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New or old, houses that have no cracks are really very rare. Soils move, building materials evolve with the seasons, weather conditions themselves malmèmes foundations and walls. But if some cracks remain superficial, others are dangerous and can compromise the strength of the house. That's why it's important to know how to recognize them.

The characteristics of a dangerous crack

The characteristics of a dangerous crack

Any crack can become dangerous...

A crack is a slit more or less long and more or less wide which assign a wall. Depending on its length and width, a crack is considered benign or dangerous.

  • Microcracks: Filiformes is less than 0.2 mm wide, they remain superficial and a priori do not pose any danger. Nevertheless we must monitor them to be sure that it is not a dangerous structural crack which under the weight of the masonry has closed again...
  • Fine cracks: They are between 0.2 and 2 mm wide. They do not present any danger except, if they evolve and or multiply. This is the sign that they concern the structure of the building (structural crack or crack on the foundations).
  • Dangerous cracks: These are slits more than 2 mm wide and more than 20 cm long.
    They are called through cracks when they cross the wall from side to side. Those are stairway cracks when, they follow the joints of the blocks blocking the wall. And they become infiltrating cracks when water enters the slot.
    Some cracks can reach a few centimeters wide. We then speak of cracks.

The most dangerous cracks...

Depending on their location on the wall or walls, cracks are more or less dangerous and mark disorders that call into question the strength of the structure of the building.
Large horizontal cracks or stairs are often the result of problems in the basement and thus cracks foundations.
Long vertical cracks located at the corner of two walls can cause a uncoupling the walls.
The infiltrating cracks are particularly dangerous because infiltration and the succession of freezing and thawing periods further weaken the wall.

What to do in the presence of dangerous cracks?

When dangerous cracks appear on a wall, you must quickly set up a monitoring and tracking system of their evolution over several months.
There are several ways to measure the extent of cracks:

  • Plaster witness installed astride the edges of the crack.
  • Glass witness included in a plaster sleeve.
  • Graduated or electronic cracker.
  • Extensometer and deformometer.

These measurements make it possible to determine the possible evolution of the cracks and to define their degree of dangerousness.

But it is equally important to determine the causes of their appearance in order to secure and repair the building.

  • Since when did they occur?
  • In which circumstances?
  • What are the aggravating circumstances?

For example, cracks that appeared after a drought while the house is built on clay soil suggest field movements important.
Cracks that have occurred while your municipality is building a building next to your house, this means a problem of weakening your foundations follows a differential settlement.

Alarming signs in the presence of cracks

If the building where you live already has cracks and the following signs appear, react quickly!

  • You hear crunches.
  • New cracks appear on the exterior and / or interior walls.
  • The existing cracks widen and deepen.
  • Water infiltration and significant moisture problems.
  • The condition of the building is deteriorating: Crushed falling, tile or slab moving, etc.


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