Le Muy: Clay Soil, Subsidence and Cracks – Official Data

Cracked house in Le Muy: drought or something else? What the decrees and the rain say

Le Muy combines a clearly identified clay zone and a substantial natural disaster record: the GASPAR database records 2 drought prefectoral decrees (full list below) and 7 flood decrees, i.e. 9 in total. On the weather side, three dry years in a row (2020, 2022, 2023) followed by a clear catch-up in 2024 with 1,085 mm (+39%) – exactly the scenario that puts foundations under strain at the gateway to the Argens. If your house cracks after this kind of alternation, here is how to check it and what to do.

Cassini Expertise, an independent building expert, handles cracks and drought-related damage in Le Muy and throughout the Var. This page sets out the official data specific to the commune, adding nothing commercial.

How many natural disaster declarations (Cat Nat) in Le Muy, and what use is it to you?

The GASPAR database (decrees published in the Journal officiel since 1982) attributes 9 natural disaster declarations (Cat Nat) to the commune of Le Muy:

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

In practical terms: if your cracks appeared during one of these two periods (mid-2017 or early 2022), keep the dates of appearance carefully – dated photos, email to the insurer, quotes from the time. This is what ties the file to the decree. Two routes then: natural disaster declaration (Cat Nat) compensation (provided you declared within 30 days), or failing that an action against the seller for hidden defect (vice caché) or fraud (dol) if the property has changed hands since.

Is Le Muy in an at-risk clay zone? What the official map says

The GéoRisques platform (BRGM) classifies Le Muy 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 – check it before buying by entering your address on georisques.gouv.fr. Also worth noting: radon potential class 3 across the commune (IRSN/GéoRisques data) – think about a radon measurement if you spend time in a basement or a poorly ventilated ground floor.

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 – and therefore all the easier to have recognised.

The complete chronology of the 9 natural disasters recognised in Le Muy

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

• 🔵 09/1992 → 09/1992 – Floods (prefectoral decree of 23/06/1993)
• 🔵 01/1994 → 01/1994 – Floods (prefectoral decree of 08/03/1994)
• 🔵 01/1996 → 01/1996 – Floods (prefectoral decree of 02/02/1996)
• 🔵 06/2010 → 06/2010 – Floods (prefectoral decree of 21/06/2010)
• 🔵 11/2011 → 11/2011 – Floods (prefectoral decree of 18/11/2011)
• 🔵 01/2014 → 01/2014 – Floods (prefectoral decree of 31/01/2014)
• 🔴 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)
• 🔴 01/2022 → 09/2022 – Drought – clay shrink-swell (RGA) (prefectoral decree of 03/04/2023)

Expert reading: 2 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.

The official clay classification (GéoRisques/BRGM)

The GéoRisques platform (BRGM) classifies Le Muy 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 Le Muy 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 393 mm over the year, against a local average of 759 mm. 2022 ranks as the 8th driest year out of 35 (568 mm against an average of 759 mm); 2023 follows in 11th place (604 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 Le Muy

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 Le Muy and are looking for a solution. Before signing any quote, you first need to understand what is really happening in your wall. Treatment contractors often offer a single solution whatever the real cause.

The 4 causes and how to recognise them

• Rising damp: stains climbing from the bottom of the wall, generally stopping between 1 and 1.5 metres, often accompanied by efflorescent salts and disintegrating render.
• Water ingress: localised stains near a roof, a cracked façade or joinery, that worsen after rain.
• Condensation: misted windows, mould in corners and poorly ventilated bathrooms, with no link to the ground.
• Leak: a pinpoint stain near a pipe or under a wet room, that evolves independently of the weather.

The trap of the diagnosis sold by the treatment contractor

In Le Muy as elsewhere, many companies selling resin injections or drainage systems carry out the diagnosis themselves. The risk: they have an interest in concluding rising damp, even when the real cause is water ingress or condensation poorly dealt with upstream. The result: costly works that solve nothing.

Before commissioning works, have an independent diagnosis in Le Muy drawn up by an expert who sells no treatment. To understand the mechanisms and the solutions suited to each case in detail, read our damp guide for 06, 83 and 13.

Le Muy: ground conditions that demand local knowledge

In Le Muy, between the first relief of the Var back-country and the agricultural plain sloping down to the Argens, I have been able to observe on many sites that the soil is particularly sensitive to changes in moisture. The commune saw strong residential development from the 70s-80s, with Provençal villas and more recent constructions set on gently sloping or piedmont ground, often on shallow foundations that were not always matched to the nature of the soil. The vegetation typical of the area, with its umbrella pines and oaks that draw huge amounts of water from depth at the slightest dry spell, intensifies the shrinkage of the clay around the homes closest to these trees. We regularly work on Le Muy houses where differential settlement shows up on the façade, typically as summer approaches or after several consecutive dry seasons, when the clay contracts beneath the footings and generates localised structural movement. The estates built as extensions of the old centre, often on fill or ground reworked during the developments of recent decades, are particularly exposed to this damage, which explains the frequency of the cracks observed in this part of the Var.

Why cracks appear after the rain and not during the drought

Annual rainfall recorded on the Le Muy weather grid (Open-Meteo data):

• 2019: 1,105 mm · 2020: 607 mm · 2021: 706 mm · 2022: 568 mm · 2023: 604 mm · 2024: 1,085 mm
• Average over the period: 779 mm/year, driest year: 2022 (568 mm)
• Three years of marked deficit (2020, 2022, 2023): 607 mm, 568 mm, then 604 mm
• Sharp catch-up in 2024: 1,085 mm, i.e. +39%

Shrink-swell plays out in two acts: the drought dries out the clay at depth, the ground shrinks and the first cracks appear; then the rain returns, rehydrates the ground at a stroke, and this swelling triggers fresh differential movement. The 1970-2000 villas, built on shallow foundations, are in the front line – often with a lag of 12 to 24 months after the weather episode. In other words: a crack appearing today may well date from the 2022-2023 drought, not from a recent construction defect.

Crack in Le Muy: worry, or wait?

• A stair-step crack, passing through the wall, open by more than 2 mm → worry
• A crack that evolves over time → fit a tell-tale (band of plaster or gauge) and monitor for several months before concluding
• associated signs to watch at the same time: doors and windows sticking, tiles splitting diagonally, render coming away or bulging
• aggravating factors to check around the house: clay ground, trees close by, failed drainage at the foot of the foundations

With two drought prefectoral decrees already recognised in the commune, a build-up of several of these signs justifies a survey before any repair – and before signing anything, whether buying or selling.

Cracked house in Le Muy: what to do when buying or selling?

With recent drought decrees and sales continuing, some properties change hands concealing existing damage. If you discover cracks after signing, the buyer has two routes:

• Hidden defect (article 1641 of the Code civil): serious cracks, not visible at the viewing, that appeared before the sale → price reduction or cancellation, to be claimed within 2 years of discovery
• Fraud (dol) (article 1137): the seller knew and said nothing → cancellation of the sale and damages, 5-year deadline; the commune’s GASPAR decree then helps underpin the file

Before launching proceedings, have the damage dated and characterised by an expert: this dating decides whether you are within the deadlines and in which scenario you fall. For what follows, a property-law solicitor (avocat) takes over.

How a drought/clay survey unfolds in Le Muy

• On-site visit: crack survey and classification, crack-width measurement, associated functional damage
• Context analysis: clay nature of the soil, the commune’s natural disaster declaration (Cat Nat) history (2 drought decrees), local drought episodes
• Works estimate: underpinning, injections, drains – with several costed scenarios
• A written report, directly usable by the insurer or the solicitor

Independent expert, with no ties to any building contractor. Request a visit in Le Muy – 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 Le Muy (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: Le Muy 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.

Frequently asked questions

Is Le Muy among the at-risk clay zones?

The Var is very broadly affected by the clay shrink-swell (RGA) hazard (BRGM map viewable on georisques.gouv.fr). In Le Muy, the 2 drought decrees already recognised by GASPAR show the risk is anything but theoretical.

Is my cracked house in Le Muy eligible for compensation under the natural disaster scheme?

Only if the damage goes back to a period covered by a decree (the latest recognised drought periods: 2018, 2023) and if the declaration was filed within 30 days. Failing that, the action against the seller remains – and there, everything rests on the dating of the damage by an expert.

Can the figures quoted here be checked independently?

Yes: the decrees come from the GASPAR database (Journal officiel, open data, 2025 update), the rainfall from Open-Meteo weather archives for the Le Muy grid. Cassini Expertise reproduces these data as they stand, without adjustment.

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

In the commune: recent rain (3 days ago). Rainfall over the last 30 days: 9 mm, against roughly 57 mm expected at this time of year – an 84% 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.

Where do the rains stand? (as at 05/10/2026)

In the commune: recent rain (4 days ago). Rainfall over the last 30 days: 9 mm, against roughly 59 mm expected at this time of year – an 85% 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.

Where do the rains stand today? (as at 12/10/2026)

In the commune: recent rain (3 days ago). Rainfall over the last 30 days: 107 mm, against roughly 69 mm expected at this time of year – a 55% 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 (2 days ago). Rainfall over the last 30 days: 110 mm, against roughly 80 mm expected at this time of year – a 38% 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.

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.