Cracks Reappeared After the Heatwave: What to Do in the Alpes-Maritimes and Var
Every summer, after a period of intense heat and prolonged drought, many property owners along the Mediterranean coast notice cracks they thought had stabilised opening up again, or new fissures appearing on their facades. This phenomenon is far from trivial: it stems from a well-identified geotechnical mechanism known as clay shrink-swell, commonly referred to by its French acronym RGA. Understanding this cycle is essential to know when to call in an expert and how to properly document the situation for a potential insurance claim.
Why cracks open up precisely during a heatwave
The clay-rich soil found in many areas of the Alpes-Maritimes and Var behaves like a sponge in response to changes in moisture. When properly hydrated, it maintains a stable volume that provides even support to foundations. But during a heatwave, intense evaporation dries out the topsoil, causing the clay to shrink. This shrinkage is not uniform across a building: it depends on sun exposure, the presence of nearby vegetation drawing water from the soil, and the depth of the foundations at each point.
The result is differential settlement: some parts of the building sink slightly more than others, generating mechanical stress within the structure. This stress shows up as cracks, most often diagonal, located at the corners of openings, at the junctions between an extension and the main building, or at other structural weak points. When autumn rains return, the soil swells back up, and some cracks may partially close, giving the misleading impression that the problem has resolved itself.
A cycle that worsens with each repetition
It is precisely this cyclical nature that makes the phenomenon dangerous for a building’s structure over the long term. Each shrink-swell cycle places renewed stress on materials already weakened by previous episodes. A crack that appears to close in winter has not necessarily healed: the internal micro-damage to the masonry or concrete persists, and the crack is very likely to reopen, often wider, during the next drought. With climate change and the increasing frequency of intense heatwaves on the Côte d’Azur and in the Var, this phenomenon has been accelerating in recent years.
The right time to call in an expert
Contrary to popular belief, it is not necessarily best to wait until winter to have cracks that appeared in summer assessed. The most informative time for a diagnosis is actually during or just after the drought episode, when the cracks are at their widest and most representative of the true extent of the phenomenon. An expert intervening at this point can set reference markers, install a crack gauge, and thus document the maximum amplitude of the movement.
Ideally, monitoring over several months, or even several seasonal cycles, makes it possible to objectively determine whether the damage is active or stabilised. This data determines both the nature of any necessary repair work and the strength of an insurance file in the event of a drought-related natural disaster claim.
How to properly document a worsening crack
Even before an expert intervenes, a few good habits help preserve useful evidence. Photographing each crack with a ruler or reference object to show scale, and noting the date of the photo, provides a first usable record. It is also useful to mark the visible ends of the crack in pencil, so that any progression can be visually confirmed at the next observation.
However, these visual records, while useful, remain insufficient to build a solid technical file. This is where instrumented expertise comes in: Frédéric, a specialist expert at Cassini Expertise, uses a Trotec crack gauge to precisely measure the opening and evolution of cracks to within a tenth of a millimetre. This measurement, combined with a thermal camera to detect any associated water infiltration, and a moisture meter to rule out other causes of dampness, provides a reliable technical data set.
Surface crack or structural damage: an essential distinction
Not all cracks that appear after a heatwave are equally serious. A fine crack, less than two millimetres wide, located on a facade render without passing through the masonry, is most often a superficial crack linked to the building’s normal movement. On the other hand, a through-crack, visible both inside and outside the building, showing an offset or a step between the two edges, or accompanied by other issues such as sticking doors or cracked tiling, should raise concern about possible structural damage linked to the soil.
Only an on-site diagnosis, carried out by an experienced professional equipped with the right instruments, can reliably distinguish between these two situations and determine the next steps: simple monitoring, an insurance claim, or a further geotechnical study.
An independent diagnosis, with no work to sell
Cassini Expertise has no commercial ties with underpinning or resin injection companies. This independence ensures that the diagnosis of your cracks reflects only the technical reality observed, with no incentive to steer you towards costly and sometimes unnecessary work. The expert report provides an objective basis, usable both for simple monitoring and, where applicable, for a drought-related natural disaster insurance claim.
A free quote is provided after an initial discussion to understand the property’s location, in the Alpes-Maritimes, Var or Bouches-du-Rhône, as well as the nature of the damage observed.
Frequently asked questions
My cracks close up in winter, should I still be worried?
Yes, a crack that partially closes in winter is not repaired for all that. The internal micro-damage persists, and the crack is very likely to reopen, often wider, during the next drought period.
Should I wait until autumn to have my cracks assessed?
No, quite the opposite: it is best to call in an expert during or just after the drought episode, when the cracks are at their widest and therefore most representative of the phenomenon.
How can I tell if a crack is superficial or structural?
A fine crack, less than two millimetres wide, on render without passing through the masonry, is most often superficial. A through-crack, with an offset between the edges, combined with other issues such as sticking doors, requires a thorough diagnosis.
Is crack gauge monitoring really necessary?
A crack gauge allows the evolution of a crack to be measured objectively over time, to within a tenth of a millimetre. This data is crucial to establishing whether the phenomenon is active and to strengthening an insurance file in the event of a drought-related claim.
For a free quote and a diagnosis of your cracks in the Alpes-Maritimes, Var or Bouches-du-Rhône, contact Cassini Expertise on 04 22 46 06 04 or by email at [email protected].
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