each of the boards that compose them, through which the humidity and the force of the earth escape, preventing let the boards fall. The earth used in the construction of mud, was sometimes mixed with dead lime, to obtain a strong and resistant mortar. Some master masons tore up the earth they were going to use before winter, and left it in piles to be "cooked" in the open air, aerating it from time to time. Unforeseen storms and rain become a fatal enemy during construction. In such cases it was necessary to protect the piece of construction made from water. Once the mud was dry, its resistance to all kinds of inclement weather was remarkable, as the passage of time has shown in the centuries-old constructions. The upper row of tapieras and the lower row are differentiated by a layer of stones placed at will, and by the holes left by the "cuairons" or crossbars when they are removed. Pine or fir logs, selected to the appropriate size, are the most appropriate to support the entire roof of the house. All deciduous trees are dwindling, and evergreens growing. If, in addition to not being cut on the corresponding moon, it is done in the "wise" season, that is, in spring, to prevent them from spoiling, the bark must be removed from each of the trunks. The "chinibro" or juniper wood, due to its resistance to the elements and inclement weather, cut into a square, is the most appropriate to make the overportal. Generally, and within the simplicity that characterizes this type of construction, the roofs are gabled. To do this, the main and rear facades must end in gable, bearing the corresponding unevenness , which is usually 35%. Making the knife is called the configuration of the walls that will shape the roof. The central beam of the roof, stronger than the others, is called the "bridge". Once fixed on the vertices of the gable end of the building, it will receive the weight of the rest of the timbers on it. The transverse beams are placed maintaining a uniform distance between them, and supporting one point on the "bridge" and the other on the side walls. The separations of some timbers with others are closed with adobe blocks. The boxwood or bucho, due to its hardness and resistance, constitutes an excellent base for laying tiles. Due to their transversal arrangement, on the timbers placed in the direction of the water, the buchos constitute a framework of poor heat conductivity. The tile used for the total closure of the roof is corrugated, normally called "Arabic tile". Their arrangement is made in rows of pieces with their concave part facing upwards, forming channels to collect rainwater and lead it outside the building, alternated with superimposed courses with the convex part facing upwards, in such a way as to pour the water into the contiguous courses. In some buildings, the construction was finished with the plastering of the walls. For this, a mixture of sand and water with hydraulic lime was used, which acted as a binding binder. The application of this mortar increased the strength and resistance of the walls against inclement weather. At present, the construction of rammed earth walls is practically abandoned. The sense of speed and practicality prevails today over the multitude of advantages that this type of construction has shown throughout history: - Technological autonomy with low-cost materials. - Ecological stability with minimal energy input - Durability over time. and above all, its insulating ability from cold and heat.
