Mougins: Clay Soil, Subsidence and Cracks – Official Data

The official clay shrink-swell exposure rating

The GéoRisques platform (BRGM) classifies Mougins as high exposure to clay shrink-swell (RGA – retrait-gonflement des argiles), with some sectors at medium exposure. This is the reference level used by insurers and notaires to assess the risk on a plot. Note also: radon potential of class 3 in the commune (IRSN/GéoRisques data) – a health-and-building watch point in the areas concerned.

This zoning completes the decree record above: the hazard level tells you what can happen, the decrees tell you what has already happened. A house in a “high exposure” area that has been through one or more dry summers carries a risk of damage that is all the better documented.

What the official clay mapping says

The GéoRisques platform (BRGM) classifies Mougins as high exposure to clay shrink-swell, with some sectors at medium exposure. This is the reference level used by insurers and notaires to assess the risk on a plot. Note also: radon potential of class 3 in the commune (IRSN/GéoRisques data) – a health-and-building watch point in the areas concerned.

This zoning completes the decree record above: the hazard level tells you what can happen, the decrees tell you what has already happened. A house in a “high exposure” area that has been through one or more dry summers carries a risk of damage that is all the better documented.

Mougins: ground that demands a local reading

In Mougins, twenty-five years in the trade tell us that every area has its own cracking logic – and here it starts with the relief. The commune steps down from the perched old village to the wooded hills of umbrella pines and holm oaks that slope towards the Brague plain: the 1970s-80s Provençal villas built on these slopes very often rest on shallow foundations, sometimes no more than strip footings, never designed for the swelling clay found at depth in these foothill grounds. When a prolonged drought dries out this clay soil, it shrinks, and the moisture differences between the sun-exposed façade and the one kept in the shade of the canopy cause differential settlement that shows up as the typical stair-step cracks, often at the corners of openings and above the lintels. The more recent estates, built on cut-and-fill earthworks to fit the relief, add another source of disorders: the backfilled part settles differently from the natural ground, and houses straddling the two zones absorb these movements sideways on. We are regularly called to villas in the residential neighbourhoods of Mougins le Haut or around the Golf, where the density of trees with powerful roots compounds the soil’s summer moisture suction still further.

Rainfall: the commune’s long memory

Weather archives for the area cover 35 complete years (1991-2025). The driest ever recorded: 2017, with 475 mm of rain over the year, against a local average of 908 mm. 2022 ranks as the 3rd driest year out of 35 (600 mm vs a 908 mm average); 2023 follows in 4th place (635 mm).

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

The complete timeline of the 26 natural disasters recognised in Mougins

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

• 🔵 11/1982 → 11/1982 – Cyclones / Storms (decree of 15/12/1982)
• 🔵 10/1987 → 10/1987 – Floods (decree of 02/12/1987)
• 🔵 10/1993 → 10/1993 – Floods (decree of 19/10/1993)
• 🔵 06/1994 → 06/1994 – Floods (decree of 29/06/1994)
• 🔵 01/1996 → 01/1996 – Floods (decree of 02/02/1996)
• 🔵 12/1996 → 12/1996 – Floods (decree of 24/03/1997)
• 🔵 10/1999 → 10/1999 – Floods (decree of 03/03/2000)
• 🔵 11/2000 → 11/2000 – Floods (decree of 19/12/2000)
• 🔵 12/2000 → 12/2000 – Floods (decree of 29/08/2001)
• 🔴 01/2004 → 03/2004 – Drought (RGA – clay shrink-swell) (decree of 26/06/2008)
• 🔴 07/2004 → 09/2004 – Drought (RGA – clay shrink-swell) (decree of 26/06/2008)
• 🔵 08/2004 – Floods (decree of 11/01/2005)
• 🔴 01/2005 → 03/2005 – Drought (RGA – clay shrink-swell) (decree of 26/06/2008)
• 🔵 09/2005 → 09/2005 – Floods (decree of 10/10/2005)
• 🔵 12/2005 → 12/2005 – Floods (decree of 05/05/2006)
• 🔴 07/2007 → 09/2007 – Drought (RGA – clay shrink-swell) (decree of 07/08/2008)
• 🔵 09/2009 – Floods (decree of 10/11/2009)
• 🔵 11/2011 → 11/2011 – Floods (decree of 18/11/2011)
• 🔵 10/2012 – Floods (decree of 10/01/2013)
• 🔵 11/2014 – Floods (decree of 17/02/2015)
• 🔵 10/2015 – Floods (decree of 07/10/2015)
• 🔵 11/2019 → 11/2019 – Floods (decree of 28/11/2019)
• 🔵 12/2019 → 12/2019 – Floods (decree of 12/12/2019)
• 🔴 04/2022 → 09/2022 – Drought (RGA – clay shrink-swell) (decree of 21/07/2023)
• 🔴 04/2023 → 06/2023 – Drought (RGA – clay shrink-swell) (decree of 18/06/2024)
• 🔵 09/2024 – Floods (decree of 15/12/2024)

How an expert reads this: 6 droughts and 20 floods. Clusters (several decrees close together) mark crisis periods – the summer sequence 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 route is a claim against the seller.

Damp, water ingress and rising damp in Mougins

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 a stain, a musty smell or saltpetre on a wall in Mougins. You may already have read that you need resin injections or mechanical ventilation. Our message: not so fast. Treating the wrong cause means spending several thousand euros for nothing – and seeing the problem come back six months later.

The 4 causes and how to recognise them

• Rising damp: ground water climbs into the masonry by capillary action. Typical sign: a tide mark starting at the base of the wall, usually stopping between 80 cm and 1.50 m, with saltpetre and blistering render. Frequent in the older houses of Mougins with no damp-proof course.
• Water ingress: water enters from outside – roof, cracked façade, poorly waterproofed terrace, blocked gutter. The stain often follows a slope or appears after rain, not necessarily at the bottom of the wall.
• Condensation: the damp comes from poorly ventilated indoor air condensing on cold surfaces. Typical of bathrooms, kitchens, or rooms poorly aired in winter. No sharp tide mark, rather a diffuse surface mould.
• Leak: a defective pipe, drain or joint. A localised mark, often near a shower room or kitchen, that can appear at any height on the wall.

The trap of the diagnosis sold by the treatment contractor

In Mougins as elsewhere, many owners call a damp treatment company directly. The problem: that company will inevitably sell you a solution from its own catalogue – injections, drainage, tanking – even if the real cause is a simple roof leak that would cost 300 euros to repair. The diagnosis is never neutral when it is made by whoever then bills for the works.

Before committing any money, have an independent diagnosis carried out in Mougins by an expert who has nothing to sell but his analysis: request an independent survey. To go further, also read our damp guide for the 06, 83 and 13, which details the diagnostic methods and the treatments suited to each cause.

Mougins: clay shrink-swell and cracks, what the decrees reveal

Mougins combines a clearly identified clay zone with a substantial Cat Nat record: the GASPAR database counts 6 drought decrees (full list below) and 20 flood decrees, i.e. 26 natural disaster (Cat Nat) decrees. The weather records fit the scenario: 4 dry years in a row (2020 to 2023), then a sharp return to 1,239 mm in 2024 (+50%) – exactly the type of alternation that puts foundations to work in Picasso’s perched village.

If your house in Mougins shows cracks, these figures tell you straight away whether the ground is to blame or not. Cassini Expertise, an independent building expert, handles cracks and drought-related damage in Mougins and across the whole of the 06. This page brings together the official data for the commune: keep it to hand before calling an expert, an insurer or a lawyer.

Is my house covered by a natural disaster decree in Mougins?

The GASPAR database (decrees published in the Journal officiel since 1982) lists 26 natural disaster decrees for the commune:

• 6 drought decrees (differential ground movement linked to clay shrink-swell)
  • event of 01/01/2004 (decree of 26/06/2008)
  • event of 01/07/2004 (decree of 26/06/2008)
  • event of 01/01/2005 (decree of 26/06/2008)
  • event of 01/07/2007 (decree of 07/08/2008)
  • event of 01/04/2022 (decree of 21/07/2023)
  • event of 01/04/2023 (decree of 18/06/2024)
• 20 flood decrees and storm

What to do with this: look at when your cracks appeared and compare it with these periods. If they match a window covered by a decree, two paths open up: Cat Nat compensation (provided you declared the claim to your insurer within 30 days), or, if that deadline has passed, an action against the seller for hidden defect (vice caché) or fraudulent concealment (dol). An expert can date the damage precisely to point you to the right option.

Is my plot in Mougins classified as a clay risk zone?

The GéoRisques platform (BRGM) classifies Mougins as high exposure to clay shrink-swell, with some sectors at medium exposure. This is the reference level your insurer and your notaire already consult to assess the risk on your plot – you can check the exact address yourself on georisques.gouv.fr before any viewing. Another point to bear in mind if you are buying or building: radon potential of class 3 in the commune (IRSN/GéoRisques data), a subject to check with a surveyor.

This zoning completes the decree record above: the hazard level tells you what can happen, the decrees tell you what has already happened. A house in a “high exposure” area that has already been through one or more dry summers carries a risk of damage that is all the better documented – to be declared explicitly if you are selling.

Why do cracks appear after the drought, not during it?

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

• 2019: 1,167 mm · 2020: 679 mm · 2021: 639 mm · 2022: 600 mm · 2023: 635 mm · 2024: 1,239 mm
• Average over the period: 826 mm/year, low point in 2022 (600 mm)
• Four consecutive years of water deficit: 679 mm in 2020, 639 mm in 2021, 600 mm in 2022, 635 mm in 2023
• Then a rebound to 1,239 mm in 2024, i.e. +50%

The phenomenon plays out in two stages. The drought dries the clay at depth: it shrinks, the first cracks appear. Then the rain returns and rehydrates the ground at once – swelling, differential movement. Villas on shallow foundations, the majority of the 1970s-2000 stock, take the hit first, often 12 to 24 months behind the weather event. In plain terms: if your house was built in that period, keep an eye on it even a year or two after a dry summer.

Cracks in Mougins: when to worry and call an expert

• A stair-step crack, passing through the wall, wider than 2 mm
• A crack that moves (fit a plaster or glass tell-tale and check it after several months)
• associated signs: doors and windows that stick, floor tiles splitting diagonally, render coming away in bulges
• Clay ground, trees close to the house, defective drainage

With 6 drought decrees already recognised in the commune, a combination of several of these signs alone justifies a survey – before any repair (which can mask the real cause), and before any buying or selling decision.

Buying or selling in Mougins with visible cracks: what are my rights?

Between the latest drought decrees and the volume of transactions under way, many properties change hands without the damage being mentioned. If you are the buyer and discover cracks after signing, two legal levers exist:

• Hidden defect (vice caché, Article 1641 of the French Civil Code): serious cracks, not visible at the viewing, that predate the sale → price reduction or cancellation of the sale, action possible within 2 years of discovery
• Fraudulent concealment (dol, Article 1137): the seller knew and said nothing → cancellation plus damages, 5-year time limit; the commune’s GASPAR decree record then supports the file

First practical step: have the damage dated by a building expert – an indispensable piece for the file. For the rest, the legal side is handled with a French property lawyer.

How does a drought/clay survey work in Mougins?

• On-site visit: crack mapping and classification, width measurements, recorded functional disorders
• Context: the clayey nature of the ground, the commune’s Cat Nat history (6 drought decrees), local drought episodes
• Costed estimate of works: underpinning, injections, drainage – several scenarios depending on severity
• A written report, directly usable by the insurer or the lawyer

For an on-site visit: building expert in Mougins.

Independent expert, no ties to any repair company: the report stays objective, not a pretext for selling works. Request a visit in Mougins – also read our complete guide on RGA and Cat Nat in the 06, 83 and 13.

Soil surveys on clay ground: what the regulations say

The requirement for a preliminary geotechnical survey has applied since 1 October 2020 (ELAN law, art. 68); the new exposure map of 1 July 2026 widens its scope. This requirement, introduced by the ELAN law no. 2018-1021, article 68 (decree no. 2019-495 of 22 May 2019), applies particularly to Mougins (high exposure under the BRGM classification).

• What it changes for building: a soil survey is no longer optional – the ELAN law makes it compulsory in exposed zones for any sale of unbuilt land and any 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 ground is a medium-term cracking risk.
• What it changes for sellers: the absence of a survey on a property built before the requirement is not a defect in itself – but if damage appears, a seller who knew about it and concealed it exposes themselves to a claim for fraudulent concealment (dol).
• The link with the data above: Mougins combines high exposure with a documented record 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 what was actually built, damage surveys on clay ground, second-opinion expert assessments. Request a consultation.

Frequently asked questions

Is Mougins among the clay risk zones?

The Alpes-Maritimes is very widely affected by the clay shrink-swell hazard (BRGM map, consultable on georisques.gouv.fr). For Mougins, the 6 drought decrees recorded in GASPAR leave no doubt: the risk is real, not theoretical. Check your exact plot on georisques.gouv.fr before buying or starting works.

Is my cracked house in Mougins eligible for natural disaster compensation?

Only if the damage corresponds to a period covered by a decree (the last recognised drought periods: 2008, 2023, 2024) and if the declaration was made within 30 days. Failing that, the action against the seller remains – and there, everything rests on the expert dating of the damage.

Can the figures quoted on this page be checked independently?

Yes. The decrees come from the GASPAR database (Journal officiel, open data sets, updated 2025), and the rainfall figures from the Open-Meteo archives for the Mougins grid. Cassini Expertise simply compiles them, without altering them.

Weekly drought update (as at 04/10/2026)

In the commune: no significant rain for 25 days. Rainfall over the last 30 days: 3 mm, against roughly 57 mm expected at this time of year – a 95% deficit.

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

Where does rainfall stand? (as at 05/10/2026)

In the commune: no significant rain for 26 days. Rainfall over the last 30 days: 3 mm, against roughly 59 mm expected at this time of year – a 95% deficit.

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

Weekly drought update (as at 12/10/2026)

In the commune: recent rain (5 days ago). Rainfall over the last 30 days: 19 mm, against roughly 69 mm expected at this time of year – a 72% deficit.

A sustained deficit over this window, especially during the growing season, often precedes by a few weeks the drop in the water table visible 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: no significant rain for 12 days. Rainfall over the last 30 days: 19 mm, against roughly 80 mm expected at this time of year – a 76% deficit.

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

When was the water table last this low?

The reference piezometric station for the area (002FFSZ) has been monitoring the water table since 1997 – 30 years of records. As at 26/09/2026, the average level over the last thirty days is 70.81 m NGF (NGF, the French ordnance datum). Across the entire record, the water table has spent only 24.0% of its time below this level: a low level, in the lower quartile of known values.

• Last comparable episode: 30/10/2023 – 2.9 years ago
• Frequency: 19 similar episodes recorded since 1997, i.e. a return period of once every 2 years on average – in hydrologists’ terms, an intermediate episode
• Historical minimum: 65.58 m NGF, reached on 24/10/2022

This long memory changes how the risk should be read: a low level is not just a passing 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 further 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.