Aix-en-Provence: Clay Soil, Subsidence and Cracks – Official Data

The geological and climate context of Aix-en-Provence

If your house in Aix-en-Provence is cracking after a dry summer, it is probably no coincidence: the commune has 14 drought decrees recognised since 1993 (including 2020, 2023 and 2024) and 14 flood decrees, i.e. 28 Cat Nat decrees in total. The local weather matches the scenario: three dry years in a row (2020, 2022, 2023), then 2024 bouncing back to 846 mm (+30%) – precisely the dry/wet alternation that puts foundations to work in the city of a thousand fountains. If your cracks date from this period, keep dated photographs: they are the piece that opens the door to compensation.

Cassini Expertise, an independent building expert, handles drought-related cracks and damage in Aix-en-Provence and across the whole of the 13. This page brings together the commune’s official data, with no commercial angle, to help you work out whether your case is documented and what to do next.

Aix-en-Provence: drought, clay and cracks – what the official data says

The GASPAR database (decrees published in the Official Gazette since 1982) lists 28 natural disaster decrees for the commune of Aix-en-Provence:

• 14 drought decrees (differential ground movement linked to clay shrink-swell)
  • event of 01/05/1989 (decree of 18/05/1993)
  • event of 01/01/1992 (decree of 30/06/1994)
  • event of 01/01/1993 (decree of 27/12/2000)
  • event of 01/01/1998 (decree of 27/12/2000)
  • event of 01/01/2002 (decree of 11/01/2005)
  • event of 01/01/2005 (decree of 20/02/2008)
  • event of 01/01/2006 (decree of 18/04/2008)
  • event of 01/01/2007 (decree of 07/08/2008)
  • event of 01/07/2007 (decree of 07/08/2008)
  • event of 01/04/2016 (decree of 25/07/2017)
  • event of 01/01/2017 (decree of 10/07/2018)
  • event of 01/04/2019 (decree of 29/04/2020)
  • event of 01/04/2022 (decree of 03/04/2023)
  • event of 01/04/2023 (decree of 18/06/2024)
• 14 flood and storm decrees

What to take from it in practical terms: if your cracks appeared during one of the periods listed above, you can claim Cat Nat compensation – provided you declared the claim to your insurer within 30 days of the decree. If that deadline has passed, or nobody declared at the time (a frequent case with a previous owner), the route of a claim against the seller, for hidden defect or fraudulent concealment, remains.

What the official clay mapping says

The GéoRisques platform (BRGM) classifies Aix-en-Provence at high exposure to clay shrink-swell, with some sectors at medium exposure. This is the level insurers and notaires already consult to assess the risk on a plot – you can check the exact address of your property free of charge on georisques.gouv.fr before any purchase. Note also: radon potential of class 2 in the commune (IRSN/GéoRisques data), a point to watch if you are renovating or insulating a basement.

This ranking complements the decree history above: the hazard 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 – a signal to factor in before making an offer.

What characterises Aix-en-Provence from a building surveying perspective

In Aix-en-Provence, the surveyor works across a contrasted territory that runs from the foothills of the Sainte-Victoire and the slopes of the Montaiguet to the plain of the Arc, by way of the hills of the Jas de Bouffan and Puyricard: this topographical diversity produces highly heterogeneous soils, often clayey or marly-limestone, that react strongly to wetting and drying cycles. The building stock mixes an old centre with sometimes rudimentary foundations, renovated bastides and Provençal farmhouses, and a belt of detached houses from the great estates of the 1970s-90s that spread over former clayey farmland, on shallow foundations lightly reinforced for this type of ground. The abundant pines and oaks, planted or kept for shade in these estates, make matters worse: their roots pump water from the soil next to the houses and compound the shrinkage of the clay in dry periods, causing differential settlements well known to local professionals. We are regularly called to villas of this generation where façade cracks appear after several dry summers in a row, the clay ground contracting then swelling again with the rains, creating repeated movements that eventually tire foundations never designed to absorb this kind of stress.

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

The weather archives for the area cover 35 complete years (1991-2025). The driest ever recorded: 2007, with 428 mm over the year, against a local average of 669 mm. 2022 ranks as the 7th driest year out of 35 (482 mm against an average of 669 mm); 2023 follows in 12th place (552 mm).

This ranking gives the true measure of the recent sequence: when the years 2020-2023 crowd into the top of the drought table, the clay has not had time to rehydrate between episodes – the classic scenario for delayed cracks. The reverse is just as instructive: a very wet year following an exceptional drought causes abrupt swelling of the ground.

Aix-en-Provence: 28 Cat Nat decrees since 1982, in chronological order

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

• 🔵 11/1982 → 11/1982 – Cyclones / Storms (decree of 18/11/1982)
• 🔵 11/1982 → 11/1982 – Floods (decree of 18/11/1982)
• 🔵 08/1986 → 08/1986 – Floods (decree of 11/12/1986)
• 🔴 05/1989 → 12/1991 – Drought (RGA – clay shrink-swell) (decree of 18/05/1993)
• 🔴 01/1992 → 02/1993 – Drought (RGA – clay shrink-swell) (decree of 30/06/1994)
• 🔴 01/1993 → 06/1993 – Drought (RGA – clay shrink-swell) (decree of 27/12/2000)
• 🔵 09/1993 → 09/1993 – Floods (decree of 11/10/1993)
• 🔵 01/1994 → 01/1994 – Floods (decree of 26/01/1994)
• 🔵 11/1994 → 11/1994 – Floods (decree of 21/11/1994)
• 🔴 01/1998 → 06/1998 – Drought (RGA – clay shrink-swell) (decree of 27/12/2000)
• 🔵 09/1998 – Floods (decree of 29/12/1998)
• 🔴 01/2002 → 06/2002 – Drought (RGA – clay shrink-swell) (decree of 11/01/2005)
• 🔵 12/2003 → 12/2003 – Floods (decree of 12/12/2003)
• 🔴 01/2005 → 03/2005 – Drought (RGA – clay shrink-swell) (decree of 20/02/2008)
• 🔵 09/2005 – Floods (decree of 10/10/2005)
• 🔴 01/2006 → 03/2006 – Drought (RGA – clay shrink-swell) (decree of 18/04/2008)
• 🔴 01/2007 → 03/2007 – Drought (RGA – clay shrink-swell) (decree of 07/08/2008)
• 🔴 07/2007 → 09/2007 – Drought (RGA – clay shrink-swell) (decree of 07/08/2008)
• 🔵 12/2008 → 12/2008 – Floods (decree of 17/04/2009)
• 🔴 04/2016 → 09/2016 – Drought (RGA – clay shrink-swell) (decree of 25/07/2017)
• 🔴 01/2017 → 12/2017 – Drought (RGA – clay shrink-swell) (decree of 10/07/2018)
• 🔴 04/2019 → 06/2019 – Drought (RGA – clay shrink-swell) (decree of 29/04/2020)
• 🔵 12/2019 – Floods (decree of 02/03/2020)
• 🔵 10/2021 → 10/2021 – Floods (decree of 15/10/2021)
• 🔴 04/2022 → 09/2022 – Drought (RGA – clay shrink-swell) (decree of 03/04/2023)
• 🔵 11/2022 – Floods (decree of 16/01/2023)
• 🔴 04/2023 → 06/2023 – Drought (RGA – clay shrink-swell) (decree of 18/06/2024)
• 🔵 06/2023 → 06/2023 – Floods (decree of 18/12/2023)

How an expert reads this: 14 droughts and 14 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 Aix-en-Provence

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 blistering render in Aix-en-Provence. Before signing anything, you need to know that most companies selling treatments (resin injections, drainage) are selling a product, not a diagnosis – and their conclusion will suit their catalogue.

The four causes and how to recognise them

• Rising damp: groundwater climbs into the walls by capillary action. A stain that starts at the base and rises in an irregular horizontal line, often with saltpetre, typical of older buildings.
• Water ingress: water penetrates from outside (roof, cracked façade, gutter). A localised stain, often near a weak point, that worsens after rain.
• Condensation: humid indoor air condenses on cold walls. Mould in room corners, around windows, made worse by poor ventilation.
• Leak: a defective pipe, drain or roof terrace. A pinpoint stain, sometimes unrelated to the weather, that can appear suddenly.

The trap of the diagnosis sold by the treatment contractor

In Aix-en-Provence as elsewhere, many companies that bill the treatment are also the ones making the diagnosis. The outcome is predictable: they almost always find rising damp, because that is the service they sell (resin injection, drainage). Yet in a large share of the cases seen on the ground, the real cause is simple condensation or a one-off water ingress, which can be fixed for a fraction of the price.

Before committing to works, have an independent diagnosis carried out in Aix-en-Provence by an expert who sells no treatment. You will also find a detailed explanation of causes and solutions in our damp guide for the 06, 83 and 13.

Why do cracks appear several months after the drought?

Annual rainfall measured on the Aix-en-Provence weather grid (Open-Meteo data):

• 2019: 761 mm · 2020: 481 mm · 2021: 778 mm · 2022: 482 mm · 2023: 552 mm · 2024: 846 mm
• Average over the period: 650 mm/year, driest year: 2020 (481 mm)
• Three years below average: 481 mm in 2020, 482 mm in 2022, 552 mm in 2023
• Then a rebound to 846 mm in 2024

Clay shrink-swell plays out in two stages, and that is what misleads owners. The drought dries the clay at depth, it shrinks, and the first cracks appear. Then the rain returns, the ground rehydrates abruptly and swells in turn, triggering differential movements. Houses on shallow foundations – the majority of villas built between 1970 and 2000 – absorb the first damage, often 12 to 24 months after the dry episode. If you see a crack today, think back two summers to find its origin.

Should a crack in Aix-en-Provence worry me?

• A stair-step crack, passing through the wall, open by more than 2 mm: report it without delay
• A crack that is evolving over time: fit a tell-tale (a plaster band or a marker pen spot) and check it after a few months
• Disorders that often go together: doors and windows that stick, floor tiles splitting diagonally, render that bulges – note them, they strengthen the diagnosis
• Clay ground, trees close to the house, a drain in poor condition: aggravating factors to check around the property

With 14 drought decrees already recognised for the commune, a cluster of several of these signals justifies a survey before any repair – and before any buying or selling decision. Do not fill a crack in before having it recorded: once filled, it is no longer evidence.

Buying or selling a cracked house in Aix-en-Provence: what are my rights?

Between the recent drought decrees and the volume of transactions under way, quite a few properties change hands with damage passed over in silence. If you discover cracks after signing, two legal levers are available to you:

• Hidden defect (vice caché, Article 1641 of the French Civil Code): serious cracks, not visible at a viewing, predating the sale → price reduction or cancellation of the sale
• Fraudulent concealment (dol, Article 1137): the seller knew about the damage and hid it → cancellation plus damages, within 5 years; the commune’s GASPAR decree then strengthens your file

On this legal side, instruct a French property lawyer.

What actually happens during a drought/clay survey in Aix-en-Provence?

• Technical visit: crack mapping and classification, width measurements, associated functional disorders
• Context analysis: clay zoning, the commune’s Cat Nat history (14 drought decrees), local drought episodes
• Costing of repair works: underpinning, injections, drainage – with several scenarios
• A written report your insurer or lawyer can use directly

Independent expert, with no ties whatsoever to a works company. Request a visit in Aix-en-Provence – see also our complete guide to RGA and Cat Nat in the 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 requirement, introduced by the ELAN law no. 2018-1021, article 68 (decree no. 2019-495 of 22 May 2019), applies to Aix-en-Provence (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: Aix-en-Provence 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 Aix-en-Provence in a clay risk zone?

The Bouches-du-Rhône is very largely covered by the clay shrink-swell hazard (BRGM mapping, consultable on georisques.gouv.fr). In Aix-en-Provence, the 14 drought decrees recorded in GASPAR show this is not a theoretical risk but an established fact in the commune: if your property sits in a high-exposure sector, it is a point to monitor actively, not an administrative footnote to ignore.

Can a cracked house in Aix-en-Provence be covered under natural disaster provisions?

Only if the damage is dated from a period covered by a decree (the last recognised: 1993, 1994, 2000, 2005, 2008, 2017, 2018, 2020, 2023, 2024) and if the claim was declared within 30 days. Failing that, the route of a claim against the seller remains – and precisely dating the damage through a survey then becomes the crux of the file, because that date determines whether you plead hidden defect or fraudulent concealment.

Can the data presented on this page be verified?

Yes. The decrees come from the GASPAR database (Official Gazette, open data sets, 2025 update), the rainfall from the Open-Meteo weather archives for the Aix-en-Provence grid. Cassini Expertise does not adjust these figures.

What is the rainfall situation? (as at 05/10/2026)

In the commune: recent rain (4 days ago). Rainfall over the last 30 days: 23 mm, against roughly 56 mm expected at this time of year – a 59% deficit.

A sustained deficit over this window, especially in 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 12/10/2026)

In the commune: recent rain (5 days ago). Rainfall over the last 30 days: 26 mm, against roughly 61 mm expected at this time of year – a 57% deficit.

A sustained deficit over this window, especially in 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 notable rain for 12 days. Rainfall over the last 30 days: 26 mm, against roughly 66 mm expected at this time of year – a 61% deficit.

A sustained deficit over this window, especially in 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: 29 years of measurements, a well-documented context

The reference piezometric station for the sector (002JNGC) has been monitoring the water table since 1998 – 29 years of records. As at 02/10/2026, the mean level over the last thirty days is 211.61 m NGF. Across the whole record, the water table has spent only 15.1% of its time below this level: a very low level, rarely reached in the station’s record.

• Last comparable episode: 03/10/2024 – 2.0 years ago
• Frequency: 64 similar episodes recorded since 1998, i.e. a return every year on average – in hydrologists’ language, a rare event
• Historical minimum: 210.96 m NGF, reached on 05/08/2017

This long memory changes how the risk is read: a low level is not merely a weather episode, it is an event whose frequency is known. For a house on clay, it is that frequency that informs the probability of further settlement – and hence the urgency of precautions.

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.