What causes cracks ?
The causes of cracks are many and varied, and it’s worth knowing the main ones to understand them better.
A few explanations about cracks and their origins
Cracks are the most common manifestation of disorders affecting buildings: exterior and interior walls, facades, partitions, floors, cladding, tiles, paving, etc.
Causes of cracks in walls
Cracks in a building can have various causes, and it is often necessary to identify the source of the problem in order to carry out the appropriate repairs. Without being exhaustive, here are some of the common causes of cracks in buildings:
Shrink-swell of clay soils
Clay soils contract and expand according to their water content. Alternating rain and drought can cause significant variations in the soil beneath the building, leading to differential movement and cracking. This effect can be amplified by the presence of vegetation near the building, which tends to absorb water during periods of drought, accentuating the shrinkage effect.
Soil subsidence
This phenomenon can be of natural origin or triggered by human activities such as mining or construction work (building foundations, drilling, etc.). Alterations to the soil structure resulting from these activities can lead to subsidence, causing cracks to appear in nearby buildings.
Foundation problems
Whether due to inadequate design, poor quality building materials or inappropriate construction methods, foundation problems can be the cause of cracks in walls. Faulty foundations can lead to settling, cracking or deformation, putting stress on the building structure.
Ground vibrations and movements
Cracks in buildings can be triggered by a variety of factors, such as seismic vibrations, nearby human activities such as construction, or intensive road traffic.
Seismic vibrations, often linked to tectonic activity, exert pressure on foundations, increasing the risk of cracking. Similarly, nearby construction and road traffic generate ground movements which, over time, can weaken structures.
Temperature variations
Temperature variations, particularly freeze-thaw cycles, are a major cause of cracks in buildings. These thermal variations create stresses on building materials and foundations, causing repeated expansion and contraction.
Frost can be particularly damaging, generating pressure on the structure, especially if water has infiltrated stones, bricks, joints, etc. Ground frost can also be a source of heave movements, especially if certain factors are combined (e.g. clay soils), and can destabilize the building and create cracks.
Construction faults
Cracks in structures can be caused by construction faults, due to errors in design or workmanship. Poorly executed joints, inadequate structural reinforcement or defects in materials can weaken a building’s stability. Inappropriate joints allow water to infiltrate, causing damage and cracks in buildings.
It is important to call in construction/building experts to assess the cause of cracks and determine the best approach to repairing them sustainably.
In some cases, foundation repair, drainage or waterproofing work may be required to resolve the problem at source. Cracking is a complex subject, with so many causes that it is important to diagnose the origin before carrying out effective repairs.
Why measure the evolution of a crack?
Before prescribing any treatment, you need to ask yourself some fundamental questions: is the crack dead or alive? Is it evolving? When and by how much?
A phenomenon can only be properly analysed if it can be expressed in figures.
Thanks to the measurement, it is possible to determine whether the crack is still alive and therefore to act accordingly. We offer a complete range of gauges for monitoring cracks. The technical data sheet explains how to choose the right crack monitor for the crack/movement to be measured.
How long should a crack be observed?
There is no single rule, because the answer depends on the context and the cause of the disorder.
In all cases, it is a good idea to take measurements very regularly at the outset, and to space them out as you go along if no movement is observed.
In the case of cracks linked to soil movement, as a general rule, it is recommended that the gauges are left in place for a year to check whether the changing seasons have an effect on the movement of the cracks.
A minimum of 4 readings per year should therefore be taken. As far as the number of readings is concerned, although 4 is a minimum, there’s obviously nothing to stop you doing more, especially if you notice significant variations.
In specific cases and where there is any doubt, it is advisable to consult a building expert, who will be able to refine and adapt the readings to suit the context.
How do you know whether the crack is dead or alive?
The definition of a dead crack (i.e. one that is no longer active) is one 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 for a crack to be considered dead is one year. And although this is not an absolute rule, it is customary to consider that after 3/10 to 5/10 mm of movement the crack is not dead.
To interpret the results of your measurements, we can only advise you to contact a building expert who will be able to give you the reason for the damage, whether it is active or not and, if necessary, the solutions to be implemented.