Salon-de-Provence: Clay Soil, Subsidence and Cracks – Official Data

The geological and climate context of Salon-de-Provence

Your house is cracking in Salon-de-Provence? The GASPAR database lists 2 drought decrees (full list below) and 7 flood decrees, i.e. 9 decrees in all – the local clay soil is a recognised factor in these disorders. The rainfall tells the same story: three dry years (2020, 2022, 2023), then a rebound to 839 mm in 2024 – precisely the scenario that puts foundations to work in Nostradamus’s town.

Cassini Expertise, an independent building expert, handles drought-related cracks and damage in Salon-de-Provence and across the whole of the 13. This page brings together the commune’s official data, to help you work out whether your case is documented – and what to do next.

Salon-de-Provence: drought, clay and cracks – what the official data says

According to GASPAR (decrees published in the Official Gazette since 1982), the commune has recorded a total of 9 natural disaster decrees:

• 2 drought decrees (differential ground movement linked to clay shrink-swell)
  • event of 01/07/2019 (decree of 29/04/2020)
  • event of 31/03/2023 (decree of 24/03/2025)
• 7 flood and storm decrees

What to take from it: each drought decree covers a precise window of dates. If your cracks appeared (or worsened) during one of these two periods, keep your dated photographs and invoices – they are the basis of a solid Cat Nat file. If not, do not throw anything away either: the hidden-defect or fraudulent-concealment route against the seller remains, and there too the dating of the damage will be your best piece of evidence.

What the official clay mapping says

The GéoRisques platform (BRGM) classifies Salon-de-Provence at high exposure to clay shrink-swell, with some sectors at medium exposure. This is the benchmark level your insurer and notaire already consult to assess the risk on your plot – you can check the exact address on georisques.gouv.fr.

In practical terms: 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 been through one or more dry summers, the risk of damage is no longer a hypothesis – it is documented. All the more reason to monitor how any crack evolves, even a small one.

What characterises Salon-de-Provence from a building surveying perspective

In Salon-de-Provence, we are regularly called to clay-soil disorders affecting both the 1970s-80s villas built on shallow foundations in the estates around the old centre and the more recent constructions of the bungalow zones that developed towards Lançon or on the edge of the commune, between plain and foothills. The sector, marked by contrasted relief between the hills of the Crau and the agricultural plain, has soils particularly sensitive to shrink-swell: the clay contracts sharply during the summer drought typical of the Provençal climate, then swells again with the autumn rains, generating differential settlement under the foundations. The phenomenon is frequently aggravated by pines and oaks planted too close to homes, whose powerful root systems dry the soil at depth and amplify ground movements. Traditional Provençal stone houses, often built with no thorough soil survey at the time, show characteristic façade cracks, notably at corners and above openings. Renovations and extensions carried out on this older stock, without adapting the original foundations, weaken further structures already subjected to these geotechnical constraints specific to the Salonais area.

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 399 mm over the year, against a local average of 667 mm. 2022 ranks as the 6th driest year out of 35 (492 mm against an average of 667 mm); 2023 follows in 10th place (543 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.

Salon-de-Provence: 9 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 – Floods (decree of 18/11/1982)
• 🔵 11/1982 → 11/1982 – Cyclones / Storms (decree of 18/11/1982)
• 🔵 08/1986 → 08/1986 – Floods (decree of 11/12/1986)
• 🔵 07/1987 → 07/1987 – Floods (decree of 02/12/1987)
• 🔵 10/1994 → 10/1994 – Floods (decree of 21/11/1994)
• 🔵 11/2014 → 11/2014 – Floods (decree of 27/04/2015)
• 🔴 07/2019 → 09/2019 – Drought (RGA – clay shrink-swell) (decree of 29/04/2020)
• 🔵 08/2021 – Floods (decree of 24/09/2021)
• 🔴 03/2023 → 06/2023 – Drought (RGA – clay shrink-swell) (decree of 24/03/2025)

How an expert reads this: 2 droughts and 7 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 Salon-de-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.

In Salon-de-Provence, the marly subsoil and the old houses of the town centre favour several types of damp that look alike to the eye but have nothing in common when it comes to treatment. Before signing an injection or ventilation quotation, the true cause must be identified.

The four causes and how to recognise them

• Rising damp: stains climbing from the ground over 1 to 1.5 m, saltpetre, render that blisters low on the walls, often in older houses.
• Water ingress: a localised halo linked to rain, often near a roof, a cracked façade or a poorly waterproofed balcony; worsens after a rain episode.
• Condensation: streaming windows, mould in room corners or behind furniture, linked to a lack of ventilation, not to the state of the wall.
• Leak: a pinpoint stain that reappears quickly after drying out, often near a pipe run, bathroom or kitchen.

The trap of the diagnosis sold by the treatment contractor

Many injection companies in Salon-de-Provence offer a “free quotation” – but it is the same salesperson who then sells you the treatment. The diagnosis almost always concludes rising damp, even when the real cause is condensation or a water ingress that costs 200 euros to fix. The result: several thousand euros of resin injections applied to a wall that will stay damp as long as the true cause is untreated.

Before committing to works, have an independent diagnosis drawn up, with no commercial ties to a treatment contractor. Contact us for an on-site survey in Salon-de-Provence. To go further on diagnostic and treatment methods, see the damp guide for the 06, 83 and 13.

Why do cracks appear several months after the drought?

Annual rainfall measured on the Salon-de-Provence weather grid (Open-Meteo data):

• 2019: 769 mm · 2020: 530 mm · 2021: 789 mm · 2022: 492 mm · 2023: 543 mm · 2024: 839 mm
• Average over the period: 660 mm/year, driest year: 2022 (492 mm)
• Three years below average (2020, 2022, 2023): 530 mm, 492 mm then 543 mm
• Then 2024 bounces back to 839 mm, +27% against the average

Clay shrink-swell plays out in two stages: first the drought dries the clay at depth – shrinkage, first cracks – then the return of the rains rehydrates the ground in one go – swelling, differential movements. If your house has shallow foundations (the case for most villas built between 1970 and 2000), it is hit first, with a lag of 12 to 24 months after the dry episode. In other words: a crack appearing today may well date from the 2022-2023 drought.

Which cracks should you monitor, and which should alert you at once?

• A stair-step crack, passing through the wall, open by more than 2 mm
• A crack that is moving (fit a tell-tale – a simple pencil mark or plaster band – and check it several months apart)
• Associated signs to watch at the same time: doors and windows that stick, floor tiles splitting diagonally, render that bulges
• Aggravating factors on your land: clay soil, trees close to the house, failing drainage

With 2 drought decrees already recognised for the commune, as soon as you stack up several of these signs, call an expert before launching works – and before any buying or selling decision. A repair carried out without a diagnosis can mask the problem without solving it.

Buying or selling a cracked house in Salon-de-Provence: 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, you have two levers:

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

In both cases, an expert report dating the appearance of the cracks is the central piece of the file. On the strategy to follow, instruct a French property lawyer.

What actually happens during a drought/clay survey in Salon-de-Provence?

• Technical visit: crack mapping and classification, width measurements, functional disorders
• Context analysis: clay zoning, the commune’s Cat Nat history (2 drought decrees), local dry periods
• Costing of repair works: underpinning, injections, drains – with several scenarios to suit your budget
• A written report directly usable by your insurer or your lawyer

Independent expert, with no ties to any works company – and therefore no interest in selling you a repair. Request a visit in Salon-de-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 Salon-de-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: Salon-de-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, counter-surveys. Request a consultation.

Frequently asked questions

Is Salon-de-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 Salon-de-Provence, the 2 drought decrees recognised under GASPAR confirm the risk is nothing theoretical: if you own a property here, check your exact exposure on the site before playing down a crack.

Does a cracked house in Salon-de-Provence entitle the owner to Cat Nat compensation?

Only if your damage can be linked to a period covered by a decree (the last two recognised periods: 2020, 2025) and if you made your declaration within 30 days. Otherwise, you must turn to the seller – and that is where dating the damage through a survey becomes decisive for your file.

Can the figures on this page be verified?

Yes: the decrees come from the GASPAR database (Official Gazette, open data, 2025 update), the rainfall from the Open-Meteo weather archives for the Salon-de-Provence grid. Cassini Expertise reports this data exactly as it stands, without adjusting it.

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

In the commune: recent rain (4 days ago). Rainfall over the last 30 days: 37 mm, against roughly 58 mm expected at this time of year – a 36% 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 12/10/2026)

In the commune: recent rain (5 days ago). Rainfall over the last 30 days: 37 mm, against roughly 62 mm expected at this time of year – a 40% 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: 38 mm, against roughly 66 mm expected at this time of year – a 42% 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 24 years of measurements show

The reference piezometric station for the sector (002EXHX) has been monitoring the water table since 2003 – 24 years of records. As at 02/10/2026, the mean level over the last thirty days is 17.61 m NGF. Across the whole record, the water table has spent only 52.0% of its time below this level: a level close to the station’s average.

• Last comparable episode: 03/10/2024 – 2.0 years ago
• Frequency: 56 similar episodes recorded since 2003, i.e. a return every year on average – in hydrologists’ language, an intermediate episode
• Historical minimum: 16.71 m NGF, reached on 20/02/2012

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.