# Marseille: Clay Soil, Subsidence and Cracks – Official Data > Is your Marseille property at risk from clay soil? BRGM data, rainfall records, crack assessment. Independent expert, reports in English. - URL : https://cassini-expertise.fr/en/marseille-clay-subsidence-cracks/ - Langue : en-US - Mis Γ  jour : 2026-11-06 - Site : Cassini Expertise (https://cassini-expertise.fr/) ## The geological and climate context of [Marseille](https://cassini-expertise.fr/en/marseille-clay-subsidence-cracks/) ## Marseille - live drought update updated today 🟒 Normal conditions in Marseille Β· Last rain: - 30 days - mm normal: - mm 0% 0 mm 3 months - mm normal: - mm 0% 0 mm 6 months - mm normal: - mm 0% 0 mm 1 year - mm normal: - mm 0% 0 mm **How this score is calculated** 1️⃣ no ongoing drought β†’ 0.0 pt 2️⃣ medium clay exposure (BRGM) β†’ 1.0 pts 3️⃣ 0 recognized cat-nat decree β†’ 0.0 pts Risk level0/5 [Cracks on my house? β†’](https://cassini-expertise.fr/en/)[Free quote β†’](https://cassini-expertise.fr/en-contact/) πŸ–¨ Download the report Data: Open-Meteo/MΓ©tΓ©o-France Β· BRGM Β· IRSN Β· GASPAR Β· ADES Normales 1991-2025 Β· DonnΓ©es mΓ©tΓ©o updated every morning at 6 am (nappe : derniΓ¨re publication ADES) **If your house in Marseille has cracks and you are wondering whether drought is the cause: the GASPAR database lists 15 drought decrees (full list below) and 28 flood decrees, i.e. 43 Cat Nat decrees for the commune. Three years of markedly low rainfall (2020, 2022, 2023) on a city built between hills and clay quarters: exactly the terrain where foundations take the most strain. If your cracks appeared or worsened after a dry summer, the right reflex is to have them dated and classified by an expert before any repair or any sale.** Cassini Expertise, an independent building expert, handles drought-related cracks and damage in Marseille and across the whole of the 13. This page sets out the commune’s official data, with no sales talk. ## Marseille: drought, clay and cracks – what the official data says According to GASPAR (decrees published in the Official Gazette since 1982), Marseille has recorded a total of **43** natural disaster decrees. If your damage dates from one of these periods, keep a careful record of when the cracks appeared: that date will determine whether you can still open a compensation file. - **15 drought decrees** (differential ground movement linked to clay shrink-swell) - event of **01/05/1989** (decree of 25/01/1993) - event of **01/01/1992** (decree of 27/12/2000) - event of **01/01/1998** (decree of 27/12/2000) - event of **01/01/2002** (decree of 25/08/2004) - event of **01/01/2004** (decree of 11/06/2008) - event of **01/01/2005** (decree of 11/06/2008) - event of **01/01/2006** (decree of 11/06/2008) - event of **01/01/2007** (decree of 07/08/2008) - event of **01/07/2007** (decree of 07/08/2008) - event of **01/01/2008** (decree of 16/10/2009) - event of **01/07/2016** (decree of 25/07/2017) - event of **01/07/2017** (decree of 10/07/2018) - event of **01/07/2019** (decree of 28/07/2020) - event of **01/04/2022** (decree of 03/04/2023) - event of **01/04/2023** (decree of 18/06/2024) - **28 flood** and storm decrees Each drought decree covers a precise window of time: if your house’s damage falls within a recognised period, Cat Nat compensation becomes possible – provided you declared the claim to your insurer within 30 days of the decree being published. If that deadline has passed or the period is not covered, the route of a claim against the seller, for hidden defect or fraudulent concealment, remains: see below. ## What the official clay mapping says The GΓ©oRisques platform (BRGM) classifies Marseille at **high exposure** to clay shrink-swell, with sectors at high and medium exposure. Before buying or building, check the classification of your exact plot on georisques.gouv.fr: this is the benchmark level used by insurers and notaires. This ranking complements the decree history above: the hazard tells you what can happen, the decrees tell you what has already happened. If your house is in a high-exposure area and has come through several dry summers, the risk of damage is no longer a hypothesis – it is documented. ## What characterises Marseille from a building surveying perspective In Marseille, the rugged relief between the limestone hills of the northern quarters, the Huveaune valley and the coastal plain creates a mosaic of highly heterogeneous soils – and it is precisely this variability that troubles foundations. ProvenΓ§al villas and 1970s-80s buildings, put up in large numbers in residential neighbourhoods such as Mazargues, Sainte-Marguerite or towards the Saint-Loup hills, often rest on shallow foundations poorly suited to the swelling clays found in pockets beneath the surface fill. We are regularly called out to bungalows in this sector where the stock, designed at a time when soil surveys were not systematic, absorbs the shrink-swell cycles badly: the long, dry Marseille summers desiccate the clay, which contracts, then the autumn rains make it swell again, generating differential settlement that cracks bay-window corners and slab joints. Vegetation also plays a real part: Aleppo pines and olive trees planted close to homes, with their powerful root systems, dry the soil further during drought and amplify ground movements. Finally, the sustained property development of recent decades – many estates built on worked or sloping ground – heightens the risk, because earthworks disturb the natural water balance of clay soils and encourage cracks to appear on neighbouring buildings. ## 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: **2017**, with 390 mm over the year, against a local average of 613 mm. 2022 ranks as the 5th driest year out of 35 (421 mm against an average of 613 mm); 2023 follows in 7th place (431 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. ## Marseille: 43 Cat Nat decrees since 1982, in chronological order Each line = an event recognised by an interministerial decree published in the Official Gazette (GASPAR database): - πŸ”΅ **11/1982 β†’ 11/1982** – Floods (decree of 18/11/1982) - πŸ”΅ **11/1982 β†’ 11/1982** – Cyclones / Storms (decree of 18/11/1982) - πŸ”΅ **08/1986 β†’ 08/1986** – Floods (decree of 11/12/1986) - πŸ”΅ **01/1987** – Floods (decree of 02/12/1987) - πŸ”΅ **10/1988** – Floods (decree of 20/04/1989) - πŸ”΅ **02/1989 β†’ 02/1989** – Floods (decree of 13/06/1989) - πŸ”΄ **05/1989 β†’ 12/1991** – Drought (RGA – clay shrink-swell) (decree of 25/01/1993) - πŸ”΅ **09/1989 β†’ 09/1989** – Floods (decree of 08/01/1990) - πŸ”΅ **09/1991** – Floods (decree of 21/08/1992) - πŸ”΅ **10/1991 β†’ 10/1991** – Floods (decree of 21/09/1992) - πŸ”΄ **01/1992 β†’ 06/1993** – Drought (RGA – clay shrink-swell) (decree of 27/12/2000) - πŸ”΅ **06/1992** – Floods (decree of 04/02/1993) - πŸ”΅ **09/1993 β†’ 09/1993** – Floods (decree of 11/10/1993) - πŸ”΅ **08/1995 β†’ 08/1995** – Floods (decree of 08/01/1996) - πŸ”΅ **08/1996** – Floods (decree of 01/10/1996) - πŸ”΅ **10/1997** – Floods (decree of 12/03/1998) - πŸ”΄ **01/1998 β†’ 06/1998** – Drought (RGA – clay shrink-swell) (decree of 27/12/2000) - πŸ”΅ **09/1998** – Floods (decree of 29/12/1998) - πŸ”΅ **10/1999 β†’ 10/1999** – Floods (decree of 03/03/2000) - πŸ”΅ **09/2000** – Floods (decree of 06/11/2000) - πŸ”΄ **01/2002 β†’ 06/2002** – Drought (RGA – clay shrink-swell) (decree of 25/08/2004) - πŸ”΅ **12/2003 β†’ 12/2003** – Floods (decree of 12/12/2003) - πŸ”΄ **01/2004 β†’ 03/2004** – Drought (RGA – clay shrink-swell) (decree of 11/06/2008) - πŸ”΅ **09/2004** – Floods (decree of 11/01/2005) - πŸ”΄ **01/2005 β†’ 03/2005** – Drought (RGA – clay shrink-swell) (decree of 11/06/2008) - πŸ”΄ **01/2006 β†’ 03/2006** – Drought (RGA – clay shrink-swell) (decree of 11/06/2008) - πŸ”΄ **01/2007 β†’ 03/2007** – Drought (RGA – clay shrink-swell) (decree of 07/08/2008) - πŸ”΄ **07/2007 β†’ 09/2007** – Drought (RGA – clay shrink-swell) (decree of 07/08/2008) - πŸ”΄ **01/2008 β†’ 03/2008** – Drought (RGA – clay shrink-swell) (decree of 16/10/2009) - πŸ”΅ **12/2008** – Floods (decree of 17/04/2009) - πŸ”΅ **09/2009** – Floods (decree of 10/11/2009) - πŸ”΅ **10/2012** – Floods (decree of 20/02/2013) - πŸ”΅ **11/2012 β†’ 11/2012** – Floods (decree of 20/02/2013) - πŸ”΄ **07/2016 β†’ 09/2016** – Drought (RGA – clay shrink-swell) (decree of 25/07/2017) - πŸ”΄ **07/2017 β†’ 09/2017** – Drought (RGA – clay shrink-swell) (decree of 10/07/2018) - πŸ”΄ **07/2019 β†’ 09/2019** – Drought (RGA – clay shrink-swell) (decree of 28/07/2020) - πŸ”΅ **10/2019 β†’ 10/2019** – Floods (decree of 30/10/2019) - πŸ”΅ **10/2021 β†’ 10/2021** – Floods (decree of 15/10/2021) - πŸ”΄ **04/2022 β†’ 09/2022** – Drought (RGA – clay shrink-swell) (decree of 03/04/2023) - πŸ”΅ **08/2022** – Floods (decree of 18/09/2022) - πŸ”΄ **04/2023 β†’ 06/2023** – Drought (RGA – clay shrink-swell) (decree of 18/06/2024) - πŸ”΅ **09/2024** – Floods (decree of 15/12/2024) - πŸ”΅ **10/2024** – Floods (decree of 19/01/2025) **How an expert reads this**: 15 droughts and 28 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 Marseille **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, a wall that crumbles in Marseille. You may have read that resin injections are needed, or a mechanical ventilation system. Our advice: not so fast. Treating the wrong cause only moves the problem – and you will have paid for nothing. ### The four causes and how to recognise them - **Rising damp**: moisture climbs from the ground through the wall, usually stopping at 1-1.5 m, with irregular tide-mark staining. Frequent in the old buildings of the city centre with no damp-proof course. - **Water ingress**: water enters from outside (roof, cracked faΓ§ade, terrace, joinery). Stains often follow a precise path and worsen after rain. - **Condensation**: linked to inadequate ventilation, it mainly affects cold corners, bathrooms and kitchens with no extraction, with surface mould. - **Leak**: defective pipe, drain or seal. A localised stain, sometimes developing even in dry weather. ### The trap of the diagnosis sold by the treatment contractor In Marseille as elsewhere, many companies that carry out the diagnosis are also the ones selling and fitting the treatment. The conflict of interest is structural: the heavier and costlier the diagnosis concludes the treatment should be (injections, drainage, tanking), the higher the quotation that follows. A free quotation from a treatment contractor is never a neutral act – it is a sales tool. Before committing to works, have a diagnosis drawn up by an independent expert who sells no treatment and therefore has no interest in exaggerating the problem. It is the only way to know for certain what is actually causing your damp, and to avoid useless or unsuitable works. ## Why do cracks appear several months after the drought? Annual rainfall measured on the Marseille weather grid (Open-Meteo data): - 2019: 660 mm Β· 2020: 455 mm Β· 2021: 676 mm Β· 2022: 421 mm Β· 2023: 431 mm Β· 2024: 660 mm - **Average over the period: 550 mm/year**, the driest year being 2022 (421 mm) - Three markedly dry years (2020, 2022, 2023): 455 mm, 421 mm, then 431 mm - Last known year (2024): back to 660 mm Clay shrink-swell works in two stages: the drought dries the clay at depth, causing shrinkage and the first cracks, then the return of the rain abruptly rehydrates the ground and generates swelling – hence further differential movements. If your house was built between 1970 and 2000 on shallow foundations – as most villas in the region were – it takes the strain first, often 12 to 24 months after the dry episode. Remember this lag: a crack appearing today may well go back to the drought of a year or two ago. ## A crack in your house in Marseille: should you worry? - A **stair-step** crack, passing through the wall, open by more than 2 mm β†’ to be monitored without delay - A crack that **is evolving**: fit a tell-tale (plaster or gauge) and read it several months apart to document the progression - Associated signs to check inside the house: doors and windows that stick, floor tiles splitting diagonally, render that comes loose or bulges - Aggravating factors to look for around the house: clay ground, trees close to the foundations, failing drainage With 15 drought decrees on Marseille’s record, as soon as several of these signals stack up in your home, call an expert before any repair – and before any buying or selling decision, so as not to discover the problem after signing. ## Buying or selling a cracked house in Marseille: what recourse do you have? 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 buying, two remedies exist: - **Hidden defect** (vice cachΓ©, Article 1641 of the French Civil Code): serious cracks, not detectable at a viewing, predating the sale β†’ price reduction or cancellation of the sale, within 2 years of discovery - **Fraudulent concealment** (dol, Article 1137): the seller knew and hid the damage β†’ cancellation plus damages, within 5 years; the commune’s GASPAR decree then strengthens your file Before starting proceedings, have the damage dated by an independent expert: it is that survey which decides between hidden defect and fraudulent concealment, and which will carry weight with the judge or the insurer. On the legal side, instruct a French property lawyer. ## What actually happens during a drought/clay survey in Marseille? - Technical visit: crack mapping and classification, width measurements, functional disorders - Context analysis: clay zoning, the commune’s Cat Nat history (15 drought decrees), local drought episodes - Costing of repair works: underpinning, injections, drains – with several scenarios, from cheapest to most durable - A written report your insurer or lawyer can use directly to support your file Independent expert, with no ties whatsoever to a works company. [Request a visit in Marseille](https://cassini-expertise.fr/en-contact/) – also worth reading, our [complete guide to RGA and Cat Nat in the 06, 83 and 13](https://cassini-expertise.fr/en-cracks-subsidence-expert-french-riviera/). ## Soil surveys on clay ground: what the regulations say **The requirement for a prior geotechnical survey has applied since 1 October 2020 ([ELAN law](https://www.legifrance.gouv.fr/jorf/id/JORFTEXT000037639478), 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 Marseille (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**: Marseille 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](https://cassini-expertise.fr/en-contact/). ## Frequently asked questions ### Is Marseille in a clay risk zone? The Bouches-du-RhΓ΄ne is very largely covered by the clay shrink-swell hazard (BRGM mapping, consultable on georisques.gouv.fr). In Marseille, the GASPAR history with its 15 recognised drought decrees confirms the risk is very real, not merely theoretical. Check the classification of your exact plot before buying. ### Is my cracked house in Marseille eligible for natural disaster compensation? Only if your damage can be linked to a period covered by a decree (last recognised drought periods: 1993, 2000, 2004, 2008, 2009, 2017, 2018, 2020, 2023, 2024) and provided you declared within 30 days. Failing that, the action against the seller remains – and precisely dating the damage through a survey then becomes the heart of the matter. ### Can the figures 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 Marseille grid. Cassini Expertise does not touch this data. ## What is the rainfall situation? (as at 04/10/2026) In the commune: **recent rain (3 days ago)**. Rainfall over the last 30 days: **18 mm**, against roughly 55 mm expected at this time of year – a 67% 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. ## Weekly drought update (as at 05/10/2026) In the commune: **recent rain (4 days ago)**. Rainfall over the last 30 days: **18 mm**, against roughly 56 mm expected at this time of year – a 68% 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. ## Weekly drought update (as at 12/10/2026) In the commune: **recent rain (5 days ago)**. Rainfall over the last 30 days: **33 mm**, against roughly 61 mm expected at this time of year – a 46% 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. ## What is the rainfall situation today? (as at 19/10/2026) In the commune: **no notable rain for 12 days**. Rainfall over the last 30 days: **33 mm**, against roughly 66 mm expected at this time of year – a 50% 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. ## The water table against its historical record: what 29 years of measurements show 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 cachΓ©s), explained](https://cassini-expertise.fr/article-1641-code-civil-garantie-vices-caches/). --- Source : https://cassini-expertise.fr/en/marseille-clay-subsidence-cracks/