La Crau: Clay Soil, Subsidence and Cracks – Official Data

La Crau facing shrink-swell: what to do when the figures concern you?

La Crau combines a clearly identified clay soil and a substantial Cat Nat record: the GASPAR database records 2 drought prefectoral decrees (full list below) and 8 flood decrees, i.e. 10 in total. Local rainfall matches the classic clay shrink-swell (RGA) scenario: two dry years (2020, 2022), then a rebound to 898 mm in 2024 – exactly the shrink-swell cycle that weakens foundations in the alluvial plain of the Gapeau. If your house has cracks and stands in this area, the sections below tell you what to check, when to worry, and who to call.

Cassini Expertise, an independent firm, works in La Crau and throughout the Var diagnosing cracks and drought-related damage. This page brings together the official data specific to the commune, with no commercial additions – keep it to hand if you need to support an insurance file or a purchase negotiation.

Can my cracked house in La Crau be compensated under a natural disaster declaration (Cat Nat)?

The GASPAR database (decrees published in the Journal officiel since 1982) records 10 natural disaster declarations (Cat Nat) for the commune:

• 2 drought prefectoral decrees (differential ground movement due to clay shrink-swell (RGA))
  • event of 01/07/2017 (prefectoral decree of 18/09/2018)
  • event of 01/04/2022 (prefectoral decree of 03/04/2023)
• 8 flood prefectoral decrees and storm

What to do in practice: pin down the date your cracks appeared. If it falls within one of these two windows (2017 or 2022), you can claim natural disaster declaration (Cat Nat) compensation – provided you declared the loss to your insurer within 30 days of the decree. If that deadline has passed, or the damage predates the purchase, the route of a hidden defect (vice caché) or fraud (dol) claim against the seller remains (see below). In both cases, keep your dated photos and your invoices.

Is La Crau in an at-risk clay zone? What GéoRisques says

The GéoRisques platform (BRGM) classifies La Crau at high exposure to clay shrink-swell (RGA), with some sectors at medium exposure. This is the benchmark level your insurer and your notaire already look at to assess the risk on your plot – better to check it yourself before they do, on georisques.gouv.fr, by entering your address. Also worth noting: radon potential class 3 across the commune (IRSN/GéoRisques data) – a point to watch if you have a basement or a poorly ventilated crawl space.

This classification completes the decree history above: the hazard rating says what can happen, the decrees say what has already happened. If your house is rated “high exposure” and has come through one or more dry summers, the risk of damage is no longer a hypothesis – it is documented.

Why does my house crack after the drought, and not during it?

Annual rainfall recorded on the La Crau weather grid (Open-Meteo source):

• 2019: 867 mm · 2020: 475 mm · 2021: 753 mm · 2022: 578 mm · 2023: 611 mm · 2024: 898 mm
• Average over the period: 697 mm/year, driest year: 2020 (475 mm)
• Two clearly dry years: 475 mm in 2020, 578 mm in 2022
• Then a clear catch-up in 2024, at 898 mm (+29%)

The phenomenon plays out in two stages. First the drought dries out the clay at depth: it shrinks, the first cracks appear. Then the rain returns and abruptly rehydrates the soil, which in turn swells – and it is this differential movement that damages the structures. If you live in a 1970-2000 villa on shallow foundations, yours is the house that takes the strain first: expect a 12 to 24-month lag between a dry summer and the appearance of cracks. In other words, if your walls are cracking today, think back to the summer of a year or two ago, not to this week’s weather.

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

In the commune: recent rain (3 days ago). Rainfall over the last 30 days: 31 mm, against roughly 51 mm expected at this time of year – a 39% 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.

Drought right now (as at 05/10/2026)

In the commune: recent rain (4 days ago). Rainfall over the last 30 days: 31 mm, against roughly 52 mm expected at this time of year – a 40% 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.

Drought right now (as at 12/10/2026)

In the commune: recent rain (4 days ago). Rainfall over the last 30 days: 107 mm, against roughly 61 mm expected at this time of year – a 75% 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.

Drought right now (as at 19/10/2026)

In the commune: recent rain (1 day ago). Rainfall over the last 30 days: 119 mm, against roughly 70 mm expected at this time of year – a 70% 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.

When was the aquifer last this low?

The reference piezometric station for the area (002LDFT) has been monitoring the aquifer since 2000 – 26 years of records. As at 02/10/2026, the average level over the last thirty days is 141.35 m NGF (French ordnance datum). Across the whole record, the aquifer has spent only 7.2% of its time below this level: a very low level, rarely reached in the station’s history.

• Last equivalent episode: 04/01/2024 – 2.7 years ago
• Frequency: 26 similar episodes recorded since 2000, i.e. an annual return on average – in hydrologists’ language, a rare event
• Historic minimum: 141.1 m NGF, reached on 01/10/2000

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.

La Crau: 10 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):

• 🔴 07/2017 → 09/2017 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/09/2018)
• 🔴 04/2022 → 09/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 2 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.

La Crau: 10 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)
• 🔵 10/1988 → 10/1988 – Floods (prefectoral decree of 22/02/1989)
• 🔵 01/1999 → 01/1999 – Floods (prefectoral decree of 23/02/1999)
• 🔵 01/2014 → 01/2014 – Floods (prefectoral decree of 27/02/2014)
• 🔵 09/2014 – Floods (prefectoral decree of 04/12/2014)
• 🔵 11/2014 → 11/2014 – Floods (prefectoral decree of 27/04/2015)
• 🔵 12/2014 → 12/2014 – Floods (prefectoral decree of 03/03/2015)
• 🔴 07/2017 → 09/2017 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/09/2018)
• 🔵 11/2019 → 11/2019 – Floods (prefectoral decree of 28/11/2019)
• 🔴 04/2022 → 09/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 2 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 10 natural disasters recognised in La Crau

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)
• 🔵 10/1988 → 10/1988 – Floods (prefectoral decree of 22/02/1989)
• 🔵 01/1999 → 01/1999 – Floods (prefectoral decree of 23/02/1999)
• 🔵 01/2014 → 01/2014 – Floods (prefectoral decree of 27/02/2014)
• 🔵 09/2014 – Floods (prefectoral decree of 04/12/2014)
• 🔵 11/2014 → 11/2014 – Floods (prefectoral decree of 27/04/2015)
• 🔵 12/2014 → 12/2014 – Floods (prefectoral decree of 03/03/2015)
• 🔴 07/2017 → 09/2017 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/09/2018)
• 🔵 11/2019 → 11/2019 – Floods (prefectoral decree of 28/11/2019)
• 🔴 04/2022 → 09/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 2 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 clay classification (GéoRisques/BRGM)

The GéoRisques platform (BRGM) classifies La Crau 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.

The official clay classification (GéoRisques/BRGM)

The GéoRisques platform (BRGM) classifies La Crau 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.

What 35 years of local rainfall tell us

The area’s weather archives cover 35 complete years (1991-2025). The driest ever recorded: 2007, with 407 mm over the year, against a local average of 705 mm. 2022 ranks as the 12th driest year out of 35 (578 mm against an average of 705 mm); 2023 follows in 15th place (611 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 La Crau

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 damp marks in your house or flat in La Crau, and a treatment contractor has already offered you resin injections or a mechanical ventilation system? Before signing anything, my advice: wait. A poorly targeted treatment solves nothing and costs dear.

The 4 causes and how to recognise them

• Rising damp: water from the ground rises into the walls by capillary action. Typical sign: halos at the foot of the wall, efflorescent salts, blistering render, often in older houses with no damp-proof course.
• Water ingress: water enters from outside (roof, façade, failed joint, gutter). The marks often appear high up or follow a specific entry point, and worsen after rain.
• Condensation: linked to a ventilation defect. Misted windows, mould in corners, poorly aired bathrooms and kitchens are the first signs.
• Leak: a leaking pipe, drain or buried run. The stain is often localised near a water supply or waste pipe, sometimes accompanied by unexplained excess water consumption.

The trap of the diagnosis sold by the treatment contractor

A company selling resin injections has no interest in diagnosing water ingress or a leak: it will invoice you for an unsuitable treatment that solves nothing, and the damp will return. In La Crau, with its mix of older houses and 70s-80s villas, the four causes are encountered regularly, sometimes combined on the same wall. Only an independent diagnosis, carried out by someone who does not then sell the treatment, identifies the true cause before works are commissioned.

For an independent damp diagnosis in La Crau, contact us. And to understand the diagnostic and treatment methods in detail, read our damp guide for 06, 83 and 13.

What characterises La Crau in building surveys

La Crau, a Var commune of nearly 19,500 inhabitants nestling between the pine- and oak-wooded hills that separate it from Hyères and the agricultural plain facing Toulon, has a building stock particularly exposed to clay-related damage. I work there regularly on 70s-80s villas built on the edge of the relief, often on lightly reinforced shallow foundations, at a time when prior soil surveys were not systematic. The development of many housing estates in the following decades, extending into the plain, took place on heterogeneous clay soils sensitive to the shrink-swell phenomenon: during summer drought, the clay contracts and deprives the foundations of even support, causing differential settlement that translates into façade cracks, often oblique and located at the corners of openings. The proximity of the massif and the slope of the ground further accentuate this phenomenon, because runoff water does not drain away evenly around the homes. Pines planted too close to the walls, heavy water consumers, locally aggravate the drying-out of the soil and multiply the losses we record on individual houses as well as on some more recent constructions – better standardised, admittedly, but sometimes built on backfilled plots without suitable foundation treatment.

Cracks in La Crau: which signs should alert you?

• A stair-step crack, passing through the wall, open by more than 2 mm → to be measured and monitored without delay
• A crack that keeps evolving: fit a tell-tale (band of plaster or gauge) and check it after a few months
• Associated signs not to neglect: doors and windows sticking, tiles splitting diagonally, render blistering and coming away
• Aggravating factors at your property: a house on clay ground, trees near the foundations, drainage that no longer does its job

With 2 drought prefectoral decrees already recorded in the commune, as soon as you build up several of these signs, call in an expert before starting any repair – and above all before any buying or selling decision: rebuilding without a prior diagnosis risks masking the proof you will need for the insurance.

Buying or selling a cracked house in La Crau: what recourse do you have?

Between the recent drought decrees and the volume of transactions underway, properties are changing hands with damage kept quiet. If you are the buyer and discover cracks after the sale, you have two routes:

• Hidden defect (article 1641 of the Code civil): serious cracks, not detectable at the viewing, that appeared before the sale → you can claim a reduction in the price or cancellation of the sale, within 2 years of discovery
• Fraud (dol) (article 1137): the seller knew and said nothing → cancellation and damages, within 5 years; the commune’s GASPAR decree then helps underpin your file

In both cases, the useful first step is to have the damage precisely dated by an independent expert, before contacting a property-law solicitor (avocat).

What happens during a drought/clay survey in La Crau?

• On-site visit: survey and classification of your cracks, crack-width measurements, operational damage recorded at your home
• Context analysis: clay nature of the soil, the commune’s natural disaster declaration (Cat Nat) history (2 drought decrees), local dry spells that explain the timetable of the damage
• Costing of works: underpinning, injections, drains – with several scenarios depending on your budget
• A written report you can pass directly to your insurer or your solicitor

Independent expert, with no ties whatsoever to any building contractor. Request a visit in La Crau – also worth reading, 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 La Crau (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: La Crau 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 La Crau (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: La Crau 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 La Crau (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: La Crau 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 La Crau among the clay risk zones?

The Var is very broadly affected by the clay shrink-swell (RGA) hazard (BRGM map, viewable on georisques.gouv.fr). For La Crau, the 2 drought decrees recorded in GASPAR leave no doubt: the exposure is real, not merely theoretical.

Can a cracked house in La Crau be compensated under the natural disaster scheme?

Only if the damage corresponds to a period covered by a decree (the two latest recognised: 2018, 2023) and if the declaration was filed within 30 days. Failing that, the legal route against the seller remains – and there, precisely dating the damage through a survey becomes the decisive element.

Where do the figures quoted on this page come from?

The decrees come from the GASPAR database (Journal officiel, open data, 2025 update), the rainfall from Open-Meteo weather archives for the La Crau grid. Cassini Expertise merely reports them, without adjustment.

Find out more: Article 1641 of the Civil Code and the hidden defects warranty (garantie des vices cachés), explained.

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

📅 Last updated 06/11/2026 - Cassini Expertise, independent building expert – departments 06, 83 and 13.