Will the computer become the rescue for the Notre Dame? (1)

A disaster with far-reaching consequences

After some time, this will be old news already, but for now, this remains fresh in everyone's memory: a huge fire made the roof of Notre Dame in Paris collapse, at 15 april 2019. During the current restoration a fire broke out somewhere around the base of the spire, which, along with the rest of the roof, burned down and partly fell on the scaffold, and partly on the vault beneath. Part of the ceiling collapsed. All technical terms which I will explain later on.

It surprised me how much I was shocked by the first television pictures of the burning cathedral. It is again clear that this is not just any French church somewhere , but an iconic place that belongs to the heritage of the world. Yet it is strange that the fire in this building evokes more emotions than a war or a famine on television. It's ultimately only a material object that was made for mankind. Is the human being then not more important?

A very short time frame (1)

French President Macron announced the next day already that the church will be rebuilt, and even within a period of five years. That's quite a bold statement: for example, for just the Utrecht Dom tower there are also scheduled five years of restoration, and that is in a lot better condition than the much larger Notre Dame.

I think that Macron on the one hand could not estimate how very much work this restoration would be, but he must have also thought: "Better aim high and closely miss the target, then target too low and create a lingering eyesore.’ I suspect that most people know how much work has been put into building these cathedrals; often hundreds of years had passed before a cathedral finally was 'finished’ years old.

From a way too tight budget to a huge budget

Now Notre Dame was under restoration at the time of the fire. The whole church needed to be restored, but there was not enough money. At the time of the fire the central tower (the spire) was being restored for 6,8 million euros. Notre Dame is one of the many thousands of monuments that France can boast of, and they all have to share the funding with numerous other candidates which are in equally bad shape, or worse. There also was a lot of maintenance and a first estimate was that a restoration would cost about 150 million euros. That still seems like a relatively low estimate: for the much smaller St. Eusebius's Church in Arnhem (the Netherlands) some 27 million euros were needed (though at first it was thought that 96 million was needed). After the fire in Paris, suddenly a floodwave in grants came forth and the counter is already at over a billion. You'd think that it should be about enough to do the job.

Three restorations in one

But in fact it's not just one restoration here, but three. Firstly, Notre Dame was hard in need of restoration already. In such a restoration usually especially the roof, the windows and its natural stone are tackled. The problems will then lie with the weathered roofing, rotten wood, worn glass-glass, and the replacement of rusting iron parts Window, and weathered stone parts, broken natural stone and missing parts. Often, the natural stone was also originally mounted with iron pins, which started to expand because of rusting , causing damage to the stonework surrounding it.

Secondly, because of the fire many parts have been lost. The roof has collapsed, a part of the vaulted ceiling has fallen down, the wooden central tower is gone, etc.. That will have to be brought back.

Thirdly, the fire has caused damages to lots of other parts. Stones that have been exposed to a hot fire for a long time can turn to dust on contact. There will also be water damage, and there will be parts that still seem usable but on closer inspection will have to be replaced anyway.

The architect

Such an extensive restoration requires good management. Especially with such a huge budget there will be a lot of people who get dollar signs in their eyes and hope to snatch a handful from the big pot. In the olden days, the cathedral building would have been led by a master builder. Someone who had gone through the whole training of stonemason and sculptor to architect, and knew all the ins and outs. He knew his materials, knew all of the required quality and had enough authority to manage everything smoothly.

It is sometimes said that in any commission three variables apply, and that you can only have two at once: fast, good and cheap. With so much time pressure on it, the last variable already died, and I fear that if not controlled tightly, quality too will dearly suffer under the haste. Menawhile, Notre Dame stands out as a prime example of the extremely high quality of the 19th-century restoration wave.

Viollet-le-Duc

In 1844 the cathedral was about to collapse. A comprehensive restoration plan was led by the then young architect Eugène Viollet-le-Duc. During that restoration many details were added to the church, which had have never been there before, such as the chimaeras on the balustrades of the two towers. Later critics this would probably like this to be reverted to a stage with more medieval elements, but it should be said that both technically and artistically that restoration was of very high level. Said restoration work, plus the writings of Viollet-le-Duc, have inaugurated in many countries a revival of Gothic architecture: the Gothic Revival. In the Netherlands it was mainly Viollet-le-Ducs admirer Pierre Cuypers that shaped the Gothic Revival. So with this legacy Notre Dame was both burdenend and enriched. It sets the baseline for the quality of the current restoration. You can not put a load of clumsy and inept modern work between the delicate neogothic ornamentry without seriously compromising the church. The task at hand is to do everything to approach that quality and that of the original Gothic work. It will be the job of the restoration architect to maintain a high quality in this.

Mapping it all out

The first task will be to chart every detail. What is still left, what is damaged, what should be replaced? From 1999 to 2010 I participated in the last major restoration of the St. John's Cathedral in 's-Hertogenbosch (and afterwards in smaller restoration phases). In such a restoration each facade, every window, each and every buttress flying buttress receives a number, and within those main components each piece of stone regains its own sequential number. Each block is put on a drawing and of each block is known what should be done with it: keep it, replace it or repair it. And that's just the chapter stonework! It may be clear that this requires some tremendous planning. At St. John's Cathedral, since the 90s digital mapping of each facade has been applied. Already in those years, the stone blocks were drawn in the computer in 3D CAD. A good working model and tight schedule should provide the guidance for all labor- and materials flows in and around the church.

Here, the computer can take a first share of the burden: by digitally scanning facades, the recorded data of the inspection can be linked to a database with all necessary data. Details like materials, state of the material, location, dimensions, sequential number and many other things can be stored for each component in the database.

Read more in Part 2:
Including about the construction of a Gothic church, logistical bottlenecks, professionals and more…