Do you live in a building built before 1920? Its foundation is almost certainly made up of superimposed rubble and bound with lime. While your foundation may be extremely solid, with the years the mortar between the stones breaks down resulting in water seepage, excess moisture, and mould.
Even if this has happened, rest assured that there probably is still time to repair your foundation without having to replace it completely. To avoid the high cost of replacing your foundation, act now.