Menton: Clay Soil, Subsidence and Cracks – Official Data

Soil and building specifics in Menton

In Menton, this mosaic of hills plunging towards the Mediterranean – from Le Borrigo to old Menton by way of the Garavan and Monti districts – concentrates highly heterogeneous ground, typical of the steep relief of the Alpes-Maritimes. We regularly record cracks there on 1970s-80s villas built on restanques (retaining terraces), these backfilled platforms created to gain living space on clayey slopes, often with shallow foundations poorly suited to the gradient. The older Provençal stock of the historic centre suffers differently, with stone walls and footings never designed to absorb the movement of swelling soils. The Mediterranean vegetation – umbrella pines, olive trees and above all the tall eucalyptus and citrus trees of the exotic gardens so characteristic of the area – makes things worse by locally drying out the clays during summer drought, creating marked differential settlement between the shaded and sunlit parts of the same plot. The more recent estates, developed on the heights from the 1990s onwards to make the most of the bay views, often rest on imported fill whose bearing capacity remains uneven. We also see that the many heavy renovations of old bastides, with extensions and pools added onto the original building, create breaking points between structures of different ages, particularly sensitive to the shrink-swell cycles of the local clay.

Drought in the rear-view mirror: 35 years of measured rainfall

Weather archives for the area cover 35 complete years (1991-2025). The driest ever recorded: 2007, with 451 mm of rain over the year, against a local average of 820 mm. 2022 ranks as the 2nd driest year out of 35 (451 mm vs an 820 mm average); 2023 follows in 7th place (604 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.

Damp, water ingress and rising damp in Menton

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 Menton and you may already have read that you need resin injections or mechanical ventilation. Wait before signing anything: treating the wrong cause solves nothing, and the wall will start degrading again a few months later.

The 4 causes and how to recognise them

• Rising damp: ground water climbs into the walls by capillary action. A tide mark stopping at a constant height (often 1 to 1.5 m), whitish salts on the surface, a damp wall base even in summer. Frequent in the older buildings of Menton with no waterproof barrier.
• Water ingress: water enters through a façade, a roof terrace or a defective joint. Marks that appear mostly after rain, localised near a window, a balcony or a weather-exposed wall.
• Condensation: moist air condenses on cold surfaces, often in a poorly ventilated room (bathroom, kitchen). Misted windows, mould in ceiling corners, a stale smell.
• Leak: a defective pipe or drain. A localised mark, sometimes with swelling of the finish, independent of the weather or the season.

The trap of the diagnosis sold by the treatment contractor

Many resin injection companies offer a “free quote” that systematically concludes rising damp, even when the real cause is water ingress or condensation. Commercial logic: that is precisely the treatment they sell. The outcome for the owner in Menton: several thousand euros spent, and the damp returning because the origin was never treated.

An independent diagnosis, with no commercial interest in selling a treatment, identifies the real cause before any spending. Request an independent survey in Menton to know exactly what you are dealing with. To go further, read our damp guide for the 06, 83 and 13.

Menton: drought, clay and cracks – what the official record says

Your house in Menton is cracking and you want to know whether drought is to blame? The GASPAR database lists for the commune 2 drought decrees (full list below) and 16 flood decrees, i.e. 18 natural disaster (Cat Nat) decrees. Local weather records confirm the scenario: three years below average (2021, 2022, 2023), then a jump to 1,221 mm in 2024 (+60%) – exactly the mechanism that cracks foundations on the Coast.

Cassini Expertise, an independent building expert, diagnoses cracks and drought-related damage in Menton and throughout the 06. This page brings together the commune’s official figures to help you work out whether your cracks are linked to a recognised event – and what to do next.

How many natural disaster decrees in Menton? The official record

The GASPAR database (decrees published in the Journal officiel since 1982) lists, for Menton, 18 natural disaster decrees:

• 2 drought decrees (differential ground movement linked to clay shrink-swell (RGA – retrait-gonflement des argiles))
  • event of 01/01/2022 (decree of 19/09/2023)
  • event of 31/03/2023 (decree of 23/09/2024)
• 16 flood decrees and storm

What to do with this: if your cracks appeared during one of these two periods, you can claim Cat Nat compensation, provided the claim was declared within 30 days of the decree. If you missed that deadline, or the damage predates your purchase, keep these dates carefully: they will serve to date the disorder for a claim against the seller (hidden defect – vice caché – or fraudulent concealment – dol, see below).

Is Menton in a clay risk zone? The official rating (GéoRisques/BRGM)

The GéoRisques platform (BRGM) classifies Menton as high exposure to clay shrink-swell, with some sectors at medium exposure. This is the level insurers and notaires check before assessing the risk on a plot – you can run the same check yourself on georisques.gouv.fr by typing in your address.

This zoning completes the decree record above: the hazard level tells you what can happen on your plot, the decrees tell you what has already happened at commune level. If your house is in a high exposure area and has been through one or more dry summers, take cracks seriously as soon as they go beyond the cosmetic stage.

Menton: 18 Cat Nat decrees since 1982, in chronological order

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

• 🔴 01/2022 → 12/2022 – Drought (RGA – clay shrink-swell) (decree of 19/09/2023)
• 🔴 03/2023 → 09/2023 – Drought (RGA – clay shrink-swell) (decree of 23/09/2024)

How an expert reads this: 2 droughts and 16 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.

Menton: 18 Cat Nat decrees since 1982, in chronological order

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)
• 🔵 11/1982 → 11/1982 – Floods (decree of 04/02/1983)
• 🔵 09/1991 → 09/1991 – Floods (decree of 21/09/1992)
• 🔵 10/1992 → 10/1992 – Floods (decree of 04/02/1993)
• 🔵 09/1993 → 09/1993 – Floods (decree of 19/10/1993)
• 🔵 02/1994 → 02/1994 – Floods (decree of 12/04/1994)
• 🔵 09/1995 – Floods (decree of 03/04/1996)
• 🔵 09/1998 – Floods (decree of 21/01/1999)
• 🔵 10/1999 → 10/1999 – Floods (decree of 03/03/2000)
• 🔵 10/2000 – Floods (decree of 19/12/2000)
• 🔵 11/2000 → 11/2000 – Floods (decree of 19/12/2000)
• 🔵 09/2005 → 09/2005 – Floods (decree of 10/10/2005)
• 🔵 12/2013 → 12/2013 – Floods (decree of 22/04/2014)
• 🔵 01/2014 → 01/2014 – Floods (decree of 31/01/2014)
• 🔵 11/2019 → 11/2019 – Floods (decree of 28/11/2019)
• 🔵 12/2019 – Floods (decree of 02/03/2020)
• 🔴 01/2022 → 12/2022 – Drought (RGA – clay shrink-swell) (decree of 19/09/2023)
• 🔴 03/2023 → 09/2023 – Drought (RGA – clay shrink-swell) (decree of 23/09/2024)

How an expert reads this: 2 droughts and 16 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.

Menton: 18 Cat Nat decrees since 1982, in chronological order

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)
• 🔵 11/1982 → 11/1982 – Floods (decree of 04/02/1983)
• 🔵 09/1991 → 09/1991 – Floods (decree of 21/09/1992)
• 🔵 10/1992 → 10/1992 – Floods (decree of 04/02/1993)
• 🔵 09/1993 → 09/1993 – Floods (decree of 19/10/1993)
• 🔵 02/1994 → 02/1994 – Floods (decree of 12/04/1994)
• 🔵 09/1995 – Floods (decree of 03/04/1996)
• 🔵 09/1998 – Floods (decree of 21/01/1999)
• 🔵 10/1999 → 10/1999 – Floods (decree of 03/03/2000)
• 🔵 10/2000 – Floods (decree of 19/12/2000)
• 🔵 11/2000 → 11/2000 – Floods (decree of 19/12/2000)
• 🔵 09/2005 → 09/2005 – Floods (decree of 10/10/2005)
• 🔵 12/2013 → 12/2013 – Floods (decree of 22/04/2014)
• 🔵 01/2014 → 01/2014 – Floods (decree of 31/01/2014)
• 🔵 11/2019 → 11/2019 – Floods (decree of 28/11/2019)
• 🔵 12/2019 – Floods (decree of 02/03/2020)
• 🔴 01/2022 → 12/2022 – Drought (RGA – clay shrink-swell) (decree of 19/09/2023)
• 🔴 03/2023 → 09/2023 – Drought (RGA – clay shrink-swell) (decree of 23/09/2024)

How an expert reads this: 2 droughts and 16 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.

The official clay shrink-swell exposure rating

The GéoRisques platform (BRGM) classifies Menton 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.

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.

Forty years of decrees: Menton’s complete timeline

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)
• 🔵 11/1982 → 11/1982 – Floods (decree of 04/02/1983)
• 🔵 09/1991 → 09/1991 – Floods (decree of 21/09/1992)
• 🔵 10/1992 → 10/1992 – Floods (decree of 04/02/1993)
• 🔵 09/1993 → 09/1993 – Floods (decree of 19/10/1993)
• 🔵 02/1994 → 02/1994 – Floods (decree of 12/04/1994)
• 🔵 09/1995 – Floods (decree of 03/04/1996)
• 🔵 09/1998 – Floods (decree of 21/01/1999)
• 🔵 10/1999 → 10/1999 – Floods (decree of 03/03/2000)
• 🔵 10/2000 – Floods (decree of 19/12/2000)
• 🔵 11/2000 → 11/2000 – Floods (decree of 19/12/2000)
• 🔵 09/2005 → 09/2005 – Floods (decree of 10/10/2005)
• 🔵 12/2013 → 12/2013 – Floods (decree of 22/04/2014)
• 🔵 01/2014 → 01/2014 – Floods (decree of 31/01/2014)
• 🔵 11/2019 → 11/2019 – Floods (decree of 28/11/2019)
• 🔵 12/2019 – Floods (decree of 02/03/2020)
• 🔴 01/2022 → 12/2022 – Drought (RGA – clay shrink-swell) (decree of 19/09/2023)
• 🔴 03/2023 → 09/2023 – Drought (RGA – clay shrink-swell) (decree of 23/09/2024)

How an expert reads this: 2 droughts and 16 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.

Why local weather triggers cracks in Menton

Annual rainfall measured on the Menton weather grid (Open-Meteo data):

• 2019: 1,029 mm · 2020: 711 mm · 2021: 573 mm · 2022: 450 mm · 2023: 604 mm · 2024: 1,221 mm
• Average over the period: 764 mm/year, driest year: 2022 (450 mm)
• Three deficit years in a row (2021, 2022, 2023): 573 mm, then 450 mm, then 604 mm
• Then 2024 jumps sharply back to 1,221 mm (+60%)

Clay shrink-swell plays out in two stages: first the drought dries the clay at depth (shrinkage, first cracks), then the return of the rain rehydrates the ground at once (swelling, differential movement). If your house was built between 1970 and 2000 on shallow foundations – as most villas in the area were – watch your cracks for 12 to 24 months after a dry episode: that is the typical appearance lag.

Where does rainfall stand? (as at 04/10/2026)

In the commune: recent rain (3 days ago). Rainfall over the last 30 days: 4 mm, against roughly 58 mm expected at this time of year – a 93% 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 05/10/2026)

In the commune: recent rain (4 days ago). Rainfall over the last 30 days: 4 mm, against roughly 58 mm expected at this time of year – a 93% 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.

Rainfall today: where do we stand? (as at 12/10/2026)

In the commune: recent rain (5 days ago). Rainfall over the last 30 days: 84 mm, against roughly 65 mm expected at this time of year – a 29% surplus.

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.

Rainfall today: where do we stand? (as at 19/10/2026)

In the commune: no significant rain for 12 days. Rainfall over the last 30 days: 84 mm, against roughly 72 mm expected at this time of year – a 17% surplus.

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.

Water table memory: 30 years of measurements, a well-documented context

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.

Cracks in Menton: the warning signs

• A stair-step crack, passing through the wall, more than 2 mm wide – measure it with a ruler or a gauge, do not trust your eye
• A crack that evolves: fit a plaster tell-tale or a marked reference point, and come back to measure a few months later
• Associated disorders to watch at the same time: doors and windows that stick, floor tiles splitting diagonally, render that bulges
• Aggravating factors on your plot: clay ground, a tree close to the façade, a defective gutter or drainage system

With the 2 drought decrees already recognised in Menton, a combination of several of these signs justifies a survey before any repair – and before any buying or selling decision. Do not have an active crack repointed or filled before an expert has measured and photographed it: you would be erasing the evidence.

Is my cracked house in Menton eligible for compensation, and what if the seller hid the cracks?

Between the recent drought decrees and the growing number of sales, plenty of properties change hands with damage passed over in silence. If you discover cracks after buying, you have two levers:

• Hidden defect (vice caché, Article 1641 of the French Civil Code): serious cracks, invisible at the viewing, predating the sale → you can claim a price reduction or cancellation of the sale, within 2 years from the day you discover the defect
• Fraudulent concealment (dol, Article 1137): the seller knew and concealed the damage → you can claim cancellation of the sale and damages, within 5 years; the commune’s GASPAR decree record then supports your file

Before starting proceedings, have the damage dated and costed by an independent expert: it is the piece that will convince your French property lawyer and, where applicable, the judge.

How a drought/clay survey works in Menton

• On-site technical visit: mapping and classification of every crack, precise width measurement, inventory of functional disorders (doors, windows, tiling)
• Context set against the data on this page: clay zoning, the commune’s Cat Nat record (2 drought decrees), local dry episodes
• Costing of the necessary works: underpinning, injections, drains – with several scenarios depending on severity
• A written report you can pass on as it stands to your insurer or your lawyer

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

Independent expert, with no ties to any repair company. Request a visit in Menton – see also our complete RGA and Cat Nat guide for 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 Menton (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: Menton 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.

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 Menton (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: Menton 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.

The soil survey requirement: what has changed since July 2026

Since 1 July 2026, any construction or extension on ground exposed to clay shrink-swell requires a preliminary geotechnical survey. This requirement, introduced by the Climate and Resilience law (article 88), applies particularly to Menton (high exposure under the BRGM classification).

• What it changes for building: a soil survey is no longer optional – 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 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: Menton 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.

The soil survey requirement: what has changed since July 2026

Since 1 July 2026, any construction or extension on ground exposed to clay shrink-swell requires a preliminary geotechnical survey. This requirement, introduced by the Climate and Resilience law (article 88), applies particularly to Menton (high exposure under the BRGM classification).

• What it changes for building: a soil survey is no longer optional – 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 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: Menton 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.

Frequently asked questions

Is Menton among the clay risk zones?

Yes. The Alpes-Maritimes is very widely covered by the clay shrink-swell hazard (BRGM mapping, freely consultable on georisques.gouv.fr by typing in your address). For Menton, the GASPAR record with its 2 recognised drought decrees confirms that the risk is anything but theoretical for your property.

Can a cracked house in Menton be covered under natural disaster provisions?

Only if your damage appeared during a period covered by a decree (the last two recognised periods: 2023, 2024) and if you duly declared the claim to your insurer within 30 days of the decree being published. If not, you still have the action against the seller – and there, precisely dating your damage by survey becomes the crux of the file.

Can the data on this page be checked independently?

Yes, and we encourage you to do so: the decrees come from the GASPAR database (Journal officiel, open data sets, updated 2025), and the rainfall figures from the Open-Meteo weather archives for the Menton grid. Cassini Expertise does not alter 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.