ᐅ Mold in the Home

Hello everyone, I’m new here. What I’m writing about is certainly a very old topic because affected tenants usually believe they are not doing anything wrong. The building was constructed around 1914-1920; it is a three-unit house, and the middle apartment has mold issues. It’s clear that the problem is caused by not ventilating or insufficient ventilation, which can be observed. The tenants claim, for example, that the house has cracks—probably shrinkage cracks—through which rainwater penetrates the interior wall, according to their statement. However, the wall is about 43 cm (17 inches) thick and likely includes an air cavity. Assuming rainwater were to penetrate the exterior wall, my amateur theory is that the water would run down inside the air cavity because it seems unlikely that water would move horizontally from the outer wall, through the air cavity, and into the interior wall. The existence of an air cavity is suspected by consulted professionals, such as a painter, a civil engineer, and a building renovator, all experts in their fields. If there were no air cavity, how could the masonry be about 43 cm (17 inches) thick, and how could moisture penetrate through such thick masonry? As mentioned at the beginning, there really is only one explanation: the space is not ventilated (properly). I would like to hear or read opinions from this forum. Many thanks in advance.

Have the professionals already measured the moisture in the walls or inspected the issue on site?

Yes, upon inspection and measurements, the water pipes are leaking, and there is moisture inside the house, which can be caused by water supply (e.g., washing machine) or water drainage. All results are negative.