Challenges await Notre Dame Cathedral restorers

The challenges for Notre Dame Cathedral restoration include finding ways to integrate new material into the old existing structure, according to a leading historian at Cambridge University.

"In terms of the interior fittings and the roof and spire, it will be new - while the shape and stone body is the same - so it will be both the same Notre Dame, but also with new materials and building," said Alan Macfarlane, professor emeritus at King's College, Cambridge.

While most of the cathedral's roof and its spire were destroyed by the fire Monday evening, the main structure of the historic building, including two bell towers, was saved by a team of firefighters within a crucial time window of 15 to 30 minutes, according to French authorities.