ONGOING WORKS AT THE HAGIA SOPHIA GRAND MOSQUE CONTINUE UNDER THE DECISIONS OF THE SCIENTIFIC COMMITTEE AND THE CONSERVATION BOARD

The works initiated to ensure that the Hagia Sophia Grand Mosque — which has stood for nearly fifteen centuries and has been destroyed and rebuilt three times — is transmitted to future generations in the most accurate and structurally sound manner continue under the supervision of our Directorate General. Within the scope of the second phase of restoration works that began in 2023, the exterior lead coverings of the main dome are being renewed to enhance Hagia Sophia’s earthquake resilience. During this process, the Scientific Committee and the Conservation Board decided to temporarily cover the dome surface with a steel construction to protect the structure from seasonal conditions and prevent damage to the interior mosaics.

In line with this decision, the Scientific Committee approved the construction of four main columns, each 43.5 meters high, inside the mosque in a manner that does not impede worship. It was determined that installing the 43.5-meter system and transporting steel materials would require the use of construction machinery, and a dedicated access route was planned from the western side of the structure. Accordingly, static load calculations, ground load tests, soil classification tests, and georadar scans were carried out. Following these assessments, the load-bearing capacity of the ground was calculated as 25 tons per square meter, while a system with a 30-ton per square meter capacity was built as a protective measure. The machinery to be used in the project was selected based on these parameters. The heaviest planned vehicle weighs 45 tons, and its load distribution equals 6 tons per square meter. The specially prepared ground is fully capable of safely supporting this load. After nearly a year of preparatory work, the technical projects were finalized, and implementation began with the approvals of the Scientific Committee and the Conservation Board.

A steel platform supported with precast elements and wooden components was installed — in full compliance with static calculations — across the entire area from the western courtyard entrance to the mosque’s prayer hall, including the garden and the inner and outer narthex sections. This system both protects the marble flooring and prepares the area for vehicle access. In the prayer hall, the existing marble flooring was first documented, and the bedding mortar beneath the marble slabs was inspected. Georadar scanning and soil classification tests were subsequently performed inside.

Following these preliminary studies, a multi-layered temporary flooring system was installed across all areas where construction machinery will move, ensuring both load distribution and the protection of the marble slabs. To prevent damage to the original marble flooring of Hagia Sophia, a complete protective system was applied in layers:

• a vapor-permeable membrane,
• felt,
• sand,
• 18 mm plywood,
• a 10×10 cm wooden frame,
• XPS insulation boards placed between the frames,
• a sound-absorbing underlay on top,
• and finally, a diamond-patterned steel sheet as the uppermost layer.

This layered system ensures full protection of the historic marble surface. During the works, smoke extraction devices are also being used to prevent the spread of exhaust fumes from construction machinery.