Koimisis Tis Theotokou Greek Orthodox Church, known as Panagitsa, was deemed to be unsafe and dangerous by city officials and engineers who carried out an inspection.
As a result, parts of the roof were removed over the weekend.
The fire broke out on April 13, and it took about 75 firefighters several hours to put out the violent flames.
The fire damage was so bad that almost all of the building will need to be demolished right down to its foundations.
The bell towers were taken down — and saved for when the church is rebuilt. A few items inside the church were also salvaged.
"Certain icons on the side of the church have been removed already for safe keeping," said Pelagia Adamidis of the Hellenic Community of Greater Montreal.
A small chapel in a newer wing of the building won't have be demolished.
People in the Greek Community in Park Extension said more than a building has been lost.
"You can put a dollar figure on the walls, on the wood to build it, but you can't put a dollar figure on what's inside — the art, the iconography, the memories," said Greek-Montrealer Christos Hatzimarkos.
Some in the community had hoped that they could continue to attend outdoor mass at the church.
The city had given permits for them to hold a vigil after the fire, but that won't be possible during the demolition and construction of the church.