The weight of the house itself is particularly heavy, and the foundation is surrounded by reinforced concrete structures. Otherwise, the built house will sink, and high-rise buildings will have to pile and build houses on the piles. In this way, it is stable. People who pay attention to Feng Shui or believe in God and religion may quietly bury some ancient coins of the Five Emperors in the foundation.
You really don't need to put a few coins. It's a local custom.