Dark stains on your walls? Here’s what they reveal (and how to remove them)

where do these dark stains come from?
A wall turning black—especially in corners—is usually not just dirt. In most cases, excessive humidity is the culprit.

Poor ventilation in spaces like bathrooms, kitchens, or rarely opened bedrooms traps moisture. This leads to condensation on cold surfaces, creating an ideal environment for mold growth.

Other causes include:

External water infiltration (faulty gutters, damaged roof, rising damp).

Thermal bridges causing cold spots and condensation.

Furniture placed too close to walls, blocking air circulation.

According to ANAH, one in five French households faces persistent humidity problems.

immediate actions to stop the spread

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