[bipson]

Oh, they do.

Concrete has great thermodynamic properties for living comfort. It cools at day, warms at night, transfers from cold parts of the house to hot ones, etc.

It is there on purpose (and not too difficult to drill into with a "Bohrhammer", rotary drill(?), i.e. the ones with SDS(+)).

Actually, the brick-walls we have (hollow bricks with flimsy thin walls) were harder for me to figure out. They need really careful drilling with the right tools, otherwise the brick shatters and nothing will take grip.