Ollioules: Clay Soil, Subsidence and Cracks – Official Data

Ollioules and clay drought: should you be worried about your house?

Yes, if your house rests on shallow foundations and is showing cracks: Ollioules combines a clay soil classified at high exposure and 10 natural disaster declarations (Cat Nat) since 1982, including 3 drought prefectoral decrees (full list below). The rainfall figures confirm the at-risk scenario: three dry years out of four (2020, 2022, 2023), then an abrupt catch-up in 2024 with 827 mm (+22%) – exactly the alternation that cracks foundations in this village tucked between the cliffs.

Cassini Expertise, an independent firm, handles cracks and drought-related damage in Ollioules and across the whole of the Var. This page brings together the public data for the commune, with no sales talk, to help you work out whether your case calls for simple monitoring or a survey.

Is my cracked house in Ollioules linked to the drought decrees?

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

• 3 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 01/04/2019 (prefectoral decree of 29/04/2020)
  • event of 01/04/2022 (prefectoral decree of 03/04/2023)
• 7 prefectoral decrees related to flood and storm

What to do with it: look at the dates. If your cracks appeared in the 12 to 24 months following one of these periods (2017, 2019 or 2022), you have a potential Cat Nat file – provided you declared the loss to your insurer within 30 days of publication of the decree. If that deadline has passed, the route of a claim against the seller for hidden defect (vice caché) or fraud (dol) remains (see below). In both cases, keep your dated photos and your works invoices: this is what an expert and an insurer will ask you for first.

Is my plot classified at risk? The official clay classification (GéoRisques/BRGM)

The GéoRisques platform (BRGM) classifies Ollioules at high exposure to clay shrink-swell (RGA), with some sectors at medium exposure. This is the level insurers and notaires systematically check before covering or authenticating a sale – you can run the same check free of charge on georisques.gouv.fr by entering your address. Also worth noting: the commune is classified at radon potential class 3 (IRSN/GéoRisques data), a point to watch for indoor air quality, independently of any cracks.

This classification completes the decree history above: the hazard rating says what can happen, the decrees say what has already happened. If your plot is at high exposure and the commune has already seen several dry summers, the risk of damage to your property is no longer a theoretical hypothesis – it is a point to check before any works, purchase or sale.

Why every file in Ollioules has to be read through its local context

In Ollioules, my eye is drawn first to the commune’s very marked relief: the villas clinging to the slopes of the Gros Cerveau massif or the hills of la Reppe do not behave like the Provençal houses built in the agricultural plain towards le Las or the Brusc quarter. The estates of the 70s-80s, often built quickly on shallow foundations with no thorough soil survey, rest on the marly clays typical of the Var that work hard between summer and winter. In this area I have seen much differential settlement appear after a marked drought period, the clay ground shrinking on one side of the building while the other stays stable – especially where a hedge of pines or oaks planted too close to the foundations pumps the residual moisture from the ground. Recent renovation and extension programmes, frequent in the residential neighbourhoods near the old village, sometimes aggravate the phenomenon by changing the load distribution on ground that is already heterogeneous. The older stone Provençal buildings, with deeper foundations, overall resist better than the modern breeze-block constructions of the 80s, which are more sensitive to the ground movement linked to this swelling clay characteristic of the Ollioules basin.

Rainfall: the commune’s long memory

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.

Ollioules: 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)
• 🔴 04/2019 → 09/2019 – Drought – clay shrink-swell (RGA) (prefectoral decree of 29/04/2020)
• 🔴 04/2022 → 09/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 3 droughts and 7 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.

Forty years of decrees: the full chronology for Ollioules

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)
• 🔵 01/1999 → 01/1999 – Floods (prefectoral decree of 23/02/1999)
• 🔵 11/2011 → 11/2011 – Floods (prefectoral decree of 18/11/2011)
• 🔵 10/2012 – Floods (prefectoral decree of 10/01/2013)
• 🔵 09/2014 – Floods (prefectoral decree of 04/11/2014)
• 🔴 07/2017 → 09/2017 – 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 → 09/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 3 droughts and 7 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.

Damp, water ingress and rising damp in Ollioules

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 Ollioules and you may already have read online that resin injections are needed, or a mechanical ventilation system. My message: not so fast. Without a precise diagnosis of the cause, you risk paying for a pointless treatment that will solve nothing.

The 4 causes and how to recognise them

• Rising damp: water from the ground rises into the walls by capillary action. Stains climbing gradually from the bottom, often on older masonry with no damp-proof barrier, efflorescent salts visible at the foot of the wall.
• Water ingress: water enters from outside (roof, façade, joinery, terrace). Localised stains, often linked to rain episodes, halos on the ceiling or the upper parts of walls.
• Condensation: moisture in the air settles on cold surfaces where ventilation is insufficient. Frequent in bathrooms, kitchens, poorly aired rooms; mould in wall corners and around windows.
• Leak: a defective pipe or drain. A localised stain near a bathroom, a kitchen or a downpipe, sometimes with a persistent smell.

The trap of the diagnosis sold by the treatment contractor

In Ollioules as elsewhere, many companies focused on damp treatment offer a “free quote”. The problem: that diagnosis is carried out by the company that will then sell you the treatment. The conflict of interest is structural, and the outcome is often the same – a recommendation of resin injections whatever the real cause, even when it is actually water ingress or a ventilation defect. A proper diagnosis must be independent of any sale of works, to identify the exact cause before money is committed.

Before commissioning damp-treatment works, request an independent diagnosis in Ollioules to pinpoint the origin of the problem. To go further, read our damp guide for 06, 83 and 13.

The official clay classification (GéoRisques/BRGM)

The GéoRisques platform (BRGM) classifies Ollioules 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 exposure to clay shrink-swell (RGA)

The GéoRisques platform (BRGM) classifies Ollioules 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.

Why cracks often appear after a dry summer: the local weather

Annual rainfall measured on the Ollioules weather grid (Open-Meteo source):

• 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, with a low point in 2020 (482 mm)
• Three consecutive or near-consecutive years of water deficit: 482 mm in 2020, 559 mm in 2022, 577 mm in 2023
• Then a clear rebound in 2024, at 827 mm (+22%)

In practice, the phenomenon plays out in two stages: the dry summer dries out the clay at depth, the ground shrinks and the first cracks appear; then the return of the rain rehydrates the ground at a stroke, causing swelling and fresh differential movement. If your villa dates from 1970-2000 and rests on shallow foundations, it is the one that takes the strain first – often 12 to 24 months after the dry spell. Remember this window of time: it is what links a recent crack to a specific dry summer, and therefore to a possible decree.

Drought right now (as at 04/10/2026)

In the commune: recent rain (3 days ago). Rainfall over the last 30 days: 27 mm, against roughly 53 mm expected at this time of year – a 49% 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: 27 mm, against roughly 54 mm expected at this time of year – a 50% 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 (5 days ago). Rainfall over the last 30 days: 68 mm, against roughly 61 mm expected at this time of year – an 11% 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.

This week’s drought watch (as at 19/10/2026)

In the commune: recent rain (1 day ago). Rainfall over the last 30 days: 78 mm, against roughly 67 mm expected at this time of year – a 16% 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.

Which crack signs should alert me in Ollioules?

• A stair-step crack, passing through the wall, open by more than 2 mm – measure it with a ruler, this is the threshold from which we speak of structural damage
• A crack that evolves over time: fit a plaster tell-tale or take a dated photo every month for a season
• Other signals not to neglect: doors and windows sticking, tiles splitting diagonally, render coming away
• Aggravating factors on your plot: a house built on clay, trees near the façade, insufficient drainage around the foundations

With 3 drought prefectoral decrees already recognised in the commune, as soon as two or three of these signs build up at your property, call in an expert before any repair – and before any purchase or sale negotiation. Repairing without a diagnosis often amounts to painting over a problem that will reappear.

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

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

• Hidden defect (article 1641 of the Code civil): serious cracks, not detectable at the viewing, predating the sale → price reduction or cancellation of the sale. You have 2 years after discovering the damage to act – not 2 years after the purchase.
• Fraud (dol) (article 1137): the seller knew and concealed the damage → cancellation of the sale and damages, within a 5-year deadline; the commune’s GASPAR decree then underpins your file by proving the risk was known.

First step in both cases: have the cracks dated and characterised by an independent expert, before contacting a property-law solicitor (avocat). Without this technical report, proving the damage predates the sale is difficult.

What happens during a drought/clay survey in Ollioules?

• On-site visit: crack survey and classification, crack-width measurements, associated functional damage
• Context analysis: clay nature of the soil, the commune’s natural disaster declaration (Cat Nat) history (3 drought decrees), past local droughts
• Works estimate: underpinning, injections, drains – several costed scenarios to compare options before committing
• A written report you can pass to your insurer or your solicitor, to support a Cat Nat claim or an action against the seller

Independent expert, with no ties to any building contractor whatsoever. Request a visit in Ollioules – also worth reading, our complete guide to RGA and Cat Nat in 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 Ollioules (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: Ollioules 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, second-opinion expert assessments. 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 Ollioules (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: Ollioules 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 Ollioules in an at-risk clay zone?

Yes. A large part of the Var is affected by the clay shrink-swell (RGA) hazard (BRGM map viewable on georisques.gouv.fr). In Ollioules, the 3 drought decrees recorded in GASPAR confirm the risk is anything but theoretical: it has already materialised three times since 2017.

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

Only if your damage can be tied to a period covered by a decree (the latest recognised: events 2017, 2019, 2022, decrees published in 2018, 2020, 2023) and if you filed your declaration within 30 days of publication. If not, you must turn to an action against the seller (hidden defect or fraud (dol)) – and having the damage precisely dated by an expert then becomes the decisive step in your file.

Can the figures quoted on this page be checked?

Yes, you can cross-check them yourself: the decrees come from the GASPAR database (Journal officiel, open data, 2025 update), the rainfall from Open-Meteo weather archives for the Ollioules 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.