Mandelieu-la-Napoule: Clay Soil, Subsidence and Cracks – Official Data

Mandelieu-la-Napoule: is my cracked house linked to drought and clay?

Yes, it is likely if your cracks date from after a dry summer: the GASPAR database lists 1 drought decree (full list below) and 21 flood decrees in the commune, i.e. 22 natural disaster (Cat Nat) decrees. Local rainfall fits the classic pattern: four years below average (2020, 2021, 2022, 2023), then 2024 jumps sharply back to 1,215 mm (+47%) – exactly the kind of shock that puts foundations to work between the Siagne and the Esterel massif.

We are the independent building survey practice (Cassini Expertise), and we handle cracks and drought-related damage in Mandelieu-la-Napoule and across the whole department. This page brings together the official data for the commune to help you work out whether your cracks are serious, and what to do next.

Which natural disaster decrees cover Mandelieu-la-Napoule?

According to GASPAR (the database of decrees published in the Journal officiel since 1982), the commune has recorded a total of 22 natural disaster (Cat Nat) decrees:

• 1 drought decree (differential ground movement caused by clay shrink-swell (RGA – retrait-gonflement des argiles))
  • event dated 01/07/2022 (decree of 03/04/2023)
• 21 decrees relating to floods and storms

What to take from this: each drought decree covers a precise period. If your cracks appeared during this window, first check the exact date on your municipal decree, then two doors open: the declaration for Cat Nat compensation (if you declared within the deadlines), or failing that an action against the seller for hidden defect (vice caché) or fraudulent concealment (dol). Keep every dated document (photos, quotes, invoices): it is what will make it possible to prove the link with the covered period.

Is my plot in a clay risk zone?

The GéoRisques platform (BRGM) classifies Mandelieu-la-Napoule as high exposure to clay shrink-swell, with some sectors at medium exposure. This is the level insurers and notaires check before covering or selling a plot – you can run the same check free of charge on georisques.gouv.fr by entering your address. Note also: radon potential of class 3 in the commune (IRSN/GéoRisques data), a point to watch if you spend time in a basement or a closed-in ground floor.

This zoning completes the decree record above: the hazard level tells you what can happen, the decrees tell you what has already happened. 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 appear.

Mandelieu-la-Napoule: 22 Cat Nat decrees since 1982, in chronological order

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

• 🔴 07/2022 → 12/2022 – Drought (RGA – clay shrink-swell) (decree of 03/04/2023)

How an expert reads this: 1 drought and 21 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.

Mandelieu-la-Napoule: 22 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)
• 🔵 10/1987 → 10/1987 – Floods (decree of 02/12/1987)
• 🔵 10/1993 → 10/1993 – Floods (decree of 19/10/1993)
• 🔵 11/1994 → 11/1994 – Floods (decree of 21/11/1994)
• 🔵 01/1996 → 01/1996 – Floods (decree of 02/02/1996)
• 🔵 11/1997 → 11/1997 – Floods (decree of 02/02/1998)
• 🔵 12/1997 → 12/1997 – Floods (decree of 26/05/1998)
• 🔵 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 03/04/2001)
• 🔵 09/2005 → 09/2005 – Floods (decree of 10/10/2005)
• 🔵 12/2006 – Floods (decree of 03/07/2007)
• 🔵 09/2009 → 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)
• 🔵 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)
• 🔴 07/2022 → 12/2022 – Drought (RGA – clay shrink-swell) (decree of 03/04/2023)
• 🔵 10/2024 → 10/2024 – Floods (decree of 30/10/2024)

How an expert reads this: 1 drought and 21 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.

Mandelieu-la-Napoule: 22 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)
• 🔵 10/1987 → 10/1987 – Floods (decree of 02/12/1987)
• 🔵 10/1993 → 10/1993 – Floods (decree of 19/10/1993)
• 🔵 11/1994 → 11/1994 – Floods (decree of 21/11/1994)
• 🔵 01/1996 → 01/1996 – Floods (decree of 02/02/1996)
• 🔵 11/1997 → 11/1997 – Floods (decree of 02/02/1998)
• 🔵 12/1997 → 12/1997 – Floods (decree of 26/05/1998)
• 🔵 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 03/04/2001)
• 🔵 09/2005 → 09/2005 – Floods (decree of 10/10/2005)
• 🔵 12/2006 – Floods (decree of 03/07/2007)
• 🔵 09/2009 → 09/2009 – Floods (decree of 10/11/2009)
• 🔵 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)
• 🔵 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)
• 🔴 07/2022 → 12/2022 – Drought (RGA – clay shrink-swell) (decree of 03/04/2023)
• 🔵 10/2024 → 10/2024 – Floods (decree of 30/10/2024)

How an expert reads this: 1 drought and 21 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 Mandelieu-la-Napoule 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.

Forty years of decrees: the complete timeline of Mandelieu-la-Napoule

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)
• 🔵 10/1987 → 10/1987 – Floods (decree of 02/12/1987)
• 🔵 10/1993 → 10/1993 – Floods (decree of 19/10/1993)
• 🔵 11/1994 → 11/1994 – Floods (decree of 21/11/1994)
• 🔵 01/1996 → 01/1996 – Floods (decree of 02/02/1996)
• 🔵 11/1997 → 11/1997 – Floods (decree of 02/02/1998)
• 🔵 12/1997 → 12/1997 – Floods (decree of 26/05/1998)
• 🔵 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 03/04/2001)
• 🔵 09/2005 → 09/2005 – Floods (decree of 10/10/2005)
• 🔵 12/2006 – Floods (decree of 03/07/2007)
• 🔵 09/2009 → 09/2009 – Floods (decree of 10/11/2009)
• 🔵 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)
• 🔵 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)
• 🔴 07/2022 → 12/2022 – Drought (RGA – clay shrink-swell) (decree of 03/04/2023)
• 🔵 10/2024 → 10/2024 – Floods (decree of 30/10/2024)

How an expert reads this: 1 drought and 21 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 does local weather move the ground under my house?

Annual rainfall measured on the Mandelieu-la-Napoule weather grid (Open-Meteo data):

• 2019: 1,099 mm · 2020: 685 mm · 2021: 625 mm · 2022: 635 mm · 2023: 700 mm · 2024: 1,215 mm
• Average over the period: 826 mm/year, record drought year: 2021 (625 mm)
• Four years below the normals (2020-2023): 685, 625, 635 then 700 mm
• Then a surge in 2024 with 1,215 mm, i.e. +47%

In practice, the phenomenon plays out in two acts: the drought dries the clay at depth, it shrinks and the first cracks appear; then the rain returns in force, the ground rehydrates and swells again, causing differential movement. If your house dates from 1970-2000 and rests on shallow foundations, it takes the first damage – with a 12 to 24-month lag between the climate event and the appearance of the cracks. So identify the dry summers of the last two to three years to date the likely origin of your damage.

How can I tell whether the ground under my house has really moved?

The piezometric station for the area (ADES/Hubeau network, regular measurements) gives a more reliable indicator than any gut feeling: the average summer water table level, in metres NGF (the French ordnance datum):

• summer 2021: 151.47 m
• summer 2022: 140.24 m
• summer 2023: 125.73 m
• summer 2024: 147.77 m
• summer 2025: 154.6 m

The trend speaks for itself: the water table fell by almost 25.74 m between summer 2021 and summer 2023, then rose back above its starting level (154.6 m in the last known summer). This back-and-forth sums up clay shrink-swell: the clay ground shrinks when the water table drops, then swells again when it rises. Your foundations do not follow these movements as quickly – hence cracks appearing 12 to 24 months after dry summers. If you saw cracks forming in 2023-2024, this table explains why.

What 35 years of local rainfall tell us

Weather archives for the area cover 35 complete years (1991-2025). The driest ever recorded: 2007, with 398 mm of rain over the year, against a local average of 835 mm. 2022 ranks as the 9th driest year out of 35 (635 mm vs an 835 mm average); 2023 follows in 13th place (700 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 Mandelieu-la-Napoule

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 your home in Mandelieu-la-Napoule. Before calling a treatment contractor who will offer you resin injections or a ventilation system, our message is clear: not so fast. A wrong diagnosis leads to pointless, sometimes costly works that solve nothing.

The 4 causes and how to recognise them

• Rising damp: marks at the base of walls, up to 1 metre high, often with salt efflorescence, in older buildings with no waterproof barrier.
• Water ingress: marks linked to rain, often near a roof, a terrace, a balcony or a façade exposed to sea spray, common along the Mandelieu-la-Napoule coastline.
• Condensation: diffuse tide marks, mould in cold corners, poorly ventilated bathrooms or kitchens, worse in winter.
• Leak: a localised, evolving mark, often near a pipe, a shower room or a service duct.

The trap of the diagnosis sold by the treatment contractor

Many companies selling damp treatments carry out the diagnosis themselves. The conflict of interest is obvious: the heavier the proposed treatment, the higher the invoice. As a result, resin gets injected into walls that were simply victims of roof ingress, or a costly ventilation system is installed when a façade crack was enough to explain the problem. An independent diagnosis, with no associated works to sell, identifies the true cause before any money is committed.

Before any treatment, request an independent damp survey in Mandelieu-la-Napoule. To dig deeper into causes and solutions, read our damp guide for the 06, 83 and 13.

Which crack signs should push you to act in Mandelieu-la-Napoule?

• 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 over time: fit a tell-tale (plaster or gauge) and take a dated photo every month
• Doors and windows that stick, floor tiles splitting diagonally, render that comes away or bulges
• A house on clay ground, trees close by, defective drainage

With its single recognised drought decree, Mandelieu-la-Napoule remains exposed: as soon as several of these signs build up, do not fill the crack yourself and do not paint over it – get a survey before any repair, and before signing a purchase or a sale.

Buying or selling a cracked house here: what are my rights?

With the recent drought decrees and the volume of transactions under way, plenty of properties change owner without the damage being mentioned. If you are the buyer and discover cracks after the sale, you have two routes:

• Hidden defect (vice caché, Article 1641 of the French Civil Code): serious cracks, not visible at the viewing, predating the sale → price reduction or cancellation, 2-year time limit from 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

Before starting proceedings, have the cracks dated and characterised by an independent expert: it is this report that will give weight to your file with a French property lawyer.

What happens during a drought/clay survey in Mandelieu-la-Napoule?

• 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 (1 drought decree), 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 Mandelieu-la-Napoule.

We are an independent expert with no ties whatsoever to a repair company – our only role is to record and to cost, not to sell works. Request a visit in Mandelieu-la-Napoule – also read 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 Mandelieu-la-Napoule (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: Mandelieu-la-Napoule 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 Mandelieu-la-Napoule (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: Mandelieu-la-Napoule 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 Mandelieu-la-Napoule (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: Mandelieu-la-Napoule 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 Mandelieu-la-Napoule (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: Mandelieu-la-Napoule 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 Mandelieu-la-Napoule in a clay risk zone?

Yes. The Alpes-Maritimes is very widely affected by clay shrink-swell, as the BRGM mapping on georisques.gouv.fr shows. In Mandelieu-la-Napoule, the drought decree recognised in GASPAR confirms that this risk is anything but theoretical: check your exact address on the map before buying or starting foundation works.

Can a cracked house here be compensated under natural disaster provisions?

Only if your damage falls within a period covered by a decree (the last recognised one covers 2023) and if you declared the claim to your insurer within 30 days of the decree. Otherwise, the action against the seller remains – and there, precisely dating the damage by survey becomes decisive for your file.

Where do these figures come from, and can I check them myself?

Yes: the decrees come from GASPAR (Journal officiel, open data, updated 2025), and the rainfall figures from the Open-Meteo weather archives for the Mandelieu-la-Napoule grid. We simply reproduce them, without altering them – you can cross-check every figure on the source websites.

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

In the commune: recent rain (3 days ago). Rainfall over the last 30 days: 5 mm, against roughly 57 mm expected at this time of year – a 91% 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: 5 mm, against roughly 59 mm expected at this time of year – a 92% 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 (4 days ago). Rainfall over the last 30 days: 74 mm, against roughly 69 mm expected at this time of year – a 7% 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.

Weekly drought update (as at 19/10/2026)

In the commune: recent rain (1 day ago). Rainfall over the last 30 days: 82 mm, against roughly 80 mm expected at this time of year – a 2% 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.

The water table against its historical record: what 22 years of measurements show

The reference piezometric station for the area (002HDRP) has been monitoring the water table since 2005 – 22 years of records. As at 02/10/2026, the average level over the last thirty days is 149.08 m NGF (NGF, the French ordnance datum). Across the entire record, the water table has spent only 29.6% of its time below this level: a low level, in the lower quartile of known values.

• Last comparable episode: 03/10/2024 – 2.0 years ago
• Frequency: 10 similar episodes recorded since 2005, i.e. a return period of once every 2 years on average – in hydrologists’ terms, an intermediate episode
• Historical minimum: 123.4 m NGF, reached on 08/10/2023

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.