Why the roofs of Paris are made of zinc ?

Why the roofs of Paris are made of zinc ?

[R. Baltus Eng-Architect – VMH Association President]

When something is unanimously appreciated and recognised, it is rare and some time undelicate that one ask why ?

Obviuously, there were no reason for such a sharp transition between the aspect of a medieval old city that Paris was at the end of the 18th century, and the Haussmannian style it adopted 50 years later !

From high pitched terra cotta tiles roofs built on heavy wood frameworks to the gray zinc panels installed on light weighted mansard shaped attics, who should have imagined such a revolution ?

The success of rolled zinc as a building material and its prevalence in the region of Paris is due to the exceptional conjunction of historical events, technological progress, installation techniques as well as social and political choices that have mainly occurred during the first half of the 19th Century”

What will follow, is just a summary of those events. For the specialists, I’ll take the time later on to go more into details….

1. Technological breakthrough

It took a pioneer in Liège (The chemist-abbot Jean Jacques Dony) and the invention of his very innovative process of reducing zinc ores to obtain pure zinc, then the filing of a patent and the development of the industrial process to produce it on a large scale.

It took a nearby and exceptionally well-endowed mine, the Altenberg mine (translate in the french Vieille Montagne) to ensure the constant supply of his plants

2. Politics and History

It took an emperor. Yes, because this adventure began in a German-speaking country far from Paris on the borders of the First Empire. Napoleon, by agreeing to give up the concession for this mine, gave the initial impetus. After the Treaty of Versailles, the rich mine, failing agreement, became the center of gravity of a politically neutral micro-territory between the kingdoms of Prussia and the Netherlands. It will remain independant, for a century, managed under Napoleonic law!

It was because he lived under Napoleon that the new Brussels owner of the Vieille Montagne company , François-Dominique Mosselman, had also invested in Paris by forging links with the French financial and political worlds as from the beginning of the 19th century

Therefore zinc came straight to Paris from the Altenberg Mine via the St Leonard plant in Liège! This lasted until 1884 when the mine was declared empty. In the meantime the Vieille Montagne administrators had found many other mines to exploit. But this is another story!

3. Town planning, demography, architecture, health care and safety

It took also the industrial revolution.

History shows that, like other European capitals, Paris has experienced rapid population growth commensurate with the effects of the fast changes industry brought on populations. The industry is beginning to attract future workers from rural areas to the big cities. The intensification of their movements with that of raw materials and the urgent need for housing will accelerate the transformation of the streets and consciences.

Hygienist concerns and competition, particularly with London, will also influence planning choices. Napoleon wanted great avenues to connect the great monuments, his successors also wanted to clean up, raze the slums, remove the narrow streets, reduce the risk of fire. They will therefore call on recognized architects and town planners and entrust the implementation of their plans and recommendations to zealous prefects.

Although they were influenced by the centralism of politics, in the 1820s those town-planners and prefects, were to enact rules of gold that would mark the city for a long time. They will define a style for the façades based on a simple hierarchy between the floors according to their use, they will impose noble materials, they will mainly create templates for the buildings and rules of proportions between the width of the roads (narrow streets, streets, avenues, boulevards) and the height of the buildings up to the cornice and impose the recess portion of the roofs

This last point is important because the cornice is the starting point of the roof. Reduce the visible impact of the roof from the street is the objective. Under the old roof, nothing happens, it is a tile holder, a massive uninhabitable framework on the equivalent of several floors. The mansard-type of attic created a century ago is thus given pride of place. With its almost vertical breeze and then lower slope terracing, it saves timber. Less weighty due to its shape it also saves on the top floor walls.

If the mansard frame should theoretically fit in a perfect arc of circle between the cornices, it is to allow the use of traditional materials in small elements (flat tiles or slates). Zinc will completely change the game. Much lighter than all other materials including lead, and just as durable, it is offered in long stapled plates that fit efficiently on very low slopes. Here is “The” solution to lower the slope of the terraces, reduce the weight of the frames and make the attic usable as storage places or rooms for the small staff !

These advantages will very quickly come to the ears and portfolios of investors who will favor this zinc recently available in sufficient quality and quantity and at competitive prices. They will impose it !

4. History and short story of the zinc gutter

We have seen that zinc has gained its own braid of material from the roofs of Paris thanks to its own qualities. It still took a few nudges to accelerate the process.

We all know that the ancient cobbled streets of Paris were designed as vast channels to ensure the rapid flow of rainwater. These coming straight from the roofs tended in high wind to be folded down on the façades and to damage the lime plaster. It is said that the decision of Prefect Haussmann to impose on the buildings on the street the collection of rainwater at the level of the cornice, was blown to him by the Duke of Morny, half-brother of Napoleon III and famous lover of Fanny Mosselman, co-owner of the Vieille Montagne company !

No other material of the time could respond as well to this need so obvious not only in Paris but throughout the country. This simple decision will sharply accelerate the development of the zinc gutters and downpipes and consequently the exponential development of the Vieille Montagne company !

5 . Installation techniques and zinc roofers’ competence

It is worth recalling that zinc material in its laminated form is at the origin of a profession, that of « Zingueur » in french (zinc roofer or tinsmith in the UK) and their competence which is summarized in the word « Zinguerie » in french or zinc works in english (*)

This skill is not the result of chance, nor of an ancestral tradition handed down from generation to generation by high skilled masters-roofers since Antiquity. No, zinc is a new material, which comes between copper and lead to change the game. Its characteristics are so special, including its very low melting point which allows soldering, that it is necessary to educate the users.

This is what the Vieille Montagne will do by publishing, from the outset, implementation guides, detailed sketches to train the zinc workers, argumentaries, drawings and views of works to inspire architects and builders.

Thus, in about thirty years, between 1820 and 1850, the principles of assembly, covering, expansion or fixing of roofing panels in folded elements known as roll cap system will be enacted, tested and validated. These principles and their regional variants are still in use and taught in schools for zinc roofers .

In the middle of the 19th century, zinc became a must not only in Paris but also in the regions of the Pays de Loire or in the great West where natural slate dominates. Zinc becomes the product of the roof seams which guarantees for a long time the sealing of connections of all types between materials. It is ready to cover the Paris of the prefect Georges Eugène Haussmann

(*) see in this connection the collective work: “Les 101 mots de la Zinguerie” Editions Archibooks Paris 2016

7. A strong marketing policy

The success of the Vieille Montagne is certainly due to the tireless efforts of its engineers to improve the initial refining process in order to increase its efficiency

It is also due to the undeniable quality of its leaders who have discovered and exploited new mines, filed numerous patents, formed international alliances and considered new uses for the new material

But below that, there is the great capacity of these leaders to make their projects and materials known to the outside world. Indeed, they understood from the outset that communication would be a key element of success. This strategy around the brand and the initials VM has been a very consistent work. With today’s eyes and practices, we can marvel at the worldwide success of an Vieille Montagne brand with a French name and a little outdated, which English-speaking customers respectfully called “Billy Mountain” or Germans who spoke of the “Viel Montag”

One only has to look at how in 1868, at the very beginning of photography, the administrator Alexandre St Paul de Sinçay, used a photographer to immortalize the staff of his factories, executives and workers imitating in the studio with their real tools in front of the camera their various trades or also used a famous watercolor painter to represent all the sites of the company from 1851 and to distribute them in luxurious albumsLa Vieille Montagne, through its sales teams, published technical documents very early and very regularly, quickly becoming professional bibles, as the details and recommendations were enlightening to users. These catalogs and guides with sketches or views of realisations have marked generations of roofers and tinsmiths. They are always wanted!

And what about the systematic participation of the company in the major European exhibitions of the time, from that of London in 1851 with its Crystal Palace to the famous Parisian exhibitions of 1889 and 1900 where more than 75% of the pavilions were covered with zinc!

To make it brief, the success of rolled zinc as a building material and its prevalence in the region of Paris is due to the exceptional conjunction of remarkable inventions, individual initiatives, technological progress, industrial heydays , well-marketed installation techniques, historical events as well as social and political choices that have mainly occurred during the first half of the 19th Century