French President Macron is committed to Notre Dame to be built in five years. But first the extent of the damage must be found, says wood expert Thomas Eißing in the DW-Interview.
DW: the President of France, Macron speaks of five years, to Notre building Dame. They believe that this period of time is realistic?
Prof. Thomas Eißing: When it comes only to the pure roof structures, are five years, in my eyes, a realistic span of time. For the recovery of the internal structure and the masonry, must ersst be a thorough damage survey.
The roof made of wood is completely burned. What are the cultural and historical significance he had for Notre Dame?
Because they actually used the all-important question. The development of the French Gothic style in the 13th century. Century type bound to the Cathedral-and thus also a special roof developed form, namely, the equal-sided built-up roof triangle. The roofs were steeper, and now had to be against wind forces better braced. Therefore, the constructions were more complex.
Firefighters and structural engineers inspect the damage to the building
The roof trusses of the Romanesque period had a significantly flatter roof pitch and could be easier constructed. The special feature is that the Cathedral-Gothic style, the rooms of people in France, a first flowering time have experienced, which was exemplary for the whole of Europe.
The leaders in this time. You have the early, so-called hanging works of ornamentation. This roof over the side aisles and the choir of Notre-Dame from the 13th century. Century is therefore of great importance.
Must be because of the complete roof to be demolished in the Wake of the reconstruction – or you can build on it again?
There’s a lot that seem to be crashes. However, I would try to recover better preserved parts, because the historical connection techniques are of importance.
In the case of the wood of the roof is of oak, and in General, oak charred in the outer layers only, and not burn out completely. Actually, the wood structures often bare-bones.
The remaining parts of the wooden construction of the roof are heavily charred
This is not in Paris, the case is likely to be on Conjunction with the lead coverage of the roof. Lead has such a huge heat storage capacity, which fires the fire again and again. This combination of wood and lead, was probably the reason that it came to a devastating fire.
The wood should also be obtained. France still has many oak forests in the own country and the quantities are not so exorbitant. The roof has a span of 13 or 14 meters according to you need a 13-metre-long rafters. You can find it.
You are an expert on wood, but can you tell something about the condition of the stones? You can use the still?
Stone, heated, loses its strength. There must now be a damage survey, to see which need to be replaced.
Aerial view of the destroyed roof structure of Notre Dame
The Cologne Cathedral, which was destroyed in the Second world war, then a roof made of steel. Something like that in Paris would also be conceivable? Or would that make the character of the Church, so to speak, broken?
The Problem is that steel is much more critical in a fire. Wood in itself is not so easily combustible. A great bar from 20 to 20 inches of oak wood would form in the event of a fire first, a carbonization layer and a sheath made of charred wood acts as an insulating layer. Wood burning only at a temperature of 200 to 275 degrees. The wood components are decomposed by the heat, and into the gas phase.
If the temperature inside the beam increases over 200 – 250 degrees, pyrolysieren the wood, that is not in the gaseous state transgressed and will not burn. Therefore, also the charred wooden skeleton remains of a house after a fire.
Steel loses in the event of fire, its strength and would collapse. Steel must therefore be covered or with the appropriate fire protection be provided.
Would you recommend that you build the roof from wood?
I would at least stimulate a discussion. Usually complete reconstructions are to be avoided in historic preservation. The authenticity of historic buildings is of crucial importance. In the case of Notre Dame, the original is lost in the substance of the roof plant. On the other hand, it is so that we have at the Cathedral, a very unique design in front of us.
Reconstructed: The Cologne Cathedral and got to the 2. World war a new roof
I therefore think it is appropriate to reflect the original roof in Parts to restore to the importance for the construction and craft making history come alive. And to show how the original once looked like. There are still many craftsmen who master the ancient connection techniques, and this would certainly fix it.
Are there any experts who know this area so well that you can set as the master builders of the Gothic cathedrals – Notre-Dame of appropriate maintenance?
A prerequisite is that there are blueprints, which is not the case. The Roof was already in the 1930s, in Parts up to measure. There is also a model of the roof of Henri Deneux from this time. That is, it has a pretty good template of the node.
The old techniques are manageable and if you get the appropriate oak, which is, in my eyes, the roof chair with good planning actually to reconstruct it.
Such a reconstruction is more difficult when old structures exists and the old and new buildings need to be merged?
It is a decision, in principle, to reconstruct the historic roof, or you don’t want to put on a modern roof, because it is not directly visible. But often, groups of visitors are guided by the roof works, as a part of the tourism program.
Cathedral of Notre Dame in Paris in front of the fire
The question can be answered with Yes or no. I would suggest, a part of the historical design section to reconstruct and combine with a modern design. Something to think about and you should discuss. I’m sure that the heritage authority will come in France to make a reasonable decision.
It should be 800 million euros in donations has been pledged for the reconstruction of Notre-Dame. The Dresdner Frauenkirche, which has been, by comparison, 182 million euros. You can compare both projects with each other?
This is an interesting question you ask. The actual amount of the cost I can not judge. It is crucial now that the damage is found. How sustainable is the wall crowns? How much of the fire has attacked the vault and the buttresses?
If you build a Church like the Frauenkirche from scratch, this is much easier, because you can calculate from the outset the risks and costs. In Dresden, a new building has emerged, albeit in the guise of the Old.
In the case of Notre-Dame it is a little different: the Church in The stone is preserved, thank God, with the still open question of how strong the damage is in the Detail. The damage survey will take certainly a half to three-quarters of a year, until it is accurately measured and mapped.
Therefore, it is still too early to talk about the stone, but on the roof you can say that The reconstruction should be no Problem.
The interview was conducted by Sabine Oelze
Prof. Dr. Thomas Eißing, wood is host to the Institute for care of monuments, University of Bamberg. His book “Church roofs in Thuringia and southern Saxony-Anhalt” is a standard work for the churches in Central Germany.