The dome of the Four Courts in Dublin is to undergo extensive repairs after it was found that rust was beginning to corrode part of the structure.
The Office of Public Works has said that the specialist repairs will begin immediately.
The work is expected to cost approximately €1m and will take place over two years.
Minister of State Brian Hayes has said there is no immediate danger to the structure, but that the dome had suffered extensive damage as a result of a fire during the civil war in 1922.
It is hoped the work will preserve this part of the iconic building, he added.
In 2011, a section of one of the column capitals fell on to the roof of the Four Courts below.
In investigating why this happened it became clear the cause was the rusting of a steel angle immediately above the capitals of the columns supporting the dome.
Mr Hayes said: "There's no danger whatsoever. The courts will continue, the main visible difference for people is that they'll see enormous scaffolding around the dome for the next two years but people should be confident to know that the work going on will preserve and protect this building into the future."
The repair work will be done in collaboration with Trinity College Dublin.