Six-Fours-les-Plages: Clay Soil, Subsidence and Cracks – Official Data

The geological and climatic context of Six-Fours-les-Plages

Six-Fours-les-Plages, with the hills of Gros Cerveau and Mont Caume as its backdrop and its coastal plain facing the Mediterranean, has a contrasting topography that weighs heavily on the defects we encounter on the ground. The built fabric is highly heterogeneous: Provençal villas from the 70s-80s built on shallow foundations, more recent houses from the estates that multiplied under Var property pressure, and a few modern residences on the outskirts. The clay soil, typical of this part of the Var, is particularly sensitive to the shrink-swell phenomenon: during prolonged summer drought the clay contracts, then swells again with the autumn rains, generating differential settlement under the foundations, especially where these were not designed on the basis of a proper G2 soil study. Vegetation also plays a significant role: the pines and olive trees planted too close to the houses, very common in the commune’s gardens, pump moisture from the soil at depth and locally intensify this drying-out of the clay, creating zones of cracking around façade corners and slab-to-wall junctions. Houses built on a slope, on the flanks of the hills, additionally face lateral earth pressure that further weakens the footings. It is this combination of clay soil, ageing unreinforced buildings and tree cover that explains the frequency of the cracks we record in Six-Fours-les-Plages.

Drought in the rear-view mirror: 35 years of measured rainfall

The area’s weather archives cover 35 complete years (1991-2025). The driest ever recorded: 2007, with 400 mm over the year, against a local average of 695 mm. 2022 ranks as the 12th driest year out of 35 (559 mm against an average of 695 mm); 2023 follows in 13th place (577 mm).

This ranking gives the true measure of the recent sequence: when the years 2020-2023 sit high up the list of dry years, the clay has had no time to rehydrate between episodes – the textbook scenario for delayed cracking. The reverse is just as instructive: a very wet year following an exceptional drought triggers abrupt swelling of the ground.

Damp, water ingress and rising damp in Six-Fours-les-Plages

Damp in a wall can have four causes – rising damp, water ingress, condensation or a leak – and the treatments are completely different depending on the origin.

You have noticed damp marks in your home in Six-Fours-les-Plages, and you may already have read online that it needs resin injections or a mechanical ventilation system. My message: not so fast. Without a diagnosis, treatment is guesswork – and in half of cases the wrong treatment solves nothing.

The 4 causes and how to recognise them

• Rising damp: low stains, halos at the foot of the wall, efflorescent salts, deterioration of the renders over the first 50 to 80 centimetres. Typical of older houses with no damp-proof course, common in the old quarters of Six-Fours.
• Water ingress: rain-related stains, appearing near a roof, a terrace or a poorly waterproofed façade, often worse in winter.
• Condensation: mist on cold surfaces, mould in room corners or around windows, linked to poor ventilation rather than to water from the ground.
• Leak: a localised, evolving stain, sometimes accompanied by excess water consumption, often on a chased-in pipe or a buried run.

The trap of the diagnosis sold by the treatment contractor

Many injection companies offer a “free quote” before selling you their treatment. The problem: they are paid on the sale of works, not on the accuracy of the diagnosis. The result: resin injections are often proposed when the problem is water ingress or poor ventilation – a costly, pointless treatment that solves nothing.

Before commissioning works in Six-Fours-les-Plages, have an independent diagnosis drawn up, carried out by an expert with no commercial ties to treatment companies. To understand the mechanisms and good practice in detail, read the damp guide for 06, 83 and 13.

Six-Fours-les-Plages: drought, clay and cracks – what the figures say

Is my cracked house in Six-Fours-les-Plages linked to drought? The GASPAR database records 4 drought prefectoral decrees (full list below) and 8 flood decrees, i.e. 12 natural disaster declarations (Cat Nat) for the commune. Local rainfall confirms the scenario: three deficit years (2020, 2022, 2023), then a rebound to 827 mm in 2024 – exactly the cycle that puts foundations under strain on the cape overlooking the rade (bay).

Cassini Expertise, an independent building expert, handles cracks and drought-related damage in Six-Fours-les-Plages and throughout the Var. This page brings together the commune’s official data to help you work out whether your case is recognised, and what to do next.

Natural disaster declarations (Cat Nat) in Six-Fours-les-Plages: the official record

The GASPAR database (decrees published in the Journal officiel since 1982) records 12 natural disaster declarations (Cat Nat) for the commune:

• 4 drought prefectoral decrees (differential ground movement linked to clay shrink-swell (RGA))
  • event of 01/05/1989 (prefectoral decree of 18/05/1993)
  • event of 01/07/2017 (prefectoral decree of 18/09/2018)
  • event of 01/04/2019 (prefectoral decree of 29/04/2020)
  • event of 01/04/2022 (prefectoral decree of 03/04/2023)
• 8 flood prefectoral decrees and storm

What to do with it: check when your cracks appeared or worsened. If that period matches one of the four drought decrees above, you can file a natural disaster declaration (Cat Nat) claim with your insurer (within 30 days of publication of the relevant decree, or as soon as the link is established by survey). If no period matches, keep your photos and dates anyway: they will serve a claim against the seller in the case of a recent purchase.

The official clay classification (GéoRisques/BRGM)

The GéoRisques platform (BRGM) classifies Six-Fours-les-Plages at high exposure to clay shrink-swell (RGA), with some sectors at medium exposure. This is the level insurers and notaires consult before ruling on a property. Another point to check if you are buying or living here: the commune is at radon potential class 3 (IRSN/GéoRisques data) – request a radon measurement if you have never had one, especially on the ground floor or in a basement.

How to read these two pieces of information together: the clay hazard says what can happen on your plot, the drought decrees say what has already happened in the commune. A high-exposure house that has come through several dry summers carries a risk of damage that is all the better documented – a weighty argument in a survey file or a purchase negotiation.

Six-Fours-les-Plages: 12 Cat Nat prefectoral decrees since 1982, in chronological order

Each line = an event recognised by an interministerial decree published in the Journal officiel (GASPAR database):

• 🔴 05/1989 → 12/1991 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/05/1993)
• 🔴 07/2017 → 12/2017 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/09/2018)
• 🔴 04/2019 → 09/2019 – Drought – clay shrink-swell (RGA) (prefectoral decree of 29/04/2020)
• 🔴 04/2022 → 06/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 4 droughts and 8 floods. Clusters (several decrees close together) flag up crisis periods – the summer of 2022-2023 is the best recent example. An owner whose damage dates from a covered period has a solid Cat Nat file; outside a covered period, the way forward is an action against the seller.

Six-Fours-les-Plages: 12 Cat Nat prefectoral decrees since 1982, in chronological order

Each line = an event recognised by an interministerial decree published in the Journal officiel (GASPAR database):

• 🔵 09/1982 → 09/1982 – Floods (prefectoral decree of 24/12/1982)
• 🔵 08/1983 → 08/1983 – Floods (prefectoral decree of 15/11/1983)
• 🔴 05/1989 → 12/1991 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/05/1993)
• 🔵 09/1993 → 09/1993 – Floods (prefectoral decree of 08/03/1994)
• 🔵 01/1999 → 01/1999 – Floods (prefectoral decree of 23/02/1999)
• 🔵 10/1999 → 10/1999 – Floods (prefectoral decree of 03/03/2000)
• 🔵 10/2012 – Floods (prefectoral decree of 10/01/2013)
• 🔵 09/2014 – Floods (prefectoral decree of 04/12/2014)
• 🔴 07/2017 → 12/2017 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/09/2018)
• 🔴 04/2019 → 09/2019 – Drought – clay shrink-swell (RGA) (prefectoral decree of 29/04/2020)
• 🔵 10/2019 → 10/2019 – Floods (prefectoral decree of 30/10/2019)
• 🔴 04/2022 → 06/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 4 droughts and 8 floods. Clusters (several decrees close together) flag up crisis periods – the summer of 2022-2023 is the best recent example. An owner whose damage dates from a covered period has a solid Cat Nat file; outside a covered period, the way forward is an action against the seller.

The complete chronology of the 12 natural disasters recognised in Six-Fours-les-Plages

Each line = an event recognised by an interministerial decree published in the Journal officiel (GASPAR database):

• 🔵 09/1982 → 09/1982 – Floods (prefectoral decree of 24/12/1982)
• 🔵 08/1983 → 08/1983 – Floods (prefectoral decree of 15/11/1983)
• 🔵 08/1983 → 08/1983 – Floods (prefectoral decree of 15/11/1983)
• 🔴 05/1989 → 12/1991 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/05/1993)
• 🔵 09/1993 → 09/1993 – Floods (prefectoral decree of 08/03/1994)
• 🔵 01/1999 → 01/1999 – Floods (prefectoral decree of 23/02/1999)
• 🔵 10/1999 → 10/1999 – Floods (prefectoral decree of 03/03/2000)
• 🔵 10/2012 – Floods (prefectoral decree of 10/01/2013)
• 🔵 09/2014 – Floods (prefectoral decree of 04/12/2014)
• 🔴 07/2017 → 12/2017 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/09/2018)
• 🔴 04/2019 → 09/2019 – Drought – clay shrink-swell (RGA) (prefectoral decree of 29/04/2020)
• 🔵 10/2019 → 10/2019 – Floods (prefectoral decree of 30/10/2019)
• 🔴 04/2022 → 06/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 4 droughts and 8 floods. Clusters (several decrees close together) flag up crisis periods – the summer of 2022-2023 is the best recent example. An owner whose damage dates from a covered period has a solid Cat Nat file; outside a covered period, the way forward is an action against the seller.

The official exposure to clay shrink-swell (RGA)

The GéoRisques platform (BRGM) classifies Six-Fours-les-Plages at high exposure to clay shrink-swell (RGA), with some sectors at medium exposure. This is the benchmark level used by insurers and notaires to assess the risk on a plot. Worth noting: radon potential class 3 across the commune (IRSN/GéoRisques data) – a health-and-building watch point in the affected zone.

This classification completes the decree history above: the hazard rating says what can happen, the decrees say what has already happened. A house rated “high exposure” that has come through one or more dry summers carries a risk of damage that is all the better documented.

Local rainfall: the trigger for ground movement

Annual rainfall recorded on the Six-Fours-les-Plages weather grid (Open-Meteo data):

• 2019: 877 mm · 2020: 482 mm · 2021: 760 mm · 2022: 559 mm · 2023: 577 mm · 2024: 827 mm
• Average over the period: 680 mm/year, driest year: 2020 (482 mm)
• Three deficit years (2020, 2022, 2023): 482 mm, then 559 mm, then 577 mm
• Rebound in 2024 to 827 mm (+22%)

Shrink-swell plays out in two acts: the drought dries out the clay at depth – this is the shrinkage, and the first cracks appear – then the return of the rain rehydrates the ground abruptly, causing swelling and differential movement. If your house dates from 1970-2000 and rests on shallow foundations, watch it closely: the lag between the dry spell and the appearance of damage is 12 to 24 months, so a crack appearing today may go back to the 2022-2023 drought.

Cracks in Six-Fours-les-Plages: the signs not to neglect

• A stair-step crack, passing through the wall, wider than 2 mm
• A crack that evolves: fit a tell-tale (plaster patch or gauge) and check it monthly for 3 to 6 months
• Associated damage: doors and windows sticking, tiles splitting diagonally, render bulging
• Aggravating factors to check around the house: clay ground, trees near the foundations, failed gutters or drainage

With 4 drought prefectoral decrees recorded in the commune, as soon as two or three of these signals build up at your property, do not repair before having a survey carried out: a simple crack filler without treating the cause will come back within the year. Same reflex if you are about to buy or sell a property showing these signs.

Buying or selling a cracked house in Six-Fours-les-Plages: the legal side

With the recent drought decrees and the volume of transactions underway, many properties are changing hands with damage kept quiet. If you discover cracks after signing, you have two levers:

• Hidden defect (article 1641 of the Code civil): serious cracks, not visible at the viewing, predating the sale → price reduction or cancellation of the sale, action to be brought within 2 years of discovery
• Fraud (dol) (article 1137): the seller knew and concealed the damage → cancellation of the sale and damages, action within 5 years; the commune’s GASPAR decree then backs the file by proving that a recognised episode existed

In both cases, keep all documents (surveys, photos, invoices, exchanges with the seller) and appoint a property-law solicitor (avocat) to launch the proceedings.

How a drought/clay survey unfolds in Six-Fours-les-Plages

Here is what happens in practice when you call us:

• Technical visit: crack survey and classification, crack-width measurements, functional damage
• Context analysis: clay zone, the commune’s natural disaster declaration (Cat Nat) history (4 drought decrees), local drought episodes cross-checked against the appearance of the cracks
• Costing of works: underpinning, injections, drains – with several scenarios depending on your budget
• A written report you can pass to your insurer or your solicitor to support a Cat Nat claim or legal action

Independent expert, with no ties to any building contractor: no repair quote at the end, just a diagnosis. Request a visit in Six-Fours-les-Plages – see also our complete RGA and Cat Nat guide for 06, 83 and 13.

Soil surveys on clay ground: what the regulations say

The requirement for a prior geotechnical survey has applied since 1 October 2020 (ELAN law, art. 68); the new exposure map of 1 July 2026 widens its scope. This obligation, stemming from ELAN law no. 2018-1021, article 68 (decree no. 2019-495 of 22 May 2019), applies particularly to Six-Fours-les-Plages (high exposure in the BRGM classification).

• What it changes for building: the soil survey is no longer an option – the ELAN law makes it compulsory in an exposed zone for every sale of building land and every construction contract. Adapted foundations, ground treatment, drainage arrangements: the specifications flow directly from the survey.
• What it changes when buying a recent property: ask whether the survey was carried out and which specifications were applied. A house built without following the geotechnical recommendations on clay soil is a medium-term cracking risk.
• What it changes when selling: the absence of a survey on a property built before the obligation is not a defect in itself – but if damage appears, a seller who knew about it and concealed it exposes themselves to an action for fraud (dol).
• The link with the data above: Six-Fours-les-Plages combines high exposure with a well-documented history of drought decrees. Building or buying here without checking the nature of the ground means building on a known and measured risk.

Cassini Expertise handles these files: compliance checks between geotechnical specifications and execution, damage surveys on clay ground, counter-expertise. Request a consultation.

Soil surveys on clay ground: what the regulations say

The requirement for a prior geotechnical survey has applied since 1 October 2020 (ELAN law, art. 68); the new exposure map of 1 July 2026 widens its scope. This obligation, stemming from ELAN law no. 2018-1021, article 68 (decree no. 2019-495 of 22 May 2019), applies particularly to Six-Fours-les-Plages (high exposure in the BRGM classification).

• What it changes for building: the soil survey is no longer an option – the ELAN law makes it compulsory in an exposed zone for every sale of building land and every construction contract. Adapted foundations, ground treatment, drainage arrangements: the specifications flow directly from the survey.
• What it changes when buying a recent property: ask whether the survey was carried out and which specifications were applied. A house built without following the geotechnical recommendations on clay soil is a medium-term cracking risk.
• What it changes when selling: the absence of a survey on a property built before the obligation is not a defect in itself – but if damage appears, a seller who knew about it and concealed it exposes themselves to an action for fraud (dol).
• The link with the data above: Six-Fours-les-Plages combines high exposure with a well-documented history of drought decrees. Building or buying here without checking the nature of the ground means building on a known and measured risk.

The soil survey obligation: what has changed since July 2026

Since 1 July 2026, any construction or extension on ground exposed to clay shrink-swell (RGA) requires a prior geotechnical survey. This obligation, stemming from the Climate and Resilience law (article 88), applies particularly to Six-Fours-les-Plages (high exposure in the BRGM classification).

• What it changes for building: the soil survey is no longer an option – it conditions the planning permission. Adapted foundations, ground treatment, drainage arrangements: the specifications flow directly from the survey.
• What it changes when buying a recent property: ask whether the survey was carried out and which specifications were applied. A house built without following the geotechnical recommendations on clay soil is a medium-term cracking risk.
• What it changes when selling: the absence of a survey on a property built before the obligation is not a defect in itself – but if damage appears, a seller who knew about it and concealed it exposes themselves to an action for fraud (dol).
• The link with the data above: Six-Fours-les-Plages combines high exposure with a well-documented history of drought decrees. Building or buying here without checking the nature of the ground means building on a known and measured risk.

Frequently asked questions

Is Six-Fours-les-Plages among the at-risk clay zones?

Yes. The Alpes-Maritimes and the Var are very broadly covered by the clay shrink-swell (RGA) hazard (BRGM mapping, viewable on georisques.gouv.fr). For Six-Fours-les-Plages specifically, the 4 drought decrees recorded in GASPAR show the risk is anything but theoretical: it has already materialised four times since 1989.

Can a cracked house in Six-Fours-les-Plages give rise to Cat Nat compensation?

Only if your damage can be tied to a period covered by a decree (recognised drought periods: 1993, 2018, 2020, 2023) and if the declaration was made within 30 days of publication of the decree. If that deadline has passed or no period matches, the claim against the seller remains – and this is where precisely dating the damage through a survey becomes decisive for your file.

Can the data presented on this page be checked?

Yes: the decrees come from the GASPAR database (Journal officiel, open data sets, 2025 update), the rainfall from Open-Meteo weather archives for the Six-Fours-les-Plages grid. Cassini Expertise does not adjust these figures – you can cross-check them yourself before contacting us.

This week’s drought watch (as at 04/10/2026)

In the commune: recent rain (3 days ago). Rainfall over the last 30 days: 38 mm, against roughly 53 mm expected at this time of year – a 28% deficit.

A sustained deficit over this window, especially in the growing season, often precedes by a few weeks the drop in the water table shown above: it is the first signal owners can track themselves, before any cracks appear.

This week’s drought watch (as at 05/10/2026)

In the commune: recent rain (4 days ago). Rainfall over the last 30 days: 38 mm, against roughly 54 mm expected at this time of year – a 30% deficit.

A sustained deficit over this window, especially in the growing season, often precedes by a few weeks the drop in the water table shown above: it is the first signal owners can track themselves, before any cracks appear.

This week’s drought watch (as at 12/10/2026)

In the commune: recent rain (4 days ago). Rainfall over the last 30 days: 83 mm, against roughly 61 mm expected at this time of year – a 36% surplus.

A sustained deficit over this window, especially in the growing season, often precedes by a few weeks the drop in the water table shown above: it is the first signal owners can track themselves, before any cracks appear.

Where do the rains stand today? (as at 19/10/2026)

In the commune: no significant rain for 11 days. Rainfall over the last 30 days: 83 mm, against roughly 67 mm expected at this time of year – a 24% surplus.

A sustained deficit over this window, especially in the growing season, often precedes by a few weeks the drop in the water table shown above: it is the first signal owners can track themselves, before any cracks appear.

Aquifer memory: 30 years of measurements, a well-documented context

The reference piezometric station for the area (002KZYQ) has been monitoring the aquifer since 1984 – 30 years of records. As at 01/10/2026, the average level over the last thirty days is 103.09 m NGF (French ordnance datum). Across the whole record, the aquifer has spent only 11.3% of its time below this level: a very low level, rarely reached in the station’s history.

• Last equivalent episode: 04/09/2024 – 2.1 years ago
• Frequency: 28 similar episodes recorded since 1984, i.e. an annual return on average – in hydrologists’ language, a rare event
• Historic minimum: 102.04 m NGF, reached on 30/10/2022

This long memory changes how the risk is read: a low level is not just a weather episode, it is an event whose frequency is known. For a house on clay, it is this frequency that tells you the probability of fresh settlement – and therefore how urgent the precautions are.

Survey carried out by Frédéric Faucouneau, independent building expert – Antibes, Alpes-Maritimes (06), Var (83), Bouches-du-Rhône (13). Find out more

📅 Last updated 24/10/2026 - Cassini Expertise, independent building expert – departments 06, 83 and 13.