Notre Dame Cathedral: A Case Study in the Perils of Restoring Fire Damaged Buildings

Posted on April 26, 2019

The fire and collapse of the roof on the Notre Dame Cathedral in Paris has been mourned the world over, and more than one billion (US) dollars has been collected to help restore it to its former glory. But what will that take? We talked with our President, Stephen Metz, who has experience in assessing fire damaged buildings over his 25-year engineering career, to get some information on what can be expected with a restoration of this scale.

A large renovation project with this much fire damage is fraught with risks, starting with figuring out the conditions of the building. Assessments are one of the most dangerous parts of a restoration. Sometimes safety is difficult to determine until you’re actually in the building. “It’s kind of a chicken-and-the-egg thing. Is it safe to be in? I don’t know, let’s go in it and see,” said Metz.

One of the many complexities of the Notre Dame Cathedral restoration will be the age of the building. When asked how its age will exacerbate the normal challenges of restoring fire damaged buildings, Metz said that the condition of the materials the structure was built with has the most influence on how difficult it will be to rebuild.

“When you get into old buildings like this - I mean, Notre Dame is 850 years old, we don’t have anything that old around here - but even around here, when you get into buildings that are 100-years old or so, it’s almost always some sort of masonry wall - brick, stone, or what have you - and the condition of that comes into play, which is all about how well it was maintained and how well they kept water out of it during the life of the building.”

One might think that since the cathedral’s exterior was stone, it would be fairly safe from fire damage, but Metz cautions against that assumption. “The stone can change in composition when exposed to fire… Pieces of structure support other pieces of structure. In many cases, the roof stabilizes the walls. If the roof isn’t there anymore, are the walls still stable?”

In addition to the damage done by the fire, there are many instances where putting it out does more damage than the fire itself. There is also more environmental damage that can still be done between now and the end of the restoration process. When asked what the first step in the restoration will be, Metz said they’ll most likely put up a temporary roof to prevent water infiltration and seal the building from the elements. “There probably isn’t going to be a lot of water damage in the masonry and stone, because that should dry out on it’s own. But it might be a year before any real work to restore it gets started, and the weather conditions in that period of time could cause further damage.”

Metz says that depending on the extent of the damage, it’s usually more cost effective to rebuild, but that this is an obvious exception. However, the question remains, what kind of restoration will it be? Will the building be a purely historical restoration, or will it incorporate modern elements that would bring it up to code? Metz notes that, “When you have a building that has this much history, which period do you want to choose to restore it to? It’s changed multiple times over 800-some years, and a lot of the changes probably aren’t even documented. Even the famous spire was only 150 years old.” If it is designed to modern codes while trying to keep its historic aesthetic, this adds a new layer of complication, planning, and costs. Questions about where things like modern lighting, HVAC, and sprinkler systems will go and be the least visible.

Ultimately, it’s difficult to tell what the restoration of Notre Dame Cathedral will require, and what modern amenities they will use on the rebuild. One thing that Metz says with certainty is, “Whenever you get into old buildings, there’s always the unknown. Fortunately, there are very good people who have experience in work like this. I’m sure the end result will be a good beginning for the next chapter of Notre Dame.”