One is that there is a small house with a roof in the big house. This small house must be the kind that people moved. Buildings with roofs or shrines are not included.
The other is that the foundation of the old house was not cleaned up, and the new house was built outside the foundation of the old house. Building a house, laying a foundation and building a house are all major events and must be sacrificed. The old foundation is directly surrounded by the new foundation, which is a great disadvantage in geomantic omen.
A big house with a small house, from the perspective of geomantic omen, is a big evil, but it is a bad thing. Pay attention.