On the occasion of Pope Francis's visit to Chile, the Metropolitan Cathedral Chapter requested conservation work on the Cathedral's vaulted ceiling to improve safety and the condition of the ornamentation after recent earthquakes, aiming to safeguard the many faithful who visit the Cathedral daily.
The firm Grupo Predio was commissioned to carry out the restoration and conservation of the cathedral's central vault and the tabernacle chapel. The company has specialized in heritage restoration for over 15 years, with extensive experience executing unique works of art and architecture in heritage sites and historic districts (Zonas Típicas), collaborating with both public institutions—such as the National Monuments Council—and private organizations.
Notably, the vault had not been accessed since Eusebio Celli's repairs in 1906, an opportunity that revealed the ceiling paintings are actually frescoes. In addition, the cracks were treated using reversibility criteria, allowing for future modifications.
Grupo Praedio Description: The commission presented an engineering challenge, as reaching the vault's ceiling was no simple task. Two machines capable of reaching a height of 20 meters were required to assess the condition of the cracks, which appear small from the ground but are visibly major up close.
Another operational challenge was that the maintenance had to be completed within 30 days without disrupting Eucharistic services. Consequently, the team had to be small and work in absolute silence, respecting the sacred nature of the space.
An even greater challenge was the need to achieve a high impact in terms of aesthetics and safety in the most efficient timeframe and under budget constraints. This called for an assertive and innovative approach, requiring an error-free conservation strategy aligned with the highest heritage standards: reversibility in conservation.
During the Process
To operate the machinery inside the Cathedral, a wooden structure had to be built to redistribute the weight of the mechanical booms across the floor. Because there is a basement level underneath and the upper floor structure is quite delicate and old, it could not be relied upon to support the weight of the machines. Additionally, the floor was covered with cement tiles that could be damaged by the machinery, so MDF panels were laid down to protect them.
The maintenance work had to be planned in stages and coordinated with the machinery, as the cranes had to be moved simultaneously across the vault to follow the established workflow within the estimated timeframe.
The scope of work included patching cracks and fissures and consolidating structurally affected areas using plaster, expanded metal mesh, and oakum. For color matching, pigments and additives were used to harmonize with the base color, setting the stage for full color matching in a later phase.
Regarding heritage preservation, the criteria applied centered on the reversibility of the materials. In other words, all conservation efforts were carried out in a way that ensures the maintenance interventions are reversible, leaving room for a full restoration in the future.
Historical Overview
The Cathedral of Santiago is one of Chile's most iconic buildings. It stands out not only for its scale, construction, and history, but also as a fundamental part of the nation's identity.
The church is located alongside the Plaza de Armas. In fact, when Pedro de Valdivia founded the city and laid out the grid plan to organize the urban area, he allocated a prominent site for the church, reflecting the immense importance of Christianity to the Spanish crown and the conquistadors.
Naturally, the Cathedral we know today is not the same one erected in the 16th century; it underwent numerous modifications over the years. Experts generally identify four major historical stages:
First, a primitive stage, spanning from the initial construction in 1541—including numerous failed attempts to keep it standing—until the 1730 earthquake; second, a stage marked by the significant modifications of Matías Vásquez de Acuña; third, the contributions of architect Joaquín Toesca; and fourth, the final transformations by architect Ignacio Cremonesi. Thus, the church evolved structurally from adobe, ashlar stone, and brick to steel and reinforced concrete. Spatially, it developed from a small, post-and-beam interior to a three-nave layout, featuring a taller central nave topped with barrel vaults and fully finished walls designed to accommodate profuse decoration.
Today, the Santiago Cathedral welcomes a large number of local and international visitors who attend masses, religious festivals, services, and other liturgical activities. Others visit to experience its architecture, construction, and design, as it is a prominent Neoclassical work. In the mid-18th century, following a fire that affected the Cathedral, architect Joaquín Toesca was commissioned to design the facade and the Church of the Sagrario, a process that was completed 80 years later.
During the construction period, Eusebio Chelli and Ignacio Cremonesi also contributed; the latter lent a Tuscan and Roman character to the heritage building, adding two towers to the facade.
The Santiago Cathedral, a building of approximately 4,500 square meters, is a massive undertaking whose construction embodies the history of Chile. Its value and importance lie not only in its connection to the Catholic religion, a foundational pillar of local history, but also in its cultural, traditional, and historical significance.
Restoration Process Description
Commission: Repair of cracks and fissures in the barrel vault of the Metropolitan Cathedral.
Intervention Proposal by Grupo Praedio
Methodology:
- On-site methodological review.
- Data collection throughout the process with a future restoration in mind.
- Repair of major cracks and fissures, defined according to CMN and international standards.
- Color matching of the plastered cracks so as not to highlight the temporary solution, blending with the current condition.
Timeline:
- Execution of works within 30 working days.
Logistics:
- Use of two articulating boom lifts due to the intervention height and versatility of movement.
- Perimeter enclosure across six colonnades.
Challenges:
- Tight schedule, high expectations for the intervention.
- Respect daily liturgies and large-scale celebrations.
- Intervention height: 18.5 m.
- Use of two 7,300 kg articulating boom lifts.
- Intervention with minimal impact on the existing infrastructure.
- Construction of custom-built platforms to distribute the loads of the articulating boom lifts.
- Definition of the on-site intervention methodology.
Definition of Existing Pathologies:
The main forms of deterioration found in the specific area of intervention (interior, central vault, and perimeter above the continuous cornice):
- Impregnation and deposition of dirt (Pollution and Soot).
- Dirt accumulation across all facade ornamentation of the building.
- Material degradation (Oxidation and Corrosion).
- Oxidation and corrosion of the existing mesh used to anchor the concrete plaster.
- Material spalling and detachment.
- Peeling of coatings and paint from its ornamentation.
- Fractures, fissures, micro-fissures, and cracks.
- Missing elements.
- Moisture condensation.
- Successive layers of paint.
This article was written by Fernanda Amaro. The translation is powered by AI.
