Toulon: Clay Soil, Subsidence and Cracks – Official Data

Toulon, drought and clay: is your cracked house affected?

If your house is in Toulon and it is starting to crack, the answer comes down to one figure: the commune has experienced 5 drought prefectoral decrees (full list below) and 13 flood decrees, i.e. 18 natural disaster declarations (Cat Nat) – a heavy, well-documented track record. Local rainfall figures explain the mechanism: three dry years in a row (2020, 2022, 2023), then a rebound to 827 mm in 2024. It is precisely this drought/rain alternation that puts foundations under strain around the rade (bay) and on the slopes of Mont Faron.

Cassini Expertise, an independent building expert, diagnoses cracks and drought-related damage in Toulon and across the whole of the Var. This page sets out the official data specific to the commune, exactly as published – keep it to hand if you need to put an insurance file together or negotiate with a seller.

Could my house be linked to a natural disaster declaration (Cat Nat) in Toulon?

The first thing to check, before anything else: how far back do your cracks date? The GASPAR database (decrees published in the Journal officiel, the French Official Gazette, since 1982) records 18 natural disaster declarations (Cat Nat) for the commune of Toulon:

• 5 drought prefectoral decrees (differential ground movement linked to clay shrink-swell (RGA))
  • event of 01/01/1998 (prefectoral decree of 06/07/2001)
  • event of 01/07/2017 (prefectoral decree of 18/09/2018)
  • event of 01/07/2019 (prefectoral decree of 29/04/2020)
  • event of 01/01/2020 (prefectoral decree of 18/05/2021)
  • event of 01/04/2022 (prefectoral decree of 03/04/2023)
• 13 flood prefectoral decrees and storm

In practical terms: if your cracks appeared during one of the periods above, you can claim natural disaster declaration (Cat Nat) compensation, provided you declared the loss within the statutory deadlines. If the period does not match, or if you are buying a property that is already cracked without knowing it, the remaining route is a claim against the seller, for hidden defect (vice caché) or fraud (dol) – see further down.

Is my plot classified as a clay zone in Toulon?

Go and check on georisques.gouv.fr: the GéoRisques platform (BRGM) classifies Toulon at high exposure to clay shrink-swell (RGA), with some sectors at medium exposure. This is the level your insurer and your notaire (French notary) already look at to judge the risk on your plot. Another point not to overlook: the commune also sits in radon potential class 3 (IRSN/GéoRisques data) – worth having measured if you are buying or if you spend time in a basement or on the ground floor.

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 in a high-exposure area and has come through one or more dry summers, the risk of damage is all the more likely – and all the more documented.

Toulon: 18 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):

• 🔴 01/1998 → 12/1998 – Drought – clay shrink-swell (RGA) (prefectoral decree of 06/07/2001)
• 🔴 07/2017 → 09/2017 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/09/2018)
• 🔴 07/2019 → 09/2019 – Drought – clay shrink-swell (RGA) (prefectoral decree of 29/04/2020)
• 🔴 01/2020 → 06/2020 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/05/2021)
• 🔴 04/2022 → 09/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 5 droughts and 13 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 18 natural disasters recognised in Toulon

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)
• 🔵 10/1988 → 10/1988 – Floods (prefectoral decree of 22/02/1989)
• 🔵 09/1992 → 09/1992 – Floods (prefectoral decree of 23/06/1993)
• 🔴 01/1998 → 12/1998 – Drought – clay shrink-swell (RGA) (prefectoral decree of 06/07/2001)
• 🔵 01/1999 → 01/1999 – Floods (prefectoral decree of 16/04/1999)
• 🔵 09/2006 → 09/2006 – Floods (prefectoral decree of 22/02/2007)
• 🔵 12/2008 → 12/2008 – Floods (prefectoral decree of 17/04/2009)
• 🔵 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 04/12/2014)
• 🔴 07/2017 → 09/2017 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/09/2018)
• 🔴 07/2019 → 09/2019 – Drought – clay shrink-swell (RGA) (prefectoral decree of 29/04/2020)
• 🔵 10/2019 → 10/2019 – Floods (prefectoral decree of 30/10/2019)
• 🔴 01/2020 → 06/2020 – Drought – clay shrink-swell (RGA) (prefectoral decree of 18/05/2021)
• 🔵 10/2021 → 10/2021 – Floods (prefectoral decree of 20/12/2021)
• 🔴 04/2022 → 09/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)
• 🔵 10/2023 – Floods (prefectoral decree of 22/12/2023)

Expert reading: 5 droughts and 13 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.

What the official clay mapping says

The GéoRisques platform (BRGM) classifies Toulon 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 Toulon 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 is my house moving now? Local rainfall

Annual rainfall recorded on the Toulon 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 years of marked deficit: 482 mm in 2020, 559 mm in 2022, 577 mm in 2023
• then a clear catch-up in 2024, at 827 mm (+22%)

Remember this two-stage mechanism, it explains why cracks often appear after the event: the drought dries out the clay at depth, which triggers shrinkage and the first cracks; then the return of the rain rehydrates the ground abruptly, causing swelling and fresh differential movement. If you live in a villa built between 1970 and 2000 on shallow foundations, yours is the house that takes the strain first – with a lag of 12 to 24 months after the dry spells. In other words: a crack appearing today may well date from the dry summer of a year or two ago.

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

In the commune: recent rain (3 days ago). Rainfall over the last 30 days: 28 mm, against roughly 53 mm expected at this time of year – a 47% 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: 28 mm, against roughly 54 mm expected at this time of year – a 48% 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: 93 mm, against roughly 61 mm expected at this time of year – a 52% 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: 108 mm, against roughly 67 mm expected at this time of year – a 61% 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: 26 years of measurements, a well-documented context

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.

Toulon: ground conditions that demand local knowledge

In Toulon, we regularly work on villas built between the 1960s and 1980s, tucked onto the foothills of Mont Faron or Mont Coudon, as well as on the more recent housing estates that spread towards Valbertrand, La Rode or Sainte-Musse by filling in the valleys and the former agricultural land. This contrasting relief, between limestone hills and pockets of clay ground at the bottom of the valleys, creates soil heterogeneity that seriously complicates the bearing-capacity study before construction. Many of these buildings rest on shallow foundations, designed at a time when the sensitivity of clays to shrink-swell was not systematically factored into geotechnical surveys. We also see that the surrounding Mediterranean vegetation, in particular pine and olive trees planted too close to load-bearing walls, intensifies the drying-out of the soil during summer drought, which encourages differential settlement under the corners of façades. The Toulon coastline, with its warm climate and increasingly pronounced summers, particularly exposes slab-built individual houses to this breathing effect of clay soil: swelling in winter, shrinking in summer. It is precisely this alternation that explains the recurring stair-step cracks on gable walls and around openings that we record every year in this area, far more than in zones with more homogeneous ground.

Rainfall: the commune’s long memory

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 701 mm. 2022 ranks as the 12th driest year out of 35 (559 mm against an average of 701 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 Toulon

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.

A reader describes damp marks on a wall in Toulon. Before signing up for a resin-injection quote or installing mechanical ventilation, you need to know where the problem really comes from. Treating the wrong cause means spending several thousand euros for nothing.

The 4 causes and how to recognise them

• Rising damp: stains at the base of the wall, up to 1 m high, often in older properties without a damp-proof course, with efflorescent salts and blistering render.
• Water ingress: localised halo-shaped marks on the exposed side of the façade, often linked to a crack, a flat roof or a defective gutter, worse after rain.
• Condensation: misted windows, mould in corners and bathrooms, typical of a poorly ventilated home, with no link to rainfall.
• Leak: a stain that spreads progressively, a smell, sometimes linked to a buried pipe or a chased-in run, independent of the weather.

The trap of the diagnosis sold by the treatment contractor

In Toulon as elsewhere, many resin-injection companies offer a “free quote”. The problem: that diagnosis is carried out by the same firm that then sells you the treatment. The classic outcome: rising damp is diagnosed when it is actually water ingress or condensation, and the customer pays for a pointless resin injection that solves nothing.

An independent diagnosis, with no commercial interest in selling one particular treatment, identifies the true cause before any works are commissioned. If you are in Toulon and unsure about the origin of your damp, contact us for an independent diagnosis. To go further, read the damp guide for 06, 83 and 13.

Is my crack serious? The warning signs

• A stair-step crack, passing through the wall, open by more than 2 mm
• A crack that evolves over time – fit a tell-tale (plaster patch or gauge) and check it over several months
• Associated signs to watch at the same time: doors and windows sticking, tiles splitting diagonally, render bulging
• Aggravating factors at your property: clay soil, a tree close to the house, failed drainage around the foundations

With 5 drought prefectoral decrees recorded for the commune, a build-up of several of these signals justifies calling in an expert before any repair – and before any buying or selling decision, so the problem is not discovered after signing.

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

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

• Hidden defect (article 1641 of the Code civil): serious cracks, not visible at the viewing, predating the sale → you can claim a reduction in the price or the cancellation of the sale, within 2 years of discovering them
• Fraud (dol) (article 1137): the seller knew about the damage and concealed it → cancellation and damages, within 5 years; the commune’s GASPAR decree then helps underpin your case

In both cases, the first step is to have the damage dated by an independent expert; the next step, to build the legal case, is to appoint a property-law solicitor (avocat).

What happens during a drought/clay survey in Toulon?

• Technical visit: crack survey and classification, crack-width measurements, functional damage
• Context analysis: clay zone, the commune’s natural disaster declaration (Cat Nat) history (5 drought decrees), local drought episodes
• Costing of works: underpinning, injections, drains – with several scenarios depending on your budget
• A written report, directly usable by your insurer or your solicitor

For an on-site survey: building expert in Toulon.

Independent expert, with no ties to any building contractor. Request a visit in Toulon – 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 Toulon (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: Toulon 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 Toulon (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: Toulon 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 Toulon in an at-risk clay zone?

Yes. The Var is broadly affected by the clay shrink-swell (RGA) hazard (BRGM mapping, viewable on georisques.gouv.fr). For Toulon, the GASPAR history – 5 recognised drought decrees – confirms that the risk is anything but theoretical: check your address on georisques.gouv.fr before buying or commissioning works.

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

Only if your damage can be tied to a period covered by a decree (the latest recognised drought periods: 2001, 2018, 2020, 2021, 2023) and if you declared the loss within 30 days. If not, the remaining route is the claim against the seller – and there, having the damage precisely dated by a survey becomes the crux of the file.

Can this data be verified?

Yes, and you can cross-check it yourself: the decrees come from the GASPAR database (Journal officiel, open data sets, 2025 update), the rainfall from Open-Meteo weather archives for the Toulon grid. Cassini Expertise does not adjust these figures.

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.