The construction of the fortress of Serón de Nágima (Soria, Spain)

This fortress is named many times during the late medieval confrontations between Castile and Aragón. That responds to the fact that it is located in one of the busiest routes between Jalón´s and Duero´s valleys in the “Two Pedros War”.

News about the city of Serón are dated since 12th Century, but it is possible that the castle were built later in the 14th of 15th Century. However, many investigators has dated the castle as muslim, that is: previous to the 12th Century when the territory is reconquered. The reason for what they have dated the castle is its constructive technique of rammed earth, because there is any artistic element. We think, comparing the construction with other castles of rammed earth, that the erection of the castle was around the Late Middle Age and in only one constructive stage.

The castles from the south-east

The walls are 2.40 m width at the lower part and 2.70 in the upper. The difference leads us to think that a skirting board protected the lower part of the wall. It could be ashlars masonry. The upper part of the wall has an outer layer of lime mortar coat about 10 cm thick, commonly known as calicastrado. It is built by rammed earth levels around 90 cm high. Batches of compacted earth can be observed. The average thickness is between six and seven centimeters.

The presence of the putlog holes of the wooden cross ties helps us to reconstruct the proc­ess of the walls construction. The distance between these putlog holes to each other is about 70 cm. They pass ever from one side of the wall to the other side. In some of them, the superficial sealing remains. This stopper is made with a fill of rubble, gravel, mud and lime. None of them shows any rest of the wooden cross ties. These signs are the negative of the wooden beams used both as wooden cross ties of the formwork as scaf­folding to build the walls. Two wooden cross ties’ sizes have been documented: 8 x 15 cm and 10 x 10.

West wall of the castle of Serón de Nágima

The upper part of the walls was finished off with lime mortar rubble, constructed with the same tech­nique of rammed earth formwork. This way, the head of the wall would be protected from impacts and erosion with a more resistant material.

In the walls preserved from the Serón de Nágima castle, we can see several voids. In the western wall there is a big high hole, which could have perhaps been the access to the site. However, the most ex­ceptional holes are some aspilleras or saeteras —loopholes or arrowslit: defensive holes with vertical form—formed by a formwork inside the rammed earth.

The encounter among the several phases of the building is done by a inclined joint. It is the result of the shortening of the length of each batch. In this manner ensures proper interlocking between the different phases of work. The inclinations of the different joints are parallel.

For further information:

Rammed earth walls in Serón de Nágima castle (Soria, Spain): Constructive lecture
http://oa.upm.es/11373/