Mould After a Bathroom Flood: Who to Call? Damp Expert Antibes

After a bathroom flood, the mould keeps coming back: the water is still inside the fabric

You had a leak or an overflow in the bathroom. The water was mopped up, but a few weeks later: odours, black stains on the walls, wallpaper lifting, darkening tile joints. The mould does not go away, and returns after every clean.

This is not a surface problem. Residual water is still inside the walls, the skirting boards, the floor screed and the joints. What you need is an independent building expert who measures that material moisture precisely with a moisture meter – not just another clean.

Why the mould persists and keeps returning

The mechanism is always the same:

• Incomplete drying. After the flood, the air was dried (with a dehumidifier), but not the materials. Walls behave like a sponge: water rises by capillary action into the structure, the mortar, the concrete, the brick. That takes 3 to 8 weeks depending on thickness and material.
• Paint or finish applied too early. The room is repainted, new tiles laid, new skirting fitted on walls or screeds that are still damp. The finish traps the water inside: mould finds an ideal medium there (darkness, material moisture above roughly 65 % in porous finishes).
• Absorbent materials kept. Skirting boards, sealant and joints have held water – even the wood of door frames. Once material moisture passes 15-18 % in timber or 20-25 % in concrete, fungus colonises.
• Insufficient ventilation during drying. If the mechanical ventilation is closed off or absent, air does not circulate: water stagnates in the room and in the pores of the materials.

The result: you go back to the insurer, the insurer says “that’s cleaning, not works”, the contractor says “not our responsibility” – and you are left with damp walls and growing mould.

What a building expert measures after a flood

You need a quantified moisture survey, point by point:

• Capacitive or resistive moisture meter. We measure moisture inside the walls (not just the surface). 10 to 30 readings per room: skirting boards, wall bases, corners, ceiling, window reveals, tile joints, floor screed.
• Moisture mapping in %. You get a dated plan showing: dry areas (under 12 %), damp areas (15-20 %), very damp areas (over 20 %). That objectively proves the condition.
• Thermal camera. To locate where the water has pooled: under a tiled floor, behind a skirting board, rising damp from the foundations, a cold thermal bridge acting as a condensation pocket.
• Ventilation check (anemometer). We measure the extract airflow. A blocked or undersized system slows drying and feeds condensation.
• Comparative analysis. We benchmark against normal values for the region (Antibes, the Var, the Alpes-Maritimes): on the Mediterranean coast in summer, 45-50 % relative humidity is normal; beyond that, it is not.
• Source determination. Where the claim is disputed (leak from the flat above? rising damp? failed waterproofing behind the tiles?), we locate the origin.

The survey is dated, signed and photographed. It is evidence that the damage persists.

Who pays for drying and reinstatement

If the water damage was declared to the insurer

• The insurer covers drying and reinstatement works (paint, tiling, skirting) – but only on the basis of its approved contractors’ quotes.
• If the insurer appointed a drying company and the job was botched (residual moisture never measured, site closed early), the remedial works fall to that company under its warranty (Article 1792 of the Civil Code regime for works). A moisture survey proves it.
• If the insurer refuses to fund the reinstatement saying “the earlier works are closed”, you argue the hidden defect: residual moisture unknown at the time the file was closed. The insurer must reopen it.

If the leak comes from the shared building (common parts)

• Article 9 of the 1965 Act: the residents’ association (syndicat) is responsible for maintaining common parts. The association’s building insurance covers the damage.
• If the association refuses, claim first under your own water-damage cover (excess applies), then recover from the syndicat and its insurer.

If the leak comes from the flat above (a neighbour)

• The neighbour’s insurer is liable. You declare a claim; the two insurers coordinate.
• A frequent sticking point: “our insurer says it’s your insulation, not the leak”. An independent moisture survey settles it: water found up to 50 cm high on the wall comes from above.

The trap of the premature closure: when the insurer shuts the file too early

Typical sequence:

1. Flood reported on a Monday.
2. Insurer sends the drying contractor on Thursday; site closed on Friday (5 days).
3. Insurer says: “fine, the walls will dry naturally, no survey needed”.
4. File closed on the basis of the quote.
5. Four months later: odours, black mould under the wallpaper, salt efflorescence on the plaster. You call the insurer again.
6. The reply: “sorry, the file has been closed since October. It is no longer our concern”.

How to avoid it: have the residual moisture measured by an independent expert BEFORE the file is closed. If the walls are at 22 % material moisture, the survey proves it. The insurer cannot close the file; it must fund the additional drying.

The earlier the measurement, the harder the file is to challenge.

Do not confuse: dry air is not dry materials

A common trap: a dehumidifier is installed, relative humidity drops from 95 % to 50 %. Everything seems fine. But the walls are still at 25-30 % material moisture. Dry air alone cannot extract capillary water from the core of the materials. It takes time (progressive release), genuine ventilation and airflow across the damp surfaces. Dehumidifiers by themselves cannot dry a thick wall in under 3 to 4 weeks.

A point that protects you: Cassini Expertise carries out no repair works and sells no equipment (ventilation, water-repellent treatment, drying kit). The firm has no financial interest in its conclusions: it diagnoses, identifies the source and writes the report – a neutrality your insurer, your syndic or a court can rely on.

Field experience that makes the difference

Cassini Expertise draws on fifteen years spent on public works sites and in project management: drying a building is lived experience, not theory.

Four frequently asked questions

Is mould after a flood dangerous to health?

Yes. Mould releases spores and mycotoxins. Prolonged inhalation causes respiratory symptoms, allergies, worsened asthma and, in immunocompromised people, fungal infections. Exposure is riskier in confined spaces (a bathroom without ventilation). The source – the moisture in the walls – must be removed, not just the stains cleaned.

Must everything be stripped and redone (walls, tiling, skirting)?

Not systematically. It depends on residual moisture levels and materials:

• tiled floor on screed: if the screed is at 18 % moisture, the tiles can stay but the adhesive bed must be redone, as the old one will have swelled;
• skirting boards: timber or MDF above 20 % must be replaced (rot risk);
• plaster walls or render: if the plaster has swollen, new render is required;
• silicone joints: to be redone, as they hold water and grow mould.

An expert measures and recommends exactly what to change and what to keep.

How long does a wall take to dry completely after a flood?

Rules of thumb for the Mediterranean climate (Antibes, the Var):

• plaster or render, 10 cm thick: 3 to 4 weeks;
• concrete screed, 5-8 cm: 4 to 6 weeks;
• thick walls (stone, solid brick): 2 to 3 months;
• with active ventilation (dehumidifier plus mechanical ventilation): 30-40 % faster.

Temperature matters: summer (25-30 °C) dries faster; winter (10-15 °C) is very slow. Measure regularly (every 10 days) to track the drying curve.

The insurer refuses the mould reinstatement: what then?

• Ask for the grounds of the refusal in writing.
• Commission an independent moisture survey: quantified proof that residual moisture persists.
• Send the report to the insurer by registered letter: “The mould is the direct consequence of the incomplete drying of the declared claim. Article L. 113-2 of the Insurance Code binds you to cover the consequences of the claim.”
• If the refusal stands, refer the matter to the insurance mediator (free) or litigate.
• Keep every document: dated mould photographs, cleaning invoices, correspondence with the insurer.

Antibes, the Var, the Alpes-Maritimes: call an independent expert now

Bathroom mould that keeps returning after a flood? Do not let the insurer close the file without a survey.

Cassini Expertise works in Antibes and across the Var and the Alpes-Maritimes (Nice, Grasse, Toulon). A building expert on insurance claims, with fifteen years of project management experience. We measure residual moisture, locate hidden water, document the condition and produce reports insurers accept. Reply within 24 working hours; written report within 2 to 5 working days.

Phone: 04 22 46 06 04 – email: contact@cassini-expertise.fr

Also read

• Bathroom humidity: landlord, managing agent or tenant responsibility
• Mould on walls: condensation or infiltration?
• Damp stain on the ceiling: where does it come from and what to do

Further reading: Mould Returning in Your Wardrobes After Painting? The Real Fix · Persistent House Odours With Normal CO2 and Humidity Levels

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.