Explanations about cracks

Where do cracks come from?

Cracks are the most common manifestation of disorders affecting the building: exterior and interior walls, facades, partitions, floors, coverings, tiles, paving…

Cracks correspond to linear openings with a more or less regular pattern, whose width is between 0.2 and 2mm. Below 0.2mm, they are micro-cracks. Above 2mm, they are cracks.

Whatever their size, only a building expert will be able to identify the origin of the cracks, which can be multiple and varied: the nature of the building materials themselves, desiccation shrinkage, foundation movements, soil shrinkage and swelling, creep under load, movement following an earthquake, the effect of wind, etc.

Cracking is a complex subject, the causes are so numerous that it is important to diagnose the origin before repairing effectively.

Why measure the evolution of a crack?

Before any prescription, it is advisable to ask the fundamental questions: is the crack dead or alive? Is it evolving? When and by how much?

A phenomenon can only be correctly analysed if it can be expressed in figures.

It is to answer this question that we offer a range of products specifically designed to monitor cracks. Accurate to 1/10th of a millimetre up to 1/50th, reliable and easy to install, they allow the precise measurement of the opening of cracks and their other variations.

Thanks to the measurement, it is possible to determine whether the crack is still alive and therefore to act accordingly.

Which instrument should be used to measure the evolution of a crack?

For each type of crack or deformation there is a Saugnac gauge to carry out the measurement. The most traditional products are those that measure the crack evolution on one axis.

For more specific cracks or deformations, you can consult our guide to help you choose the right product. And we remain at your disposal to answer your questions.

En cas de fissure ou déformation plus spécifique vous pouvez consulter notre guide d’aide au choix. Et nous restons à votre disposition pour répondre à vos questions.

How long should I monitor?

There is no single rule as the answer depends on the context and the cause of the disorder.

In all cases, it is wise to carry out measurements very regularly at the beginning and to space them out as time goes by if no movement is observed.

In the case of cracks related to soil movement, as a general rule, it is recommended to leave the gauges in place for a period of one year in order to check whether the alternation of the seasons has an impact on the movement of the cracks.
Therefore, a minimum of 4 readings per year should be taken. Concerning the number of surveys, if 4 is a minimum, there is obviously nothing to prevent you from doing more, especially if you notice significant variations.

For specific cases and in case of doubts, it is advisable to contact a building expert who will be able to refine and adapt the surveys according to the context.

How do you know if the crack is dead or alive?

The definition of a dead crack (i.e. one that is no longer active) is a crack whose opening no longer varies over time, whatever the temperature or stress conditions of the structure.

Still in the case of soil movement, the minimum duration to consider that a crack is dead is one year. And without this being an absolute rule, it is usual to consider that beyond 3/10 to 5/10 mm of movement the crack is not dead.

For the interpretation of the results of your readings we can only advise you to approach an expert who will be able to give you the reason for the disorders, their active character or not and if necessary, the solutions to be implemented.