The Nativity façade: work prior to restoration

Soon the Nativity façade will be one hundred and the passage of time that marks people and everything else also deteriorates buildings. This is why, for some time now, we have been considering restoring it. This work will be left for a later time, however, as it is still in quite good condition. For now, though, extensive work has been done to detect any building issues, whether structural, such as cracks or fissures, or in terms of materials adhering properly, like the mosaics on the pinnacles. The façade is inspected twice a year.

Restoring a work like this, declared UNESCO World Heritage, requires a detailed preliminary study in cooperation with the top specialists. Gaudí’s disciples, the architects who took over from him before the current technical team, began studying this façade, making a quite complete collection of the floor plans, elevation and section drawings for the whole façade after the originals were destroyed by the fire in 1936. These plans in ink on parchment, as was common in those days, while well done would not be enough for a work of this magnitude today. So, in this line of compiling information, the work today has taken advantage of much more precise modern equipment to advance with the topographic survey, photogrammetric study and scanning of the whole façade. These three techniques will help us establish the scope of work to restore it.

Topographic surveying is a well-known technique used to map all the key lines and points in the geometry of the monument’s surface. This type of study provides a precise study of the conditions of the unique points and edges on this façade, in digital format, which makes it easier for us to incorporate the information into three-dimensional models.  Although it isn’t a new technique, the tools used have been greatly modernised, incorporating laser technology, automatic levels, digital data entry and digital extraction of the results. This study gives us the basic skeleton for later ones that provide more details, such as photogrammetry and scanning.

Photogrammetry is a technique that takes photos of the whole façade, moving the camera along the surface at a steady pace with a crane to take a shot every two millimetres. Although the pictures are flat, not three-dimensional, their importance lies in the information they provide regarding the colour and texture of the stone, and if there is any damp, efflorescence or pigeon stains.

The scanning of the façade, however, is done from various topographical stations on the roofs of neighbouring buildings, with omnidirectional emission and reception systems. These give us a cloud of points on the surface of the façade in detail that can be up to one point every 2 mm2 for the sculpture groups.

By combining all of these techniques, we can get a comprehensive three-dimensional view of the whole façade that is truly life-like and spectacularly precise.

LABORATORY TRIALS…

Another line of work currently under way, which could also be considered groundwork for the restoration of the façade, is the laboratory trials. In this regard, it is good to have reliable results from many different trials. So, everything from the method for extracting samples to their mechanical, physical and chemical strength must be tested, as well as getting the results from accelerated heating and cooling cycles, freezing conditions, wind, aggressive environments and pollution, etc.

… AND THE STONE

When Gaudí chose the materials for the Sagrada Família, he chose stone from Montjuïc for the whole outer face of the façade. This sandy stone gives us a wide variety of colours, thanks to its extensive chromatic range, and is also quite strong, much more than many other sedimentary rocks. This makes it a good stone to withstand the wear and tear of being exposed to the elements. For the inner face, however, as it should be protected from inclement weather, Gaudí chose a much lighter, softer stone. This ‘inner’ face, though, was exposed for many years and not properly protected until 2010, when the Temple was fully enclosed and consecrated as a Basilica. Any future works on this face will be determined by the restoration project.

All of this comprehensive preliminary work on the most emblematic section of our monument is being done, as we mentioned in the beginning, as the first step in considering the need for a full restoration of the Nativity façade in the future, from a comprehensive viewpoint that includes the inner and outer faces and the floors inside. So, broadening the aim and the sights of this preliminary work, we’re gearing it towards a future restoration project that will not skimp on technological or human resources, with monument experts.

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