Restoration work at Istanbul’s Hagia Sophia Grand Mosque is entering a new phase, with a steel platform to be installed inside the eastern half-dome for structural reinforcement and conservation work.
The eastern half-dome has been identified as the most vulnerable part of the historic structure based on modeling and structural analyses. Experts say it could be the first area to collapse in a major earthquake scenario.
Professor Hasan Fırat Diker, an architect and member of the Hagia Sophia Scientific Committee, said the work would continue while the mosque remains open for worship and visitors.
“The main dome is completely covered on the outside. We will continue this process in the eastern half-dome and observe the interventions that need to be made,” Diker said.
The main dome is supported by four large arches, with the arch connecting it to the eastern half-dome considered the most delicate, Diker said.
“We had to give priority to this area,” he said, adding that restoration would continue both from inside the structure and from above.
The project is considered the most comprehensive restoration of Hagia Sophia during the Republic era. Unlike earlier repairs, which largely involved interventions in specific areas, the current project addresses both structural issues and the conservation of the building’s original decorative elements.
Mehmet Selim Ökten, a civil engineer and member of the Scientific Committee, said numerical modeling and analyses showed that the main dome needed to be reinforced together with the half-domes.
A scaffolding system and a membrane-covered protective dome have been installed to allow the work to be carried out safely and in accordance with conservation procedures, he said.
The steel platform and scaffolding will also facilitate conservation work on Hagia Sophia’s mosaics. Professor Ahmet Güleç, a materials scientist and chemist, said experts had already begun inspections, cleaning and protective work on the mosaic surfaces inside the main dome.
Once sections of the main dome’s lead covering are removed, samples of mortar, plaster and other building materials will be collected and analyzed to determine which materials to use in subsequent conservation work.
Alongside the structural reinforcement, conservation work will be carried out on mosaics and painted decorations inside the eastern half-dome. Marble surfaces on the eastern mihrab wall will also undergo cleaning, conservation and repair.
Art historian professor Asnü Bilban Yalçın said Hagia Sophia has undergone repairs throughout its approximately 1,500-year history because of structural problems, including during both the Byzantine and Ottoman periods.
She said the latest restoration aims to strengthen the dome, half-domes and exedra using modern knowledge and technology while allowing experts to study parts of the structure that remain poorly understood.
Architect professor Can Şakir Binan stressed that structural safety must be balanced with preserving Hagia Sophia’s historical layers and original materials.
“Structural safety is, of course, a priority,” Binan said, adding that this should go hand in hand with protecting the mosaics, painted decorations, marble surfaces and traces of earlier repairs that form part of the building’s identity.
He said interventions should be based on scientific research and detailed documentation, with as little intervention as possible and original materials preserved in place whenever possible.
“The aim is not to return Hagia Sophia to a particular period, but to preserve and carry into the future its unique multilayered identity, authenticity and integrity shaped by 1,500 years of history,” Binan said.
The restoration is being carried out by the General Directorate of Foundations under the Ministry of Culture and Tourism, in line with decisions by and under the supervision of the Scientific Committee and Conservation Board.
Work on the main dome, including mosaic conservation, dust removal and temporary protective “facing” of mosaic surfaces, is ongoing. A temporary steel roof has also been completed over the main dome, while work continues to carefully open sections of its lead covering.
The installation of the steel working platform inside the eastern half-dome will mark the next stage of the restoration, which authorities aim to advance without disrupting Hagia Sophia’s use for worship and visits.
