• More than two weeks after the fatal collapse of two buildings in Lille, the causes of the tragedy are still unknown.

  • Since then, alerts have multiplied about cracks and disorders observed on other buildings in the city center.

  • However, this problem that we seem to be discovering today is far from new.

"We only shed light on these subjects when a tragedy occurs", lamented Mélissa Menet, chief of staff of Martine Aubry, after the collapse of two buildings which cost the life of a 45-year-old doctor, the November 12, in Lille.

Since that day, the city's health inspectors have been inundated with calls and reports of disorders in buildings have multiplied.

Yet there is nothing new under the sun.

The probable causes of the tragedy are perhaps the same that cause cracks in the buildings of Vieux-Lille.

Causes that we seem to discover today but which however do not date from yesterday.



Since the tragedy, hardly a day has gone by without firefighters and city services moving to evacuate buildings after reports of cracks in the facade or in the basement.

Interventions responding to a precautionary principle applied to the letter in the face of a growing movement of concern.

Nevertheless, the pathologies at the origin of these disorders have not appeared recently.

“There are three that are recurrent for Lille, starting with the fact that the city is entirely built on loamy soils without much consistency or lift,” explains Eric Tahon, technical building expert in the Lille metropolis.

A relatively unstable subsoil

"The whole center of Lille is built on the old bed of the Deûle river, filled in, drained, channeled", adds Jean-Yves Mereau, president of the Renaissance association of old Lille.

Beneath our feet, then, is a clay substrate resting on limestone into which oak wood piles have been driven as a foundation to support the buildings.

“For about fifty years, we have built underground car parks, and we pump the water from these car parks to prevent them from being flooded.

Except that it also has the effect of lowering the water table, ”he continues.

A “well-known” phenomenon, to which must be added that of the drought which contracts the clays.

We then obtain a combo whose result is the sinking of buildings.

However, the composition of the subsoil is not the only culprit.

"Since the 20th century, the buildings of Vieux-Lille have been constantly transformed to finally be overused", insists the building expert.

Where a building once housed a single family, it now houses one family per floor, increasing the load factor on the structure accordingly.

“When you get overweight, it's not good for your knees.

It's exactly the same for buildings,” adds Eric Tahon.

Nature does not like a vacuum

The common point between the collapse and the alerts that followed is the presence of shops on the ground floor.

"Fashion, which is also the big problem of Vieux-Lille, is to bring together several houses to make large commercial surfaces by replacing the load-bearing walls with beams", remarks Jean-Yves Mereau.

"These transformations, when they are not done according to the rules of the art, reduce the points of structure and destabilize the buildings", affirms the expert.

The third most common cause of building pathology is lack of maintenance.

Even if the president of Renaissance du Lille ancien admits that the general state of the building in Old Lille is "rather good", he also recognizes shortcomings.

“Collapses of buildings that the owners have left to deteriorate, there have already been some, rue des Arts or even rue du Vieux-Faubourg”, he recalls.

“The owners do not do the work or do it badly.

Sometimes lack of means, especially for small condominiums.

It even happens that we hide the problems behind plasterboard,” laments Eric Tahon.

Does the tragedy in Lille find its origin among these three causes?

Our interlocutors are rightly careful not to advance on this point.

Only the current judicial expertise, as part of the investigation for manslaughter led by the Lille prosecutor's office, will be able to answer this question.

Lille

Lille: Doubt lifted on the threats of collapse for buildings in Old Lille

Miscellaneous facts

Lille: The cracks are getting bigger, three more buildings evacuated for a threat of collapse

  • Lille

  • Hauts-de-France

  • Collapse

  • Building