After a bit of research—and a fair amount of overthinking—we finally started getting closer to an explanation.
We looked at mold types. We checked insect-related causes. We even considered structural issues in the wall or tile adhesive problems.
But nothing quite matched what we were seeing.
Then we came across something that finally made sense… and at the same time made everything even more surprising.
The Real Explanation: Plant Roots
It turns out, it wasn’t mold.
And it wasn’t insects either.
It was actually plant roots.
Yes—real roots.
Most likely, they came from a tree or plant outside the building (or possibly even from vegetation growing beneath or nearby the structure). Over time, they found a tiny crack or gap in the construction.
